Multiple Choice
Which classification of atoms typically form anions?
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2. Atoms & Elements
Ions
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How many electrons does a chlorine atom gain to achieve a stable electron configuration?
A
8
B
7
C
1
D
2
Verified step by step guidance1
Identify the atomic number of chlorine, which is 17. This means a neutral chlorine atom has 17 protons and 17 electrons.
Determine the electron configuration of chlorine. The electrons fill orbitals in the order: 1s, 2s, 2p, 3s, and 3p. For chlorine, the configuration is $1s^2 2s^2 2p^6 3s^2 3p^5$.
Recognize that a stable electron configuration often corresponds to a full outer shell, typically resembling the nearest noble gas configuration. For chlorine, the nearest noble gas is argon, which has a full outer shell with 8 electrons in the third shell.
Count how many electrons chlorine needs to gain to fill its outermost shell. Since chlorine has 7 electrons in its outer shell (3s and 3p orbitals combined), it needs to gain 1 electron to reach 8 electrons and achieve stability.
Conclude that chlorine gains 1 electron to achieve a stable electron configuration, forming a chloride ion (Cl⁻) with a full octet.
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