2. 1. Proton 2. Neutron 3. Electron

3. 1. Protons 2. Neutrons 3. Electrons

4. 1. Protons 2. Neutrons 3. Electrons

5. 1. Protons 2. Neutrons 3. Electrons

6. 1. nuclide. 2. neutron. 3. electron. 4. isotope.

7. 1. nucleus. 2. empty space 3. electrons. 4. protons.

8. 1. principal chemical properties. 2. masses. 3. numbers of protons. 4. numbers of electrons.

9. 1. 6 2. 7 3. 8 4. 14 5. 20

10. 1. Carbon – 14 2. Nitrogen – 13 3. Nitrogen – 14 4. None of the above

11. 1. Proton 2. Neutron 3. Electron

12. 1. Proton 2. Neutron 3. Electron

13. 1. Proton 2. Neutron 3. Electron

14. 1. Proton 2. Neutron 3. Electron

15. 1. Mass number 21 2. Mass number 24 3. Mass number 25 4. All equal in abundance

16. 1. Mass number 7 2. Mass number 8 3. Mass number 9 4. All equal in abundance

17. 1. Atom 2. Element 3. Isotope 4. Ion

18. 1. Atom 2. Element 3. Isotope 4. Ion