Across
- 2. The tiny, very dense, positively charged region in the center of an atom that is made up of protons and neutrons
- 4. The smallest particle of an element; made of electrons, protons, and neutrons
- 5. A pure substance composed of the same type of atom throughout
- 6. The rows in a periodic table that classify the elements by the number of electron shells
- 7. Elements that have properties of both metals and nonmetals
Down
- 1. A conceptual model of the atom in which a small, positively charged nucleus is surrounded by planetary electrons
- 2. Nonreactive nonmetals in Group 18 of the periodic table
- 3. The columns on a periodic table that arrange the elements by the number of electrons that are in the outermost shell