Answer:
The top left number of the symbol of an atom is the sum of the protons and neutrons in the atom known as atomic mass number, while the bottom left number of the symbol of an atom is the number of protons in the atom known as atomic number.
Explanation:
An atom of an element is composed of other subatomic particles; the electron, proton and neutron. The number of protons present in an atom of an element is equal to the number of electrons present in the atom of that element and is known as the atomic number of the element. The number of neutrons present in the atom summed together with the proton number gives the atomic mass number of an atom of the element.
Elements are represented with symbols. In writing the symbols of elements, the atomic number and the atomic mass of an atom of the element is usually written along with the symbol. The top left number of the symbol of an atom is the sum of the protons and neutrons in the atom, while the bottom left number of the symbol of an atom is the number of protons in the atom.
For example, the element sodium has an atomic number of 11 and a mass number of 23. In symbols, it is written as follows: ²³₁₁Na
