Atoms and Molecules

3. When two or more compounds combine without participating in a chemical change.
5. A neutral group of two or more atoms held together by chemical bonds.
6. Arrangement of elements on a table based on their atomic number
8. Point at which a liquid is turned into a gas.
10. Region inside the atom where electrons are likely to be found.
11. Particle in the nucleus with no charge.
12. The lightest element known.
13. Any one of several types of very small particles that make up matter.
14. The point at which a solid turns to a liquid.
16. The basic unit of matter.
18. A pure substance containing just one type of atom.
19. A type of chemistry that studies carbon-based life forms.
21. The number of protons in the nucleus of an element.

1. Particles like protons, neutrons, and electrons that are smaller than atoms.
2. Molecules made up of two or more different elements.
4. Particle in the nucleus that is positively charged.
7. Creator of the Periodic Table
9. The tiny, dense positively charged region in the center of an atom where protons and neutrons are housed.
10. Negatively charged particle that travels around the nucleus of an atom.
15. Anything that occupies space and has mass.
17. Greek scientist and philosopher who developed the theory of the atom.
20. The three common states of matter are solid, liquid, and __________.