Electrons
Electrons How many electrons fit in each shell around an atom? The maximum number of electrons that can occupy a specific energy level can be found using the following formula: Electron Capacity = 2n2 The variable n represents the Principal Quantum Number, the number of the energy level in question.
Keep in mind that an energy level need not be completely filled before electrons begin to fill the next level. You should always use the Periodic Table of Elements to check an element's electron configuration table if you need to know exactly how many electrons are in each level. How are electrons placed in shells around the nucleus? Electrons tend to arrange themselves around nuclei so that they have the lowest possible energy. They would all like to get into the lowest energy level, sometimes called the K-shell, but are prevented from doing so by some rules that pop up in quantum mechanics. You can see how electrons are arranged in a particular atom by taking a look at our Periodic Table of Elements. Let's use oxygen as an example. Oxygen's electron configuration is:
This means that the first energy level (the K-shell) contains 2 electrons, both in sub-shell s, and that the second energy level (the L-shell) contains 6 electrons, 2 in sub-shell s and 4 in sub-shell p. As more electrons are added, higher energy levels with more sub-shells become filled. Here is a list of the first few energy levels, their sub-shells, and the maximum number of electrons that they can contain:
What is an electron configuration table? An electron configuration table is a type of code that describes how many electrons are in each energy level of an atom and how the electrons are arranged within each energy level. It packs a lot of information into a little space and it takes a little practice to read: For example, this is the electron configuration table for gold
What do all those numbers and letters mean? Each row of an electron configuration table is sort of like a sentence. Each 'sentence' is made up of smaller 'words'. Each 'word' follows this format: The first number is the energy level. An atom of gold contains 6 energy levels. The lowercase letter is the sub-shell. Sub-shells are named s, p, d and f. Number of available sub-shells increases as the energy level increases. Example, the first energy level only contains an s sub-shell while the second energy level contains both an s sub-shell and a p sub-shell. The number in superscript is the number of electrons in a sub-shell. Each sub-shell can hold only a certain number of electrons. The s sub-shell can hold no more than 2 electrons, the p subshell can hold 6, the d sub-shell can hold 10 and the f sub-shell can hold as many as 14. How can I use the electron configuration table to tell me... How many energy levels does an atom have? Since the electron configuration table lists each energy level by row, you can tell how many energy levels there are by seeing how many rows there are. An atom of gold contains six energy levels, as shown below:
How many electrons are in each energy level? The total number of electrons in an energy level is the sum of the electrons in each sub-shell of that energy level. Add the numbers in superscript together to find the number of electrons in an energy level. Number of electrons in each energy level in an atom of gold is shown below:
How many electrons are in an atom's outer energy level? This is just a combination of the previous two examples. Use the electron configuration to find that atom's highest energy level and then add up the numbers in superscript to find the number of electrons that are in it. There is one electron in the outer energy level of an atom of gold, as shown below:
Energy levels, sublevels, & orbitals http://www.youtube.com/watch?v=kXfaQEkWXFM
Orbital diagrams http://www.youtube.com/watch?v=rFErf7esP0w
Electron configuration http://www.youtube.com/watch?v=jbxQWye9yD4
Noble gas configuration https://www.youtube.com/watch?v=MPXbvzj0-yI
Electron configuration with ions https://www.youtube.com/watch?v=mBLoa1shbGU
Ground State & Excited State Conversions - October 28 https://www.youtube.com/watch?v=PphXv4GwGbQ
Drawing & Writing Electron Configurations
http://www.youtube.com/watch?v=J7Hlqk0_ykU METHOD 1: ASSIGNING ELECTRONS USING A PERIODIC TABLE 1. Find your atom's atomic number. Each atom has a specific number of electrons associated with it. Locate your atom's chemical symbol on the periodic table. The atomic number is a positive integer beginning at 1 (for hydrogen) and increasing by 1 for each subsequent atom. The atom's atomic number is the number of protons of the atom - thus, it is also the number of electrons in an atom with zero charge. 2. Determine the charge of the atom. Uncharged atoms will have exactly the number of electrons as is represented on the periodic table. However, charged atoms will have a higher or lower number of electrons based on the magnitude of their charge. If you're working with a charged atom, add or subtract electrons accordingly: add one electron for each negative charge and subtract one for each positive charge. For instance, a sodium atom with a -1 charge would have an extra electron in addition to its basic atomic number of 11. So, the sodium atom would have 12 electrons in total. 3. Memorize the basic list of orbitals. As an atom gains electrons, they fill different orbitals sets according to a specific order. Each set of orbitals, when full, contains an even number of electrons. The orbital sets are: The s orbital set (any number in the electron configuration followed by an "s") contains a single orbital, and by Pauli's Exclusion Principle, a single orbital can hold a maximum of 2 electrons, so each s orbital set can hold 2 electrons. The p orbital set contains 3 orbitals, and thus can hold a total of 6 electrons. The d orbital set contains 5 orbitals, so it can hold 10 electrons. The f orbital set contains 7 orbitals, so it can hold 14 electrons.
