Isotopes are the substances having same atomic number but different

Isotopes- Definition with Example
Isotopes are the different forms of same element having same number of protons but different number of neutrons. Suppose, we talk of isotopes of carbon. You might have heard about Isotopes of carbon. These are C-12, C-13 and C-14. Here, mass number of C-12 isotope is 12 and that of C-13 isotope is 13. Theoretically, Mass number is equal to the sum of number of protons and number of neutrons in an atom of a particular element.

Atomic number of all the isotopes of carbon whether it is C-12, C-13 or C-14 is 6. But

Number of neutrons in C-12 = 6
Number of neutrons in C-12 = 7
Number of neutrons in C-12 = 8

Elements and Compounds
Elements are the substances that have one kind of atoms.For example, hydrogen is an element. It contains only H atoms. But if we talk of compounds, they contain more than one kind of atoms such as HCl. Hydrogen Chloride contains atoms of Hydrogen and Chlorine. So, it is a compound.