In relation to the atoms that form the matter, they are composed of a core, among which are positively charged protons and neutrons with a negative charge, on the other hand, around the core are the electrons that have negative charge. All elements have the same number of protons and electrons and that number is what determines the atomic number of an element. This means that it refers to the total number of protons in an atom. Consequently, it expresses the identity of an element.
Atomic number and mass number
To represent the atomic number, it is placed before the element. Thus, 5B indicates that the atomic number of boron is equal to 5, therefore, boron is an element with 5 electrons that circulate over the nucleus and another 5 protons inside the nucleus. On the other hand, boron has a series of neutrons, which are calculated by subtracting the mass number from the atomic number. So when boron has 11 neutrons and is subtracted by the corresponding atomic number, we get the mass number 6. In terms of indication, the mass number is placed on top of the atomic number of each element. With respect to terminology, the atomic number is symbolized by the letter Z and the mass number by the letter A.
If we take hydrogen as a reference, its atomic number is 1 and is represented as 1H, indicating that there is a proton in the nucleus of a hydrogen atom. In relation to the neutral atom , the number of protons is equal to the number of electrons, since in a neutral atom there is no total charge and the positive charges on the protons are balanced with the negative charges on the electrons.
The periodic table of elements and the atomic number
In the periodic table, the elements are grouped and organized according to their atomic number. The elements in this table can be divided into three groups : metals, non-metals and non-metals. Metals are great conductors of electricity and heat , while non-metals represent the opposite, while metalloids have intermediate characteristics between metals and non-metals.