Answers are:
1) Each sodium atom loses one electron.
2) The charge of the chloride ion in NaCl is -1.
Oxidation reaction: Na⁰ → Na⁺¹ + e⁻ /×2; 2Na⁰ → 2Na⁺¹ + 2e⁻.
Reduction reaction: Cl₂⁰ + 2e⁻ → 2Cl⁻.
Sodium change lose electrons and change oxidation number from 0 to +1 (oxidation). Chlorine change oxidation number from 0 to -1 (reduction reaction).