Question
What is atomic number? How has this concept improved the definition of an element?
Solution
(i) Atomic number of an element is equal to the number of protons present in the nucleus of its atom.
∴
Atomic number = Number of unit positive charges on the nucleus.
Since the atom as a whole is electrically neutral, therefore, atomic number is the same as the number of electrons around the nucleus of an atom.
(ii) Atomic number gives the position of the element in the periodic table. In terms of atomic number an element can now be defined as a substance comprising of atoms all of which have the same atomic number.