4. Understand electron configuration notation. Electron configurations are written so as to clearly display the number of electrons in the atom as well as the number of electrons in each orbital. Each orbital is written in sequence, with the number of electrons in each orbital written in superscript to the right of the orbital name. The final electron configuration is a single string of orbital names and superscripts. For example, here is a simple electron configuration: 1s2 2s2 2p6. This configuration shows that there are two electrons in the 1s orbital set, two electrons in the 2s orbital set, and six electrons in the 2p orbital set. 2 + 2 + 6 = 10 electrons total. This electron configuration is for an uncharged neon atom (neon's atomic number is 10.) 5. Memorize the order of the orbitals. Note that orbital sets are numbered by electron shell, but ordered in terms of energy. For instance, a filled 4s2 is lower energy (or less potentially volatile) than a partially-filled or filled 3d10, so the 4s shell is listed first. Once you know the order of orbitals, you can simply fill them according to the number of electrons in the atom. The order for filling orbitals is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s. An electron configuration for an atom with every orbital completely filled would be written: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s25f14 6d107p68s2 Note that the above list, if all the shells were filled, would be the electron configuration for Uuo (ununoctium), 118, the highest-numbered atom on the periodic table - so this electron configuration contains every currently known electron shell for a neutrally charged atom. 6. Fill in the orbitals according to the number of electrons in your atom. For instance, if we want to write an electron configuration for an uncharged calcium atom, we'll begin by finding its atomic number on the periodic table. Its atomic number is 20, so we'll write a configuration for an atom with 20 electrons according to the order above. Fill up orbitals according to the order above until you reach twenty total electrons. The 1s orbital gets two electrons, the 2s gets two, the 2p gets six, the 3s gets two, the 3p gets 6, and the 4s gets 2 (2 + 2 + 6 +2 +6 + 2 = 20.) Thus, the electron configuration for calcium is: 1s2 2s2 2p6 3s2 3p6 4s2. Note: Energy level changes as you go up. For example, when you are about to go up to the 4th energy level, it becomes 4s first, then 3d. After the fourth energy level, you'll move onto the 5th where it follows the order once again. This only happens after the 3rd energy level. 7. Use the periodic table as a visual shortcut. You may have already noticed that the shape of the periodic table corresponds to the order of orbital sets in electron configurations. For example, atoms in the second column from the left always end in "s2", atoms at the far right of the skinny middle portion always end in "d10," etc. Use the periodic table as a visual guide to write configurations - the order that you add
electrons to orbitals corresponds to your position in the table. See below: Specifically, the two leftmost columns represent atoms whose electron configurations end in s orbitals, the right block of the table represents atoms whose configurations end in p orbitals, the middle portion, atoms that end in d orbital, and the bottom portion, atoms that end in f orbitals. For example, when writing an electron configuration for Chlorine, think: "This atom is in third row (or "period") of the periodic table. It's also in the fifth column of the periodic table's p orbital block. Thus, its electron configuration will end ...3p 5 Caution - the d and f orbital regions of the table correspond to energy levels that are different than the period they're located in. For instance, the first row of the d orbital block corresponds to the 3d orbital even though it's in period 4, while the first row of the f orbital corresponds to the 4f orbital even though it's in period 6. 8. Learn shorthand for writing long electron configurations. The atoms along the right edge of the periodic table are called noble gases. These elements are very chemically stable. To shorten the process of writing a long electron configuration, simply write the chemical symbol of the nearest chemical gas with less electrons than your atom in brackets, then continue with the electron configuration for the following orbital sets. See below: To understand this concept, it's useful to write an example configuration. Write a configuration for Zinc (atomic number 30) using noble gas shorthand. Zinc's full electron configuration is: 1s2 2s2 2p6 3s2 3p6 4s2 3d10. However, notice that 1s2 2s2 2p6 3s2 3p6 is the configuration for Argon, a noble gas. Just replace this portion of Zinc's electron notation with Argon's chemical symbol in brackets ([Ar].) So, Zinc's electron configuration written in shorthand is [Ar]4s2 3d10. 9.
