Atoomnummer en massagetal

The atomic number, denoted as Z, is the total number of protons in the nucleus of an atom.

On the periodic table, each square represents an element having a unique atomic number. These elements are arranged in order of increasing atomic number.

An atom with one proton is hydrogen, an atom with two protons is helium, and so on.

The mass number of an atom is the sum of the protons and neutrons in the atomic nucleus,  represented by the letter A.

So, a hydrogen atom with one proton and no neutrons has a mass number of one, while a helium atom with two protons and two neutrons has a mass number of four.

Elements can have multiple isotopes with the same number of protons but different numbers of neutrons.

For example, carbon atoms exist as carbon-12 with six protons and six neutrons, carbon-13 with six protons and seven neutrons, or carbon-14 with six protons and eight neutrons.