Electron Chemistry Example 2

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Example 2

medium
A chlorine atom (Z=17Z = 17) gains one electron. Write the electron configuration of the resulting Cl−\text{Cl}^- ion and explain why chlorine tends to gain an electron.

Solution

  1. 1
    Neutral Cl: 1s2 2s2 2p6 3s2 3p51s^2\,2s^2\,2p^6\,3s^2\,3p^5 (17 electrons).
  2. 2
    Cl−\text{Cl}^- gains one electron: 1s2 2s2 2p6 3s2 3p61s^2\,2s^2\,2p^6\,3s^2\,3p^6 (18 electrons).
  3. 3
    This gives Cl−^- a complete octet in its outer shell (3s2 3p63s^2\,3p^6), matching the noble gas argon configuration.

Answer

Cl−:1s2 2s2 2p6 3s2 3p6\text{Cl}^-: 1s^2\,2s^2\,2p^6\,3s^2\,3p^6
Atoms tend to gain or lose electrons to achieve a stable noble gas electron configuration. Chlorine needs only one more electron to fill its 3p3p subshell, which is why it readily forms Cl−\text{Cl}^-.

About Electron

A negatively charged subatomic particle with negligible mass that occupies energy levels (shells) outside the nucleus.

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Example 4 medium

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