Electronic Configurations http://legacy.chemgym.net/as_a2/topics/electronic_configurations/index.html
MAIN energy level "1" has only 1 sublevel, the "s" orbital sublevel. MAIN energy level "2" has two sublevels, both the "s" and "p" sublevels. MAIN energy level "3" has three sublevels, "s", "p" and "d." The pattern continues with MAIN energy levels "4, 5, 6 and 7," but the higher sublevels of "5, 6 and 7" (those shown in parentheses above) do not appear in the standard electron configuration pattern, because there are only 117 known elements, so after 117, we don't have any more electrons to put into the higher orbitals. Each succeeding MAIN energy level has more orbital sublevels because as we move out from the nucleus of the atom, there is more room for more electrons which can have the same MAIN amount of energy but have different orientations in space and different angular momenta.
Now look at the small black raised numbers. The small raised numbers shown above in black are called "superscripts." Superscripts represent the maximum numbers of electrons each orbital sublevel can hold. An orbital sublevel may hold LESS electrons than its maximum, but it can never hold MORE.
http://education.jlab.org/qa/electron_config.html http://preparatorychemistry.com/Bishop_Chemistry_First.htm http://preparatorychemistry.com/Bishop_comp_electron_config_Flash1.htm http://electronconfiguration.info/
Keep in mind that an energy level need not be completely filled before electrons begin to fill the next level. You should always use the Periodic Table of Elements to check an element's electron configuration table if you need to know exactly how many electrons are in each level. How are electrons placed in shells around the nucleus? Electrons tend to arrange themselves around nuclei so that they have the lowest possible energy. They would all like to get into the lowest energy level, sometimes called the K-shell, but are prevented from doing so by some rules that pop up in quantum mechanics. You can see how electrons are arranged in a particular atom by taking a look at our Periodic Table of Elements. Let's use oxygen as an example. Oxygen's electron configuration is:
This means that the first energy level (the K-shell) contains 2 electrons, both in sub-shell s, and that the second energy level (the L-shell) contains 6 electrons, 2 in sub-shell s and 4 in sub-shell p. As more electrons are added, higher energy levels with more sub-shells become filled. Here is a list of the first few energy levels, their sub-shells, and the maximum number of electrons that they can contain:
What is an electron configuration table? An electron configuration table is a type of code that describes how many electrons are in each energy level of an atom and how the electrons are arranged within each energy level. It packs a lot of information into a little space and it takes a little practice to read: For example, this is the electron configuration table for gold
What do all those numbers and letters mean? Each row of an electron configuration table is sort of like a sentence. Each 'sentence' is made up of smaller 'words'. Each 'word' follows this format: The first number is the energy level. An atom of gold contains 6 energy levels. The lowercase letter is the sub-shell. Sub-shells are named s, p, d and f. Number of available sub-shells increases as the energy level increases. Example, the first energy level only contains an s sub-shell while the second energy level contains both an s sub-shell and a p sub-shell. The number in superscript is the number of electrons in a sub-shell. Each sub-shell can hold only a certain number of electrons. The s sub-shell can hold no more than 2 electrons, the p subshell can hold 6, the d sub-shell can hold 10 and the f sub-shell can hold as many as 14. How can I use the electron configuration table to tell me... How many energy levels does an atom have? Since the electron configuration table lists each energy level by row, you can tell how many energy levels there are by seeing how many rows there are. An atom of gold contains six energy levels, as shown below:
How many electrons are in each energy level? The total number of electrons in an energy level is the sum of the electrons in each sub-shell of that energy level. Add the numbers in superscript together to find the number of electrons in an energy level. Number of electrons in each energy level in an atom of gold is shown below:
