Question

which is the atomic number of an atom with six valence electrons?
a 6
b 8
c 12
d 10

Explanation:

Step1: Recall valence electron rules

Valence electrons depend on electron configuration. For main - group elements, valence electrons are related to the group number. The electron configuration of an atom with atomic number \(Z\) follows the Aufbau principle.

Step2: Analyze each option

• Option A (atomic number 6, carbon): Electron configuration is \(1s^{2}2s^{2}2p^{2}\), valence electrons = 4.
• Option B (atomic number 8, oxygen): Electron configuration is \(1s^{2}2s^{2}2p^{4}\), valence electrons = 6 (since the outermost shell has \(2s^{2}2p^{4}\), total of \(2 + 4=6\) valence electrons).
• Option C (atomic number 12, magnesium): Electron configuration is \([Ne]3s^{2}\), valence electrons = 2.
• Option D (atomic number 10, neon): Electron configuration is \([He]2s^{2}2p^{6}\), valence electrons = 8 (noble gas, full outer shell).

Answer:

B. 8