The atomic number of an atom is the number of protons in the nucleus of the atom, while the mass number is the total number of protons and neutrons in the nucleus. The atomic number is unique to each element and determines the identity of the element, while the mass number is a measure of the mass of the atom and can vary within an element.
Atoms are electrically neutral when the number of protons in the nucleus is equal to the number of electrons orbiting the nucleus. This means that the positive charge of the protons is balanced by the negative charge of the electrons, resulting in an overall neutral charge for the atom.
The atomic number of each atom represents the number of protons in the nucleus of the atom. This number is unique to each element and determines the identity of the element. For example, the atomic number of hydrogen is 1, which means that it has one proton in its nucleus and is therefore a unique element. The atomic number is used to arrange the elements in the periodic table and is an important property of atoms.