How many electrons are in an atom's outer energy level? This is just a combination of the previous two examples. Use the electron configuration to find that atom's highest energy level and then add up the numbers in superscript to find the number of electrons that are in it. There is one electron in the outer energy level of an atom of gold, as shown below:
Energy levels, sublevels, & orbitals http://www.youtube.com/watch?v=kXfaQEkWXFM
Orbital diagrams http://www.youtube.com/watch?v=rFErf7esP0w
Electron configuration http://www.youtube.com/watch?v=jbxQWye9yD4
Noble gas configuration https://www.youtube.com/watch?v=MPXbvzj0-yI
Electron configuration with ions https://www.youtube.com/watch?v=mBLoa1shbGU
Ground State & Excited State Conversions - October 28 https://www.youtube.com/watch?v=PphXv4GwGbQ
Drawing & Writing Electron Configurations
http://www.youtube.com/watch?v=J7Hlqk0_ykU METHOD 1: ASSIGNING ELECTRONS USING A PERIODIC TABLE 1. Find your atom's atomic number. Each atom has a specific number of electrons associated with it. Locate your atom's chemical symbol on the periodic table. The atomic number is a positive integer beginning at 1 (for hydrogen) and increasing by 1 for each subsequent atom. The atom's atomic number is the number of protons of the atom - thus, it is also the number of electrons in an atom with zero charge. 2. Determine the charge of the atom. Uncharged atoms will have exactly the number of electrons as is represented on the periodic table. However, charged atoms will have a higher or lower number of electrons based on the magnitude of their charge. If you're working with a charged atom, add or subtract electrons accordingly: add one electron for each negative charge and subtract one for each positive charge. For instance, a sodium atom with a -1 charge would have an extra electron in addition to its basic atomic number of 11. So, the sodium atom would have 12 electrons in total. 3. Memorize the basic list of orbitals. As an atom gains electrons, they fill different orbitals sets according to a specific order. Each set of orbitals, when full, contains an even number of electrons. The orbital sets are: The s orbital set (any number in the electron configuration followed by an "s") contains a single orbital, and by Pauli's Exclusion Principle, a single orbital can hold a maximum of 2 electrons, so each s orbital set can hold 2 electrons. The p orbital set contains 3 orbitals, and thus can hold a total of 6 electrons. The d orbital set contains 5 orbitals, so it can hold 10 electrons. The f orbital set contains 7 orbitals, so it can hold 14 electrons.
4. Understand electron configuration notation. Electron configurations are written so as to clearly display the number of electrons in the atom as well as the number of electrons in each orbital. Each orbital is written in sequence, with the number of electrons in each orbital written in superscript to the right of the orbital name. The final electron configuration is a single string of orbital names and superscripts. For example, here is a simple electron configuration: 1s2 2s2 2p6. This configuration shows that there are two electrons in the 1s orbital set, two electrons in the 2s orbital set, and six electrons in the 2p orbital set. 2 + 2 + 6 = 10 electrons total. This electron configuration is for an uncharged neon atom (neon's atomic number is 10.) 5. Memorize the order of the orbitals. Note that orbital sets are numbered by electron shell, but ordered in terms of energy. For instance, a filled 4s2 is lower energy (or less potentially volatile) than a partially-filled or filled 3d10, so the 4s shell is listed first. Once you know the order of orbitals, you can simply fill them according to the number of electrons in the atom. The order for filling orbitals is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s. An electron configuration for an atom with every orbital completely filled would be written: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s25f14 6d107p68s2 Note that the above list, if all the shells were filled, would be the electron configuration for Uuo (ununoctium), 118, the highest-numbered atom on the periodic table - so this electron configuration contains every currently known electron shell for a neutrally charged atom. 6. Fill in the orbitals according to the number of electrons in your atom. For instance, if we want to write an electron configuration for an uncharged calcium atom, we'll begin by finding