| A | B |
|---|
| chemical symbol | A shorthand way to write the name of an element |
| protons | Atomic particle with a positive charge that is part of an atom's nucleus |
| neutrons | Atomic particle with no charge (neutral ) that is part of an atom's nucleus |
| electron cloud | region where electrons most probably are found surrpunding the nucleus of an atom |
| quarks | Very small particles of matter that make up protons and neutrons ; presently , six different types of querks are know |
| isotopes | Atoms of the same element that have different numbers of neutrons |
| average atomic mass | The averange mass of an element is the averange mass of the mixture of its isotopes |
| mass number | Sum of the number of protons and neutrons in an atom's nucleus |
