03 Atomic Theory Concept Overview
ATOMIC THEORY | CONCEPT OVERVIEW The TOPIC of ATOMIC THEORY is not directly provided to us in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. However, it is of upmost importance that we understand the fundamental concepts and applications revolving around this subject independent of the NCEES Supplied Reference Handbook.
CONCEPT INTRO: CHEMISTRY is the study of MATTER and the CHANGES it undergoes with respect to PHYSICAL PROPERTIES, COMPOSITION, and CHEMICAL STRUCTURE. A PHASE is a HOMOGENEOUS STATE of a SUBSTANCE with UNIFORM physical and chemical characteristics. There are THREE possible STATES or PHASES of MATTER that exist (GAS, LIQUID, or SOLID), depending on the TEMPERATURE, PRESSURE, and COMPOSITION of the SUBSTANCE. A PHASE CHANGE is the change of a SUBSTANCEβS MATTER from one PHYSICAL STATE to another due to conditions such as PRESSURE, VOLUME, or TEMPERATURE. A GAS has NO definite SHAPE or VOLUME, and is classified as being easily COMPRESSIBLE. Made with
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A LIQUID has CONSTANT VOLUME and is classified as having NO definite SHAPE, being slightly COMPRESSIBLE. A SOLID has DEFINITE VOLUME and SHAPE, and is classified as being RIGID and DIFFICULT to COMPRESS. A SUBSTANCE is a FORM of MATTER that has a definite COMPOSITION and distinct PROPERTIES, such that a SUBSTANCE is classified as either an ELEMENT or a COMPOUND. An ISOTROPIC SUBSTANCE is a SUBSTANCE that has the SAME PHYSICAL PROPERTIES in ALL DIRECTIONS. All MATTER is CLASSIFIED as either a MIXTURE or a PURE SUBSTANCE. A MIXTURE is a combination of TWO or more SUBSTANCES are PHYSICALLY BONDED, in which the substances retain their distinct identities, and is classified as either HOMOGENEOUS or HETEROGENEOUS. Any MIXTURE can be CREATED and then SEPARATED by PHYSICAL MEANTS into individual PURE SUBSTANCES without changing the PROPERTIES or IDENTITY of the COMPONENTS. A HOMOGENEOUS MIXTURE is a MIXTURE that has a UNIFORM or HOMOGENEOUS composition throughout the mixture, with the COMPOSITION remaining CONSTANT.
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A HETEROGENEOUS MIXTURE is a MIXTURE that a NON-UNIFORM or HETEROGENEOUS composition throughout the mixture, with the COMPOSITION varying. For example, in a MIXTURE of SUGAR WATER, the SUGAR can be removed from WATER solution by heating the solution and EVAPORATING the WATER from the solution. Thus the SUGAR and WATER are PHYSICALLY SEPARATED. A PURE SUBSTANCE is a SUBSTANCE that cannot be SEPARATED into COMPONENTS by PHYSICAL MEANS, and retains its CHEMICAL COMPOSITION through all THREE PHRASES. An ELEMENT is a PURE SUBSTANCE that is composed of only ONE type of ATOM that has identical CHEMICAL PROPERTIES, having the same SIZE, MASS, and CHEMICAL MAKEUP. A COMPOUND is a PURE SUBSTANCE comprised of ATOMS from two or more ELEMENTS are CHEMICALLY COMBINED in FIXED RATIOS. An example of a COMPOUND is CARBON DIOXIDE which is always COMPOSED of MOLECULES with TWO ATOMS of OXYGEN for every ONE ATOM of CARBON. In any COMPOUND, the RATIO of the numbers of ATOMS of any two of the ELEMENTS present is either an integer or a simple fraction.
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Unlike MIXTURES, COMPOUNDS can be separated into their BASE ELEMENTS by CHEMICAL MEANS into their PURE COMPONENTS. ATOMIC STRUCTURE: The TOPIC of ELECTRON CONFIGURATIONS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. ATOMS are the BUILDING BLOCKS of matter, and define the PROPERTIES and BEHAVIORS of an ELEMENTS. Atoms of one ELEMENT are IDENTICAL in MASS and other PROPERTIES, and cannot be CONVERTED into atoms of another ELEMENT. MATTER is composed of ATOMS that are ELECTRICALLY CHARGED in one of two ways, either being POSITIVELY CHARGED (+) or NEGATIVELY CHARGED (-). ELECTROMAGNETIC FORCES or COULOMBIC FORCES are forces that cause atoms to be ATTRACTED to other ATOMS as a result of ELECTRIC POLARITIES and ELECTROSTATIC INTERACTIONS. ELECTROSTATIC FORCES can provide an ATTRACTIVE FORCE or a REPULSIVE FORCE based on the ELECTRICAL CHARGE on each of the ATOMS.
