Answer: A sodium atom has one electron in its outer shell. The atom is more stable if it has a full outer shell. A sodium atom can lose its outer electron. It will still have 11 positive protons but only 10 negative electrons.
Valence electrons the outermost electrons, and are the ones involved in bonding. Sodium has 11 electrons: its atomic number is 11, so it has 11 protons; atoms are neutral, so this means sodium also has 11 electrons.
