My Teacher didn't teach us this please help

What is the percent by mass of oxygen in fe2o3

The point along a planet's orbit where it is closest to the sun is called the

Acertain atom has 22 protons and 19 electrons. this atom loses an electron. the net charge on the atom is now 4+1+01-4-. if this same atom with 22 protons and 19 electrons were to gain 3 electrons, the net charge on the atom would be 3+2+02-3-.