Multiple Choice
How many valence electrons does an oxygen (O) atom have?
3
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many electrons are present in the third shell (n = 3) of a sodium (Na) atom in its ground state?
A
8
B
2
C
11
D
1
Verified step by step guidance1
Identify the electron configuration of a sodium (Na) atom in its ground state. Sodium has an atomic number of 11, meaning it has 11 electrons.
Write the electron configuration using the Aufbau principle: fill orbitals in order of increasing energy levels. For sodium, the configuration is 1s\^2 2s\^2 2p\^6 3s\^1.
Recognize that the principal quantum number n = 3 corresponds to the third shell, which includes the 3s, 3p, and 3d subshells.
Count the electrons in the third shell based on the electron configuration. In sodium's ground state, only the 3s subshell has electrons, specifically 1 electron.
Conclude that the number of electrons in the third shell (n = 3) of sodium in its ground state is 1.
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