chemistry vocabulary

4. the number of positive charges of protons in the nucleus of an atom of a given element
5. any of two or more forms of a chemical element
7. any element in group 2 of the periodic table
8. an ionic bond is a chemical link between two atoms caused by an electrostatic force
10. samples of a pure compound always contain the same elements
14. any of the set of metallic elements in groups 4-12 of the periodic table
17. molecules composed only of two metals
20. any element in group 17 of the periodic table
21. a positively charged elementary that is a fundamental constituent of all atomic nuclei

1. an element whose properties are intermediate between metals and solid non metals
2. an ionic species having a negative charge
3. a representation of a substance using symbols for its constituent elements
6. theory that matter consists of of invisible particles called atoms
9. a table of chemical elements arranged in order of atomic number
11. any of the elements in group ia 1 of the periodic table
12. an atom or molecule with a net electric charge due to the loss or gain of one or more electrons
13. a positively charged ion
15. any of the gases in group O (18) of the periodic table
16. a fundamental group of atoms in a molecule serving as a base
18. the integer number nearest in value to the atomic weight of an atom and equal to the number of nucleons
19. an elementary particle that is a fundamental constituent of matter