Resources | Subject Notes | Physics | Lesson Plan
The nucleus is the dense, central part of an atom. It contains protons and neutrons. The number of protons in the nucleus determines the element. A key concept is the relationship between the number of protons and the relative charge of the nucleus.
The proton number, often denoted by Z, is the number of protons in the nucleus of an atom. It is a unique characteristic of each element. For example, all atoms with 6 protons are carbon.
The relative charge of the nucleus is determined by the number of protons. Protons have a positive electrical charge. Therefore, the nucleus has a net positive charge equal to the number of protons.
The relative charge of the nucleus is directly proportional to the proton number. This means that the more protons in the nucleus, the greater the positive charge.
Property | Description |
---|---|
Proton Number (Z) | The number of protons in the nucleus of an atom. |
Relative Charge | The net electrical charge of the nucleus. Equal to the number of protons. |
Sign of Charge | Positive (+) |
Consider an atom of oxygen (O). Oxygen has an atomic number of 8, which means it has 8 protons. Therefore, the nucleus of an oxygen atom has a relative charge of +8.
The relative charge of the nucleus can be represented mathematically as:
$$ \text{Relative Charge} = \text{Number of Protons (Z)} \times \text{Elementary Charge} $$ $$ \text{Elementary Charge} = +1.6 \times 10^{-19} \text{ Coulombs} $$So, the relative charge of the nucleus is the number of protons multiplied by the elementary charge.
For example, an atom with 12 protons (Magnesium) would have a relative charge of: $$12 \times 1.6 \times 10^{-19} \text{ Coulombs} = 1.92 \times 10^{-18} \text{ Coulombs}$$
The positive charge on the nucleus is crucial for attracting and holding the negatively charged electrons in orbit around it, forming an atom.