2. Determining the NUMBER of Protons Electrons and Neutrons in Atoms, Ions, and Isotopes

4. NUMBER of PROTONS For any given element, the number of protons equal the atomic number 12 Mg 24.30 ATOMIC NUMBER

5. Examples 6 6 26 28 53 56

6. NUMBER of ELECTRONS For any given element, the number of electrons equal the protons. 12 Mg 24.30 Number of protons or Atomic Number

7. Examples 6 6 26 28 53 56 6 26 28 53 56

8. NUMBER of NEUTRONS For any given element, the number of neutrons plus protons equal the mass number. 12 Mg 24.30 ATOMIC MASS

10. Ions Substances that have a positive or negative charge. Created by the change in ELECTRONS. Protons and Neutrons are determined in the same way as atoms.

11. Number of Electrons in Ions The number of electrons may be calculated as: S 2- 16 - (-2) = 18 Charge of the ion

12. Examples 11 35 10 36 13 10 8

14. Isotopes Substances that have the same atomic number but different mass numbers Created by the change in NEUTRONS. Protons and Electrons are determined in the same way as atoms.

15. Number of Neutrons in Isotopes The number of neutrons may be calculated as: H-1 H-2 H-3 Mass Number

16. Examples 12 14 6 8 238146 235143