Multiple Choice
Which of the following represents the valence electron configuration for a neon (Ne) atom?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following represents the valence electron configuration for a beryllium (Be) atom?
A
2s^2
B
1s^2 2s^1
C
1s^2 2s^2 2p^2
D
2p^2
Verified step by step guidance1
Identify the atomic number of beryllium (Be), which tells you the total number of electrons in a neutral atom. Beryllium has an atomic number of 4, so it has 4 electrons.
Recall that electrons fill atomic orbitals in order of increasing energy, following the Aufbau principle. The order starts with 1s, then 2s, then 2p, and so on.
Write the full electron configuration for beryllium by placing 4 electrons in the lowest energy orbitals: 1s and 2s. This gives 1s^2 2s^2.
Determine the valence electrons by identifying electrons in the outermost shell (highest principal quantum number). For beryllium, the outermost shell is n=2, which includes 2s and 2p orbitals.
Extract the valence electron configuration from the full configuration by focusing on the electrons in the n=2 shell. Since beryllium has 2 electrons in the 2s orbital and none in 2p, the valence electron configuration is 2s^2.
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