1. A Review of General Chemistry

Look at the relative positions of each pair of atoms listed here in the periodic table. How many core electrons does each have? How many valence electrons does each have?

c. nitrogen and phosphorus

d. magnesium and calcium

How many valence electrons do chlorine, bromine, and iodine have?

Which is more stable, free hydrogen atoms or the diatomic H₂ molecule? Why do you know this to be true?