How does a chlorine atom become a negatively charged ion?

• A. By gaining one electron
• B. By losing one electron
• C. By losing one neutron
• D. By gaining one proton

Answer: (A)

Verified step by step guidance

1. Understand that an atom becomes an ion by gaining or losing electrons, which changes its net electric charge.
2. Recall that chlorine (Cl) is a halogen with 7 valence electrons and tends to achieve a full octet by gaining electrons.
3. Recognize that gaining one electron will give chlorine a total of 8 valence electrons, making it more stable and negatively charged.
4. Note that losing electrons would make the atom positively charged, which is not typical for chlorine in forming ions.
5. Conclude that a chlorine atom becomes a negatively charged ion (Cl⁻) by gaining one electron.