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An ATOM is composed of a central core NUCLEUS that is surrounded by NEGATIVELY CHARGED ELECTRONS (π β ). Within the NUCLEUS, an ATOM contains POSITIVE CHARGED PROTONS and NEUTRALLY CHARGED NEUTRONS. An ELECTRON is a NEGATIVELY charged particle, the magnitude of whose CHARGE is EQUAL to that of the PROTON. A PROTON is a POSITIVELY charged particle, the magnitude of whose CHARGE is EQUAL to that of the ELECTRON. A NEUTRON is an ELECTRICALLY NEUTRAL particle, neither positively nor negatively charged, whose MASS can be taken EQUAL to that of the PROTON. An ATOM has no charge and is considered NEUTRAL, such that it contains an EQUAL number of PROTONS and ELECTRONS, which provide an EQUIVALENT number of POSITIVE and NEGATIVE charges resulting in a net ELECTRICAL CHARGE of ZERO. CHEMICAL REACTIONS involve either the TRANSFER or the SHARING of ELECTRONS between ATOMS. Therefore, we can say that the CHEMICAL REACTIVITY of an atom is DEPENDENT upon the number of ELECTRONS and PROTONS, and is INDEPENDENT of the number of NEUTRONS.
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The BOHR MODEL uses the terms ENERGY LEVELS, ORBITALS, or SHELLS to describe the SEPARATION of differing ENERGY LEVELS of ELECTRONS around the NUCLEUS of the ATOM. The TOPIC of the PHOTOELECTRIC EFFECT can be referenced under the SUBJECT of MATERIALS SCIENCE on page 60 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A PHOTON is the AMOUNT of ENERGY released if an ELECTRON moves from a HIGHER ENERGY SHELL to the next LOWER ENERGY SHELL. The PHOTOELECTRIC EFFECT is an occurrence where ELECTRONS are EMITTED from MATTER as RESULT of their ABSORPTION of ENERGY from ELECTROMAGNETIC RADIATION.
The ENERGY LEVEL an electron normally occupies is called its GROUND STATE. Made with
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However, it can move to a HIGHER-ENERGY, LESS-STABLE orbital, or SHELL, by ABSORBING ENERGY. The EXCITED STATE is the HIGHER ENERGY and LESS STABLE orbital of the ATOM, AND enables EASY removal or transfer of an ELECTRON from ONE ENERGY LEVEL to another. After an ELECTRON is done being EXCITED, the ELECTRON can return to its original GROUND STATE by RELEASING the ENERGY it has ABSORBED. This happens because of the effect of ELECTRON REPULSION also known as ELECTRON SHIELDING, which is a result of the ELECTRON being attracted to the POSITIVE CHARGE of the NUCLEUS. ELECTRONS that are on the OUTERMOST ENERGY LEVEL are commonly referred to as VALENCE ELECTRONS. One of the properties that ELEMENTS within a GROUP share is the tendency to gain or lose a specific number of VALENCE ELECTRONS, which is referred to as the VALENCE or VALENCE STATE. For some elements, the number of electrons that can be naturally gained or lost is nonspecific and can change depending on the circumstances. These elements are said to have a MULTI-VALENCE STATE.
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ELECTRON CONFIGURATIONS: The TOPIC of ELECTRON CONFIGURATIONS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. In chemistry, we often like to know the LOCATION of an ELECTRON relative to the ENERGY LEVEL or ORBITAL of the ATOMβS NUCLEUS. A useful way of doing this is to determine the ELECTRON CONFIGURATION of an ATOM, which will define the ADDRESS of each ELECTRON in the ATOM. The ELECTRON CONFIGURATION is the STANDARD NOTATION, also known as ORBITAL NOTATION, used to DESCRIBE the ELECTRONIC STRUCTURE of an ATOM. The ELECTRON CONFIGURATION of an ELEMENT aids in PREDICTING how ATOMS will join together to form CHEMICAL BONDS and how ELECTRONS define the CHARACTERISTICS of an ELEMENT. The PAULI EXCLUSION PRINCIPLE states that ELECTRONS occupy ENERGY LEVELS in such a way that no more than TWO ELECTRONS can occupy the same ORBITAL, and both ELECTRONS must have OPPOSITE MANGETIC SPINS relative to each other.
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Within the ORBITAL or ENERGY LEVEL designated by each value of βπβ, there is further QUANTIZATION of ENERGY, indicated by the letters βπ , π, π, πππ πβ in ORDER of INCREASING ENERGY.
