1.
A negatively charged particle found outside the nucleus.
2.
A vertical column on the periodic table; main-group elements in the same group have similar valence-electron patterns.
3.
The smallest unit of an element that still has the properties of that element.
4.
A positively charged ion formed when an atom loses electrons.
5.
An element that generally tends to gain or share electrons and may form negative ions.
6.
A particle with no charge found in the nucleus of an atom.
7.
An electron in the outermost energy level of an atom.
8.
A pure substance made of only one type of atom.
9.
A negatively charged ion formed when an atom gains electrons.
10.
A horizontal row on the periodic table; the period generally indicates the highest occupied main energy level of an atom.
11.
The small, dense center of an atom that contains protons and neutrons.
12.
An element that generally tends to lose electrons and form positive ions.
13.
A positively charged particle found in the nucleus of an atom.
14.
An atom or group of atoms that has gained or lost electrons and therefore has a charge.
15.
Atoms of the same element that have different numbers of neutrons.
