p. 77

6.Mg-24: 12 Protons,12 Neutrons. Mg-25: 12 Protons, 13 Neutrons. Mg-26: 12 Protons, 13 Neutrons.

7. The mass of the electron is much less than the mass of the proton or neutron, as the electron is very tiny so it weighs less.

8. This information is not sufficient because it is important to know some deep characteristics of the element in order to have a strong prediction. But, all he has is the element's mass which is not enough information.

9. a. Period b. Group or family

10. Beryllium (Be) and Sodium (Na).

p. 57

2. A. No, 1-
    B. No, 3+
    C. No, 3+
    D. No, 2+
    E. Yes!

Thanks so much!
Forever and Always,
Abi