Electron Configuration of Elements Shell
π
π
Element
s
s
p
Hydrogen
1
Helium
2
Carbon
2
2
2
Nitrogen
2
2
3
Oxygen
2
2
4
Sodium
2
2
6
1
Aluminum
2
2
6
2
1
Chlorine
2
2
6
2
5
Iron
2
2
6
2
Copper
2
2
6
Cadmium
2
2
Xenon
2
Gold
2
π s
p
π d
s
6
6
2
2
6
10
1
6
2
6
10
2
6
2
6
2
6
2
6
π
p
d
f
2
6
10
2
10
2
6
10
2
6
10
2
6
10
2
6
14
s
p
d
f
10
Each numbered ROW of the PERIODIC TABLE corresponds to a different principal ENERGY LEVEL, with higher numbers indicating higher energy. In each electron configuration, the magnitude of βπβ is given first, followed by the designation of βπ ,β and, if appropriate, of βπβ and βπβ. Made with
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The NUMBER of ELECTRONS within each orbital designation is shown as a SUPERSCRIPT. The sum of the SUPERSCRIPTS is, therefore, the number of ELECTRONS in the ATOMS. PERIODIC TABLE: The REFERENCE for the PERIODIC TABLE can be referenced under the SUBJECT of CHEMISTRY on page 55 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. The PERIODIC TABLE is a TABULAR ARRANGEMENT of the CHEMICAL ELEMENTS the associated ATOMIC NUMBER, SYMBOL, and ATOMIC WEIGHT of each ELEMENT. The CHEMICAL IDENTITY of an ATOM can be determined from EVALUATING the ATOMIC NUMBER and ATOMIC WEIGHT, and cross-referencing those values with the PERIODIC TABLE.
The ATOMIC NUMBER of an ELEMENT is the NUMBER of PROTONS in the NUCLEUS of each atom of an ELEMENT. Made with
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The ATOMIC NUMBER is a POSITIVE INTEGER beginning at 1 for Hydrogen and increases, by 1, for each subsequent atom. Thus, the ATOMIC NUMBERS of Hydrogen, Helium, Sodium, Aluminum, and Oxygen are, respectively, 1, 2, 11, 13, and 8. In a NEUTRAL ATOM, the number of PROTONS is EQUAL to the number of ELECTRONS, so the ATOMIC NUMBER also indicates the number of ELECTRONS present in the ELEMENT. The CHEMICAL SYMBOL is a one- or two- letter ABBREVIATION assigned to each ELEMENT based on the NAME of the ELEMENT. Some CHEMICAL SYMBOLS are based on the LATIN or GERMAN name of the element, so donβt always assume with the first one- or two- letters. The REFERENCE for the PROPERTIES OF METALS can be referenced under the SUBJECT of MATERIALS SCIENCE on page 61 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. For the purposes of the FE Exam, it is not worth your time to MEMORIZE the SYMBOL for every ELEMENT. Instead I would recommend you become FAMILIAR with the TABLE of the PROPERTIES of METALS in the REFERENCE HANDBOOK, which lists the METAL NAME and CHEMICAL SYMBOL for a variety of ELEMENTS.
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On this TABLE, you will find the METAL NAME and CHEMICAL SYMBOL, which you can use to help ELIMINATE answer choices within PROBLEMS.
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The ATOMIC WEIGHT, also known as the ATOMIC MASS NUMBER is the TOTAL NUMBER of NEUTRONS and PROTONS present in the NUCLEUS of an atom of an element, and is calculated as: πππ π ππ’ππππ = π΄π‘ππππ ππ’ππππ + πππ’π‘ππππ = ππππ‘πππ + πππ’π‘ππππ ATOMIC WEIGHT in CHEMISTRY represents the AVERAGE WEIGHT of all naturally occurring ISOTOPES of an ELEMENT and is given in units of ATOMIC MASS UNITS (amu) or GRAMS (g), where one ATOMIC MASS UNIT (AMU) represents: 1 πππ’ = 1.66 Γ 10β27 ππ 1
By definition, an ATOMIC MASS UNIT (amu) is 12 of the MASS of the CARBON-12 ISOTOPE that has SIX PROTONS and SIX NEUTRONS, C12 . ISOTOPES are ATOMS of the same ELEMENT with the SAME NUMBER of PROTONS, but a different ATOMIC MASS NUMBER resulting from a DIFFERENCE in the varying number of NEUTRONS. ATOMS of the DIFFERENT ISOTOPES of an ELEMENT are DISTINGUISHED by using the MASS NUMBER as a SUPERSCRIPT to the left of the ELEMENT SYMBOL. For example, 14 N and 15 N are both ISOTOPES of NITROGEN because they have the same PROTON NUMBER, but have differing MASS NUMBERS representing the SUM of the PROTONS and NEUTRONS in each particular ISOTOPE.
