Atoms and the Periodic Table

3. A negatively charged subatomic particle that moves in the space outside the nucleus.
7. Elements that are poor conductors, often exist as gases, and are brittle in solid form.
9. The tiny, dense, positively charged region at the center of an atom.
10. NUMBER The unique number of protons in an atom that identifies each element.
11. NUMBER The sum of the protons and neutrons in the nucleus of an atom.
12. A positively charged subatomic particle located inside the nucleus.
14. ELECTRON An electron in the highest occupied energy level of an atom, key to chemical reactivity.
16. LEVELS Areas located at fixed distances from the nucleus where electrons can be found.
18. Atoms of the same element that have different numbers of neutrons.
19. A horizontal row in the periodic table.

1. Highly reactive nonmetals in Group 7A (or 17).
2. A charged particle formed when an atom gains or loses one or more electrons.
4. A vertical column in the periodic table containing elements with similar properties.
5. METALS Extremely reactive metals in Group 1A with only one valence electron.
6. Elements that are generally good conductors of heat and electricity and are mostly solids at room temperature.
8. CLOUD A visual model used to describe the most likely locations of electrons in an atom.
11. Elements located along a zigzag line that have properties between metals and nonmetals.
13. GASES Colorless, odorless, and extremely unreactive gases found in Group 8A.
15. A neutral subatomic particle found in the nucleus with a mass almost equal to a proton.
17. The fundamental building blocks of all matter.