Multiple Choice
Which of the following represents the complete ground state electron configuration for a manganese (Mn) atom?
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10. Periodic Properties of the Elements
The Electron Configuration
Multiple Choice
How many unpaired electrons are present in a neutral beryllium (Be) atom?
A
0
B
2
C
4
D
1
Verified step by step guidance1
Identify the atomic number of beryllium (Be), which tells you the number of electrons in a neutral atom. Beryllium has an atomic number of 4, so it has 4 electrons.
Write the electron configuration for beryllium by filling the orbitals in order of increasing energy. The order starts with 1s, then 2s, then 2p, etc. For Be, the configuration is \(1\mathrm{s}^2 2\mathrm{s}^2\).
Recall that each orbital can hold a maximum of 2 electrons with opposite spins, so the 1s orbital is fully filled with 2 electrons, and the 2s orbital is also fully filled with 2 electrons.
Determine the number of unpaired electrons by checking if any electrons occupy orbitals singly. Since both 1s and 2s orbitals are fully paired, there are no unpaired electrons in a neutral Be atom.
Conclude that the number of unpaired electrons in a neutral beryllium atom is 0.
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