Nuclear Notation
- All matter is made from atoms
- Atoms are made up of three subatomic particles:
- Protons
- Neutrons
- Electrons
Structure of the Atom
Protons and neutrons are found in the nucleus of an atom while electrons orbit the nucleus
- Each of these subatomic particles has a mass and a charge
- Charge can be expressed in coulombs (C), or units of elementary charge e
- Mass can be expressed in kilograms (kg), or in atomic mass units u
Table of properties of subatomic particles
| particle | charge / C | charge / e | mass / kg | mass / u |
| proton | +1.60 × 10−19 | +1 | 1.673 × 10−27 | 1.007276 |
| neutron | 0 | 0 | 1.675 × 10−27 | 1.008665 |
| electron | −1.60 × 10−19 | −1 | 9.109 × 10−31 | 0.000549 |
- A nucleus can be described using
notation
notation is used to describe the constituents of a nucleus
- The top number A represents the nucleon number or the mass number
- Nucleon number (A) = total number of protons and neutrons in the nucleus
- The lower number Z represents the proton or atomic number
- Proton number (Z) = total number of protons in the nucleus
Exam Tip
In Chemistry, you may see nucleon number referred to as mass number and proton number as atomic number. Both of these are valid, just make sure you don't mistake mass number for atomic number, or vice versa.
Make sure you know that the periodic table is ordered by atomic number