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The FORMULA to CALCULATE AVERAGE ATOMIC MASS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. To calculate the AVERAGE ATOMIC MASS from the known ISOTOPES of a given element, we use the equation for WEIGHTED AVERAGE based on the ABUNDANCE of each ISOTOPE: π΄π£πππππ π΄π‘ππππ πππ π = β(ππΌ Γ π΄πΌ )π Where: β’ ππΌ represents the MASS of the ISOTOPE β’ π΄πΌ represents the ABUNDANCE of the ISOTOPE, and WEIGHT of the AVERAGE β’ π is the NUMBER of ISOTOPES Each ISOTOPE has its own ABUNDANCE in NATURE, where the PERCENT ABUNDANCES of all the ISOTOPES of an ELEMENT have to equal 100%. ATOMIC BONDING: The TOPIC of ATOMIC BONDING can be referenced under the SUBJECT of MATERIALS SCIENCE on page 60 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. The BEHAVIOR of a SUBSTANCE is defined by the TYPE of CHEMICAL BONDS that define the STRUCTURE of the ATOMS comprising the SUBSTANCE. Made with
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A MOLECULE represents the SMALLEST PARTICLE of a particular ELEMENT or COMPOUND that can EXIST and RETAIN the CHEMICAL properties. When two elements interact, it is the OUTER ELECTRONS known as the VALENCE ELECTRONS, that are involved in the formation of CHEMICAL BONDS. MOLECULES are combinations of ATOMS bonded TOGETHER by IONIC and COVALENT BONDS. In forming COVALENT BONDS, elements are looking to make their OUTER SHELL of ELECTRONS totally full by SHARING valence electrons between ATOMS. COVALENT BONDS are the STRONGEST ATTRACTIVE FORCES typically FORMED between ATOMS with half-filled ORBITALS, as well as between NON-METALS, or between NON-METALS and METALLOIDS. The NUMBER of ELECTRONS shared is usually enough to fill the outermost VALENCE SHELLS and thus bring both atoms to their NOBLE GAS CONFIGURATION.
IONIC BONDING is based on the ELECTROSTATIC or COULOMBIC ATTRACTION between opposite ELECTRICALLY CHARGED ions, and the TRANSFER of ONE or more ELECTRONS from one ATOM to another. IONS are CHARGED ATOMS that LOST or GAINED ELECTRONS, resulting in a net ELECTRICAL charge NOT EQUAL to ZERO. Made with
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In forming IONIC BONDS, elements are looking to make their OUTER SHELL of ELECTRONS either totally FULL, or totally EMPTY, by either LOSING or GAINING valence electrons. A CATION is a POSITIVE ION that has ACCEPTED extra ELECTRONS, resulting in an ATOMIC STRUCTURE that is POSITIVELY CHARGED. An ANION is a NEGATIVE ION that has DONATED extra ELECTRONS, resulting in an ATOMIC STRUCTURE that is NEGATIVELY CHARGED. IONIC BONDS typically form between METALLIC and NONMETALLIC atoms. The METALLIC ATOMS release their VALENCE ELECTRONS to become CATIONS, and the NONMETALLIC ATOMS accept ELECTRONS to become ANIONS. A METALLIC BOND is a BOND that occurs in materials whose atoms has βπ β electrons as their HIGHEST ENERGY ELECTRONS. In a METALLIC BOND, the VALENCE ELECTRONS form a NEGATIVELY CHARGED cloud, and leverage the FORCE of ATTRACTION between the VALENE ELECTRONS and the METAL IONS. In forming METALLIC BONDS, it is the SHARING of many DETACHED ELECTRONS between POSITIVE IONS, where the ELECTRONS act as a GLUE giving the SUSTANCE a definite STRUCTURE.
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CONCEPT EXAMPLE: The atomic weight of nitrogen is most close to: A. 9.0122 B. 20.179 C. 14.007 D. 22.990
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SOLUTION: The PERIODIC TABLE OF ELEMENTS can be referenced under the SUBJECT of CHEMISTRY on page 55 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In this problem we are looking to solve for the ATOMIC WEIGHT of NITROGEN. Looking at the PERIODIC TABLE OF ELEMENTS in the reference handbook, we see that we are given the ATOMIC NUMBER, SYMBOL, and ATOMIC WEIGHT for every ELEMENT on the TABLE. Therefore, the first step in this PROBLEM is to simply IDENTIFY the SYMBOL for NITROGEN in the PERIODIC TABLE. In the Reference Handbook, we are not EXPLICITLY TOLD the corresponding SYMBOLS for each ELEMENT, so we must be able to IDENTIFY the SYMBOL of each ELEMENT from MEMORIZATION or using CONTEXT CLUES in the PERIODIC TABLE. When in doubt try to MATCH up the SYMBOL for the ELEMENT by looking at the SPELLING of the ELEMENT. This will NOT WORK for all ELEMENTS, but can help you to ELIMINATE answer choices and REVERSE ENGINEER the PERIODIC TABLE.
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Looking at the PERIODIC TABLE, we see that in COLUMN V, there is the SYMBOL βNβ, which represents NITROGEN.
Referencing the information for NITROGEN in the periodic table, we find the associated ATOMIC WEIGHT for NITROGEN is given as 14.007.