its atomic number on the periodic table. Its atomic number is 20, so we'll write a configuration for an atom with 20 electrons according to the order above. Fill up orbitals according to the order above until you reach twenty total electrons. The 1s orbital gets two electrons, the 2s gets two, the 2p gets six, the 3s gets two, the 3p gets 6, and the 4s gets 2 (2 + 2 + 6 +2 +6 + 2 = 20.) Thus, the electron configuration for calcium is: 1s2 2s2 2p6 3s2 3p6 4s2. Note: Energy level changes as you go up. For example, when you are about to go up to the 4th energy level, it becomes 4s first, then 3d. After the fourth energy level, you'll move onto the 5th where it follows the order once again. This only happens after the 3rd energy level. 7. Use the periodic table as a visual shortcut. You may have already noticed that the shape of the periodic table corresponds to the order of orbital sets in electron configurations. For example, atoms in the second column from the left always end in "s2", atoms at the far right of the skinny middle portion always end in "d10," etc. Use the periodic table as a visual guide to write configurations - the order that you add
electrons to orbitals corresponds to your position in the table. See below: Specifically, the two leftmost columns represent atoms whose electron configurations end in s orbitals, the right block of the table represents atoms whose configurations end in p orbitals, the middle portion, atoms that end in d orbital, and the bottom portion, atoms that end in f orbitals. For example, when writing an electron configuration for Chlorine, think: "This atom is in third row (or "period") of the periodic table. It's also in the fifth column of the periodic table's p orbital block. Thus, its electron configuration will end ...3p 5 Caution - the d and f orbital regions of the table correspond to energy levels that are different than the period they're located in. For instance, the first row of the d orbital block corresponds to the 3d orbital even though it's in period 4, while the first row of the f orbital corresponds to the 4f orbital even though it's in period 6. 8. Learn shorthand for writing long electron configurations. The atoms along the right edge of the periodic table are called noble gases. These elements are very chemically stable. To shorten the process of writing a long electron configuration, simply write the chemical symbol of the nearest chemical gas with less electrons than your atom in brackets, then continue with the electron configuration for the following orbital sets. See below: To understand this concept, it's useful to write an example configuration. Write a configuration for Zinc (atomic number 30) using noble gas shorthand. Zinc's full electron configuration is: 1s2 2s2 2p6 3s2 3p6 4s2 3d10. However, notice that 1s2 2s2 2p6 3s2 3p6 is the configuration for Argon, a noble gas. Just replace this portion of Zinc's electron notation with Argon's chemical symbol in brackets ([Ar].) So, Zinc's electron configuration written in shorthand is [Ar]4s2 3d10. 9.
Electronic Configurations http://legacy.chemgym.net/as_a2/topics/electronic_configurations/index.html
MAIN energy level "1" has only 1 sublevel, the "s" orbital sublevel. MAIN energy level "2" has two sublevels, both the "s" and "p" sublevels. MAIN energy level "3" has three sublevels, "s", "p" and "d." The pattern continues with MAIN energy levels "4, 5, 6 and 7," but the higher sublevels of "5, 6 and 7" (those shown in parentheses above) do not appear in the standard electron configuration pattern, because there are only 117 known elements, so after 117, we don't have any more electrons to put into the higher orbitals. Each succeeding MAIN energy level has more orbital sublevels because as we move out from the nucleus of the atom, there is more room for more electrons which can have the same MAIN amount of energy but have different orientations in space and different angular momenta.
Now look at the small black raised numbers. The small raised numbers shown above in black are called "superscripts." Superscripts represent the maximum numbers of electrons each orbital sublevel can hold. An orbital sublevel may hold LESS electrons than its maximum, but it can never hold MORE.
http://education.jlab.org/qa/electron_config.html http://preparatorychemistry.com/Bishop_Chemistry_First.htm http://preparatorychemistry.com/Bishop_comp_electron_config_Flash1.htm http://electronconfiguration.info/
