| A | B |
|---|
| ionic bond | chemical bond formed by the attractive forces between two ions of opposite charge |
| compound | substance composed of atoms of two or more different elements that are chemically combined |
| nucleus | positively charged center of an atom |
| electron cloud | area around atom's nucleus that holds electrons |
| isotopes | atoms of the same element that have different numbers of neutrons in the nucleus |
| energy levels | specific regions around the nucleus where electrons exist |
| element | substance that cannot be broken down into simpler chemical substances |
| atom | smallest particle of an element that has the characteristics of that element |
| molecule | group of atoms held together by covalent bonds |
| protons | positively charged particles in atom nucleus |
| neutrons | particles in atom nucleus with no charge |
| covalent bond | force holding together two atoms sharing electrons |
| electrons | negatively charged particles in the space surrounding the nucleus |
| valence electrons | electrons in outermost energy level |
| atomic number | number of protons in an element |