Therefore, the correct answer choice is C. ππ. πππ
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CONCEPT INTRO: CHEMISTRY is the study of MATTER and the CHANGES it undergoes with respect to PHYSICAL PROPERTIES, COMPOSITION, and CHEMICAL STRUCTURE. A PHASE is a HOMOGENEOUS STATE of a SUBSTANCE with UNIFORM physical and chemical characteristics. There are THREE possible STATES or PHASES of MATTER that exist (GAS, LIQUID, or SOLID), depending on the TEMPERATURE, PRESSURE, and COMPOSITION of the SUBSTANCE. A PHASE CHANGE is the change of a SUBSTANCEβS MATTER from one PHYSICAL STATE to another due to conditions such as PRESSURE, VOLUME, or TEMPERATURE. A GAS has NO definite SHAPE or VOLUME, and is classified as being easily COMPRESSIBLE. Made with
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A LIQUID has CONSTANT VOLUME and is classified as having NO definite SHAPE, being slightly COMPRESSIBLE. A SOLID has DEFINITE VOLUME and SHAPE, and is classified as being RIGID and DIFFICULT to COMPRESS. A SUBSTANCE is a FORM of MATTER that has a definite COMPOSITION and distinct PROPERTIES, such that a SUBSTANCE is classified as either an ELEMENT or a COMPOUND. An ISOTROPIC SUBSTANCE is a SUBSTANCE that has the SAME PHYSICAL PROPERTIES in ALL DIRECTIONS. All MATTER is CLASSIFIED as either a MIXTURE or a PURE SUBSTANCE. A MIXTURE is a combination of TWO or more SUBSTANCES are PHYSICALLY BONDED, in which the substances retain their distinct identities, and is classified as either HOMOGENEOUS or HETEROGENEOUS. Any MIXTURE can be CREATED and then SEPARATED by PHYSICAL MEANTS into individual PURE SUBSTANCES without changing the PROPERTIES or IDENTITY of the COMPONENTS. A HOMOGENEOUS MIXTURE is a MIXTURE that has a UNIFORM or HOMOGENEOUS composition throughout the mixture, with the COMPOSITION remaining CONSTANT.
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A HETEROGENEOUS MIXTURE is a MIXTURE that a NON-UNIFORM or HETEROGENEOUS composition throughout the mixture, with the COMPOSITION varying. For example, in a MIXTURE of SUGAR WATER, the SUGAR can be removed from WATER solution by heating the solution and EVAPORATING the WATER from the solution. Thus the SUGAR and WATER are PHYSICALLY SEPARATED. A PURE SUBSTANCE is a SUBSTANCE that cannot be SEPARATED into COMPONENTS by PHYSICAL MEANS, and retains its CHEMICAL COMPOSITION through all THREE PHRASES. An ELEMENT is a PURE SUBSTANCE that is composed of only ONE type of ATOM that has identical CHEMICAL PROPERTIES, having the same SIZE, MASS, and CHEMICAL MAKEUP. A COMPOUND is a PURE SUBSTANCE comprised of ATOMS from two or more ELEMENTS are CHEMICALLY COMBINED in FIXED RATIOS. An example of a COMPOUND is CARBON DIOXIDE which is always COMPOSED of MOLECULES with TWO ATOMS of OXYGEN for every ONE ATOM of CARBON. In any COMPOUND, the RATIO of the numbers of ATOMS of any two of the ELEMENTS present is either an integer or a simple fraction.
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Unlike MIXTURES, COMPOUNDS can be separated into their BASE ELEMENTS by CHEMICAL MEANS into their PURE COMPONENTS. ATOMIC STRUCTURE: The TOPIC of ELECTRON CONFIGURATIONS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. ATOMS are the BUILDING BLOCKS of matter, and define the PROPERTIES and BEHAVIORS of an ELEMENTS. Atoms of one ELEMENT are IDENTICAL in MASS and other PROPERTIES, and cannot be CONVERTED into atoms of another ELEMENT. MATTER is composed of ATOMS that are ELECTRICALLY CHARGED in one of two ways, either being POSITIVELY CHARGED (+) or NEGATIVELY CHARGED (-). ELECTROMAGNETIC FORCES or COULOMBIC FORCES are forces that cause atoms to be ATTRACTED to other ATOMS as a result of ELECTRIC POLARITIES and ELECTROSTATIC INTERACTIONS. ELECTROSTATIC FORCES can provide an ATTRACTIVE FORCE or a REPULSIVE FORCE based on the ELECTRICAL CHARGE on each of the ATOMS.
