The atomic number of an element is directly related to the number of protons in the nucleus of an atom of that element. It represents a fundamental characteristic of each element and is denoted by the symbol Z.
In an electrically neutral atom, the number of protons is equal to the number of electrons. This balance of positive protons and negative electrons ensures that the overall charge of the atom is neutral.
For example, let's consider the element oxygen (O) with atomic number 8. This means that an oxygen atom contains 8 protons in its nucleus. Since it is neutral, it also has 8 electrons surrounding the nucleus.
The atomic number determines the identity of an element because it is unique to each element. Elements with different atomic numbers have different numbers of protons, which is what defines their chemical properties and place in the periodic table.
In summary, the atomic number of an element corresponds to the number of protons in the nucleus and is equal to the number of electrons in a neutral atom of that element.