Chemistry terms

2. the unit of arrangement in a periodic table in which all elements have the same number of electrons in the outer shell
6. - elements in the group 7.
7. - the most abundant gas in the air.
9. formed when 2 or more chemical elements combine in fixed proportions.
11. a subatomic particle with a positive charge found in nucleus
13. the solution which contains as much dissolved solid as possible at the particular temperature
16. the atoms of the same elements that have different number of neutrons.
17. a subatomic particle with a negative charge found in the atom shells.
18. an atom that has lost or gained electrons

1. consists of two or more atoms chemically bonded by covalent bonds.
3. the spreading out of particles in a gas or a liquid
4. the process of transition of matter from solid to liquid state
5. a subatomic particle with no charge found in nucleus
8. - the second most abundant gas in the air.
10. can be used to separate the components of a solution.
12. the atoms of this element have 16 protons in their nuclei.
14. the unit of the amount of substance
15. the horizontal row in the periodic table in which all elements have the same number of shells.