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An ATOM is composed of a central core NUCLEUS that is surrounded by NEGATIVELY CHARGED ELECTRONS (π β ). Within the NUCLEUS, an ATOM contains POSITIVE CHARGED PROTONS and NEUTRALLY CHARGED NEUTRONS. An ELECTRON is a NEGATIVELY charged particle, the magnitude of whose CHARGE is EQUAL to that of the PROTON. A PROTON is a POSITIVELY charged particle, the magnitude of whose CHARGE is EQUAL to that of the ELECTRON. A NEUTRON is an ELECTRICALLY NEUTRAL particle, neither positively nor negatively charged, whose MASS can be taken EQUAL to that of the PROTON. An ATOM has no charge and is considered NEUTRAL, such that it contains an EQUAL number of PROTONS and ELECTRONS, which provide an EQUIVALENT number of POSITIVE and NEGATIVE charges resulting in a net ELECTRICAL CHARGE of ZERO. CHEMICAL REACTIONS involve either the TRANSFER or the SHARING of ELECTRONS between ATOMS. Therefore, we can say that the CHEMICAL REACTIVITY of an atom is DEPENDENT upon the number of ELECTRONS and PROTONS, and is INDEPENDENT of the number of NEUTRONS.
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The BOHR MODEL uses the terms ENERGY LEVELS, ORBITALS, or SHELLS to describe the SEPARATION of differing ENERGY LEVELS of ELECTRONS around the NUCLEUS of the ATOM. The TOPIC of the PHOTOELECTRIC EFFECT can be referenced under the SUBJECT of MATERIALS SCIENCE on page 60 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. A PHOTON is the AMOUNT of ENERGY released if an ELECTRON moves from a HIGHER ENERGY SHELL to the next LOWER ENERGY SHELL. The PHOTOELECTRIC EFFECT is an occurrence where ELECTRONS are EMITTED from MATTER as RESULT of their ABSORPTION of ENERGY from ELECTROMAGNETIC RADIATION.
The ENERGY LEVEL an electron normally occupies is called its GROUND STATE. Made with
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However, it can move to a HIGHER-ENERGY, LESS-STABLE orbital, or SHELL, by ABSORBING ENERGY. The EXCITED STATE is the HIGHER ENERGY and LESS STABLE orbital of the ATOM, AND enables EASY removal or transfer of an ELECTRON from ONE ENERGY LEVEL to another. After an ELECTRON is done being EXCITED, the ELECTRON can return to its original GROUND STATE by RELEASING the ENERGY it has ABSORBED. This happens because of the effect of ELECTRON REPULSION also known as ELECTRON SHIELDING, which is a result of the ELECTRON being attracted to the POSITIVE CHARGE of the NUCLEUS. ELECTRONS that are on the OUTERMOST ENERGY LEVEL are commonly referred to as VALENCE ELECTRONS. One of the properties that ELEMENTS within a GROUP share is the tendency to gain or lose a specific number of VALENCE ELECTRONS, which is referred to as the VALENCE or VALENCE STATE. For some elements, the number of electrons that can be naturally gained or lost is nonspecific and can change depending on the circumstances. These elements are said to have a MULTI-VALENCE STATE.
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ELECTRON CONFIGURATIONS: The TOPIC of ELECTRON CONFIGURATIONS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. In chemistry, we often like to know the LOCATION of an ELECTRON relative to the ENERGY LEVEL or ORBITAL of the ATOMβS NUCLEUS. A useful way of doing this is to determine the ELECTRON CONFIGURATION of an ATOM, which will define the ADDRESS of each ELECTRON in the ATOM. The ELECTRON CONFIGURATION is the STANDARD NOTATION, also known as ORBITAL NOTATION, used to DESCRIBE the ELECTRONIC STRUCTURE of an ATOM. The ELECTRON CONFIGURATION of an ELEMENT aids in PREDICTING how ATOMS will join together to form CHEMICAL BONDS and how ELECTRONS define the CHARACTERISTICS of an ELEMENT. The PAULI EXCLUSION PRINCIPLE states that ELECTRONS occupy ENERGY LEVELS in such a way that no more than TWO ELECTRONS can occupy the same ORBITAL, and both ELECTRONS must have OPPOSITE MANGETIC SPINS relative to each other.
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Within the ORBITAL or ENERGY LEVEL designated by each value of βπβ, there is further QUANTIZATION of ENERGY, indicated by the letters βπ , π, π, πππ πβ in ORDER of INCREASING ENERGY.
