Atoms

4. The dense, central core of an atom, containing the protons and neutrons.
5. A chart organizing all known elements based on their atomic number and properties.
10. A vertical column in the periodic table containing elements with similar chemical properties.
11. A process that results in the formation of new substances with different properties.
14. A negatively charged particle that orbits the nucleus of an atom in layers or shells.

1. A neutral particle with no electric charge, also located in the atom's nucleus.
2. A change in the form or appearance of a substance without making a new substance.
3. The starting substance(s) in a chemical reaction that are used up or transformed.
5. The new substance(s) formed as a result of a chemical reaction.
6. A substance formed when two or more different elements are chemically bonded together.
7. A pure substance that cannot be broken down into simpler substances by chemical means.
8. A horizontal row in the periodic table; properties change gradually across a period.
9. A group of two or more atoms held together by strong chemical bonds.
12. The smallest unit of an element that still has the properties of that element.
13. A positively charged particle found in the nucleus, or center, of an atom.