Electron Shells in Atoms

# Electron Shells in Atoms - s and 2 p electrons combine to...

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Electron Shells in Atoms When we move down the column of the periodic table, we change the principle quantum number 'n' of the valence electrons of the atom We have referred to all orbitals with the same principle quantum number 'n' as a shell What does the quantum mechanical description of probability distributions for all electrons in an atom look like? He 1s 2 Ne 1s 2 2s 2 2p 6 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 The overall electron distribution can be calculated using supercomputers and the result is a spherically symmetrical distribution termed radial electron density Helium shows a single "shell" Neon shows two "shells" Argon shows three "shells" Each of these maxima corresponds to electrons that have the same principle quantum number 'n'

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In He the 1 s electrons have a maximum probability distribution at around 0.3 Å from the nucleus In Ne the 1 s electrons have a maximum at around 0.08 Å, and the 2 s and 2 p electrons combine to form another maximum at around 0.35 Å (the n =2 "shell") In Ar the 1 s electrons have a maximum at around 0.02 Å, the 2
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Unformatted text preview: s and 2 p electrons combine to form a maximum at around 0.18 Å and the 3 s and 3 p electrons combine to form a maximum at around 0.7 Å Why is the 1s shell in Argon so much closer to the nucleus than the 1s shell in Neon, and why is that closer than the 1s shell in helium? • The nuclear charge (Z) of He = 2+, Ne = 10+, Ar = 18+ • The inner most electrons (1s shell) are not shielded by other electrons, therefore the attraction to the nucleus is greater with higher number of protons • Likewise, the n=2 shell of Ar is closer to the nucleus than the n=2 shell of Ne. The Z eff for the 2s subshell of Ne would be (10-2) = 8+, and for Ar would be (18-2) = 16+. Thus, the 2s subshell electrons in Ar would be closer to the nucleus due to the greater effective nuclear charge . Three properties that provide important insights into chemical behavior include: 1. atomic size 2. ionization energy 3. electron affinity...
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Electron Shells in Atoms - s and 2 p electrons combine to...

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