Electron Configuration of Elements Shell
π
π
Element
s
s
p
Hydrogen
1
Helium
2
Carbon
2
2
2
Nitrogen
2
2
3
Oxygen
2
2
4
Sodium
2
2
6
1
Aluminum
2
2
6
2
1
Chlorine
2
2
6
2
5
Iron
2
2
6
2
Copper
2
2
6
Cadmium
2
2
Xenon
2
Gold
2
π s
p
π d
s
6
6
2
2
6
10
1
6
2
6
10
2
6
2
6
2
6
2
6
π
p
d
f
2
6
10
2
10
2
6
10
2
6
10
2
6
10
2
6
14
s
p
d
f
10
Each numbered ROW of the PERIODIC TABLE corresponds to a different principal ENERGY LEVEL, with higher numbers indicating higher energy. In each electron configuration, the magnitude of βπβ is given first, followed by the designation of βπ ,β and, if appropriate, of βπβ and βπβ. Made with
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The NUMBER of ELECTRONS within each orbital designation is shown as a SUPERSCRIPT. The sum of the SUPERSCRIPTS is, therefore, the number of ELECTRONS in the ATOMS. PERIODIC TABLE: The REFERENCE for the PERIODIC TABLE can be referenced under the SUBJECT of CHEMISTRY on page 55 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. The PERIODIC TABLE is a TABULAR ARRANGEMENT of the CHEMICAL ELEMENTS the associated ATOMIC NUMBER, SYMBOL, and ATOMIC WEIGHT of each ELEMENT. The CHEMICAL IDENTITY of an ATOM can be determined from EVALUATING the ATOMIC NUMBER and ATOMIC WEIGHT, and cross-referencing those values with the PERIODIC TABLE.
The ATOMIC NUMBER of an ELEMENT is the NUMBER of PROTONS in the NUCLEUS of each atom of an ELEMENT. Made with
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The ATOMIC NUMBER is a POSITIVE INTEGER beginning at 1 for Hydrogen and increases, by 1, for each subsequent atom. Thus, the ATOMIC NUMBERS of Hydrogen, Helium, Sodium, Aluminum, and Oxygen are, respectively, 1, 2, 11, 13, and 8. In a NEUTRAL ATOM, the number of PROTONS is EQUAL to the number of ELECTRONS, so the ATOMIC NUMBER also indicates the number of ELECTRONS present in the ELEMENT. The CHEMICAL SYMBOL is a one- or two- letter ABBREVIATION assigned to each ELEMENT based on the NAME of the ELEMENT. Some CHEMICAL SYMBOLS are based on the LATIN or GERMAN name of the element, so donβt always assume with the first one- or two- letters. The REFERENCE for the PROPERTIES OF METALS can be referenced under the SUBJECT of MATERIALS SCIENCE on page 61 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. For the purposes of the FE Exam, it is not worth your time to MEMORIZE the SYMBOL for every ELEMENT. Instead I would recommend you become FAMILIAR with the TABLE of the PROPERTIES of METALS in the REFERENCE HANDBOOK, which lists the METAL NAME and CHEMICAL SYMBOL for a variety of ELEMENTS.
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On this TABLE, you will find the METAL NAME and CHEMICAL SYMBOL, which you can use to help ELIMINATE answer choices within PROBLEMS.
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The ATOMIC WEIGHT, also known as the ATOMIC MASS NUMBER is the TOTAL NUMBER of NEUTRONS and PROTONS present in the NUCLEUS of an atom of an element, and is calculated as: πππ π ππ’ππππ = π΄π‘ππππ ππ’ππππ + πππ’π‘ππππ = ππππ‘πππ + πππ’π‘ππππ ATOMIC WEIGHT in CHEMISTRY represents the AVERAGE WEIGHT of all naturally occurring ISOTOPES of an ELEMENT and is given in units of ATOMIC MASS UNITS (amu) or GRAMS (g), where one ATOMIC MASS UNIT (AMU) represents: 1 πππ’ = 1.66 Γ 10β27 ππ 1
By definition, an ATOMIC MASS UNIT (amu) is 12 of the MASS of the CARBON-12 ISOTOPE that has SIX PROTONS and SIX NEUTRONS, C12 . ISOTOPES are ATOMS of the same ELEMENT with the SAME NUMBER of PROTONS, but a different ATOMIC MASS NUMBER resulting from a DIFFERENCE in the varying number of NEUTRONS. ATOMS of the DIFFERENT ISOTOPES of an ELEMENT are DISTINGUISHED by using the MASS NUMBER as a SUPERSCRIPT to the left of the ELEMENT SYMBOL. For example, 14 N and 15 N are both ISOTOPES of NITROGEN because they have the same PROTON NUMBER, but have differing MASS NUMBERS representing the SUM of the PROTONS and NEUTRONS in each particular ISOTOPE.
