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Unformatted text preview: as only two
s electrons in its valence shell, and no d electrons anywhere in its
configuration. The other element has d electrons in its configuration.
The elements are:
neither of these contain dae-Mg and Ca
K has 1 electron in valence shell
b. K and Rb
2 valence in Ca
c. Ca and Sr
d. Al and Ga 13 05-Sep-13 Orbital energy in polyelectronic atoms
Let’s look at the orbital energy diagrams for a many-electron atom.
What do you notice??
3d has a higher energy
energy level then 4s.
4p is more energetic then
3p.4s is closer to the
nucleus. more stable.
Na- 2 eNeon- 10 e-,10 p+
all these electrons are
feeling the pull of
protons. increase no. of
protons- more attraction for
4s e- will feel the pull
of nucleus then more then
3d.as it is closer.
this logic also applies
to 5s and 4d, 5p and 4d, 5e and 4f. So what’s going on???
Answer: A 4s orbital shape penetrates
closer to the nucleus than does a 3d
shape, so it is screened less from the
nuclear charge and therefore gains
extra stability relative to the 3d orbital. Effective nuclear charge, shielding,...
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