CHEMISTRY

3. An atom or molecule with a net electrical charge due to the loss or gain of one or more electrons.
6. The number of protons in the nucleus of an atom.
7. A substance that cannot be broken down into simpler substances by chemical means.
8. A mixture where one substance (the solute) is dissolved evenly throughout another substance (the solvent).
9. A chemical reaction where a substance combines rapidly with oxygen, releasing heat and light.

1. A chemical bond involving the sharing of electron pairs between atoms.
2. A substance that increases the rate of a chemical reaction without undergoing a permanent chemical change itself.
4. The region of space around the nucleus where electrons are most likely to be found.
5. The process by which a solid changes directly into a gas without first becoming a liquid (e.g., dry ice).
6. The basic unit of a chemical element.