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The FORMULA to CALCULATE AVERAGE ATOMIC MASS is not provided in the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. We must memorize this formula and understand its application independent of the NCEES Supplied Reference Handbook. To calculate the AVERAGE ATOMIC MASS from the known ISOTOPES of a given element, we use the equation for WEIGHTED AVERAGE based on the ABUNDANCE of each ISOTOPE: π΄π£πππππ π΄π‘ππππ πππ π = β(ππΌ Γ π΄πΌ )π Where: β’ ππΌ represents the MASS of the ISOTOPE β’ π΄πΌ represents the ABUNDANCE of the ISOTOPE, and WEIGHT of the AVERAGE β’ π is the NUMBER of ISOTOPES Each ISOTOPE has its own ABUNDANCE in NATURE, where the PERCENT ABUNDANCES of all the ISOTOPES of an ELEMENT have to equal 100%. ATOMIC BONDING: The TOPIC of ATOMIC BONDING can be referenced under the SUBJECT of MATERIALS SCIENCE on page 60 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. The BEHAVIOR of a SUBSTANCE is defined by the TYPE of CHEMICAL BONDS that define the STRUCTURE of the ATOMS comprising the SUBSTANCE. Made with
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A MOLECULE represents the SMALLEST PARTICLE of a particular ELEMENT or COMPOUND that can EXIST and RETAIN the CHEMICAL properties. When two elements interact, it is the OUTER ELECTRONS known as the VALENCE ELECTRONS, that are involved in the formation of CHEMICAL BONDS. MOLECULES are combinations of ATOMS bonded TOGETHER by IONIC and COVALENT BONDS. In forming COVALENT BONDS, elements are looking to make their OUTER SHELL of ELECTRONS totally full by SHARING valence electrons between ATOMS. COVALENT BONDS are the STRONGEST ATTRACTIVE FORCES typically FORMED between ATOMS with half-filled ORBITALS, as well as between NON-METALS, or between NON-METALS and METALLOIDS. The NUMBER of ELECTRONS shared is usually enough to fill the outermost VALENCE SHELLS and thus bring both atoms to their NOBLE GAS CONFIGURATION.
IONIC BONDING is based on the ELECTROSTATIC or COULOMBIC ATTRACTION between opposite ELECTRICALLY CHARGED ions, and the TRANSFER of ONE or more ELECTRONS from one ATOM to another. IONS are CHARGED ATOMS that LOST or GAINED ELECTRONS, resulting in a net ELECTRICAL charge NOT EQUAL to ZERO. Made with
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In forming IONIC BONDS, elements are looking to make their OUTER SHELL of ELECTRONS either totally FULL, or totally EMPTY, by either LOSING or GAINING valence electrons. A CATION is a POSITIVE ION that has ACCEPTED extra ELECTRONS, resulting in an ATOMIC STRUCTURE that is POSITIVELY CHARGED. An ANION is a NEGATIVE ION that has DONATED extra ELECTRONS, resulting in an ATOMIC STRUCTURE that is NEGATIVELY CHARGED. IONIC BONDS typically form between METALLIC and NONMETALLIC atoms. The METALLIC ATOMS release their VALENCE ELECTRONS to become CATIONS, and the NONMETALLIC ATOMS accept ELECTRONS to become ANIONS. A METALLIC BOND is a BOND that occurs in materials whose atoms has βπ β electrons as their HIGHEST ENERGY ELECTRONS. In a METALLIC BOND, the VALENCE ELECTRONS form a NEGATIVELY CHARGED cloud, and leverage the FORCE of ATTRACTION between the VALENE ELECTRONS and the METAL IONS. In forming METALLIC BONDS, it is the SHARING of many DETACHED ELECTRONS between POSITIVE IONS, where the ELECTRONS act as a GLUE giving the SUSTANCE a definite STRUCTURE.
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CONCEPT EXAMPLE: The atomic weight of nitrogen is most close to: A. 9.0122 B. 20.179 C. 14.007 D. 22.990
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SOLUTION: The PERIODIC TABLE OF ELEMENTS can be referenced under the SUBJECT of CHEMISTRY on page 55 of the NCEES Supplied Reference Handbook, Version 9.4 for Computer Based Testing. In this problem we are looking to solve for the ATOMIC WEIGHT of NITROGEN. Looking at the PERIODIC TABLE OF ELEMENTS in the reference handbook, we see that we are given the ATOMIC NUMBER, SYMBOL, and ATOMIC WEIGHT for every ELEMENT on the TABLE. Therefore, the first step in this PROBLEM is to simply IDENTIFY the SYMBOL for NITROGEN in the PERIODIC TABLE. In the Reference Handbook, we are not EXPLICITLY TOLD the corresponding SYMBOLS for each ELEMENT, so we must be able to IDENTIFY the SYMBOL of each ELEMENT from MEMORIZATION or using CONTEXT CLUES in the PERIODIC TABLE. When in doubt try to MATCH up the SYMBOL for the ELEMENT by looking at the SPELLING of the ELEMENT. This will NOT WORK for all ELEMENTS, but can help you to ELIMINATE answer choices and REVERSE ENGINEER the PERIODIC TABLE.
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Looking at the PERIODIC TABLE, we see that in COLUMN V, there is the SYMBOL βNβ, which represents NITROGEN.
Referencing the information for NITROGEN in the periodic table, we find the associated ATOMIC WEIGHT for NITROGEN is given as 14.007.
Therefore, the correct answer choice is C. ππ. πππ
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