Chapter 1

6. An average value that takes account of the abundance of the isotopes of the element.
8. The collection of metallic elements in the middle of the periodic table.
11. The elements in Group 7 of the periodic table.
12. This atomic model stated that the mass was concentrated at the centre of the atom and that the nucleus was charged.
13. Atomic model devised after the discovery of the electron. The model suggests the atom is a ball of positive charge with negative electrons scattered through it.
15. Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table.
16. gases The elements in Group 0 of the periodic table.

1. Elements that react to form negative ions. Found towards the right and top of the periodic table.
2. Table of elements arranged in order of atomic number and such that elements with similar properties are in the same column (group).
3. Positively charged subatomic particle present in the nucleus of the atom. Relative mass of 1.
4. A mixture consists of two or more elements or compounds not chemically combined together.
5. Atoms of the same element with the same number of protons but a different number of neutrons.
7. The total number of protons and neutrons in the nucleus.
9. Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1.
10. An atom or molecule with an electric charge due to the loss or gain of electrons.
14. A procedure by which two liquids with different boiling points can be separated.