Vocabulary

4. The electrons in the outermost shell of an atom; they determine how an atom bonds.
10. The number of protons in an atom; identifies the element.
12. A substance made of two or more elements that are chemically combined.
13. Table A chart that organizes all known elements by their properties and atomic number.
14. A horizontal row on the periodic table; elements in the same period have the same number of energy levels.
15. The total number of protons and neutrons in the nucleus.

1. A pure substance made of only one kind of atom.
2. Two or more atoms bonded together.
3. The smallest particle of an element that still has the properties of that element.
5. The force that holds atoms together in a molecule or compound.
6. A negatively charged particle that orbits the nucleus of an atom.
7. A positively charged particle in the nucleus of an atom.
8. A neutral particle in the nucleus of an atom.
9. A vertical column on the periodic table; elements in the same group share similar properties.
11. The dense center of the atom that contains protons and neutrons.