The atomic number is represented by the letterZ. It is the number of protons in the nucleus of an atom. The atomic number is a unique identifier for each element, and it determines the chemical properties of the element.

• For example, all hydrogen atoms have an atomic number of 1, which means that they all have one proton in their nucleus. All carbon atoms have an atomic number of 6, which means that they all have six protons in their nucleus.
• The atomic number is also used to organize the elements in the periodic table. The elements are arranged in order of increasing atomic number, from left to right. This means that all of the elements in a row have the same number of shells around their nucleus.
• The atomic number is a very important concept in chemistry, and it is used to explain a wide range of phenomena, from the chemical bonding of atoms to the properties of materials.