Chemistry: Atomic Structure & Periodicity Flashcards
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Photoelectron spectroscopy (PES) of an element shows peaks at binding energies corresponding to 1s, 2s, and 2p with relative heights 2:2:4. The element is:
Answer: Oxygen
Heights 2:2:4 give 8 electrons total, matching oxygen (1s^2 2s^2 2p^4).
In a PES spectrum, the peak at the highest binding energy corresponds to electrons that are:
Answer: Closest to the nucleus
Core electrons closest to the nucleus are held most tightly and have the highest binding energy.
The peak height in a PES spectrum is proportional to:
Answer: The number of electrons in that subshell
PES peak intensity reflects how many electrons occupy that subshell.
Coulomb's law predicts that the binding energy of an electron increases when:
Answer: Nuclear charge increases
Greater nuclear charge increases the attractive force, raising binding energy.
Compared to sodium, the 1s electrons of magnesium have a higher binding energy because magnesium has:
Answer: A greater nuclear charge
Magnesium's extra proton pulls the 1s electrons more strongly than sodium's nucleus does.
A PES spectrum with peaks at 1s, 2s, 2p, and 3s, where the 3s peak is half the height of the 2s peak, indicates the element:
Answer: Sodium
A 3s peak half the 2s height means 1 electron in 3s, giving sodium (1s^2 2s^2 2p^6 3s^1).
Why do 2s electrons have a higher binding energy than 2p electrons in the same atom?
Answer: 2s electrons penetrate closer to the nucleus
The 2s orbital penetrates nearer the nucleus, experiencing less shielding and stronger attraction.