Atomic Structure

3. The mass of a proton or a neutron
5. Horizontal rows on the periodic table that have outer electrons in the same shell
6. The smallest particle of an element
9. divider between metals and non-metals
12. A substance containing only one type of atom
13. Negatively charged particles that orbit the nucleus
15. The number of protons in an atom

1. The number of neutrons and protons added together
2. The amount of mass an electron has
4. Vertical columns on the periodic table that share properties and have the same number of valence electrons
7. Elements that are present as molecules in their pure form
8. When two or more atoms are bonded together
10. A substance containing more than one element in fixed ratios to each other
11. positive sub-atomic particle found in the nucleus
14. The charge on a Neutron