Define isotope. Using 2 different elements, give examples of isotopes.Could you please give 2 examples(to help) using 2 different elements.

An isotope refers to atoms of an element which differ only
in the number of neutrons they have. An element is uniquely defined by the number of
protons it has. For example an atom with 6 protons in its nucleus is called a carbon
atom. The number of protons is called the atomic number and it is the same for all atoms
of a particular element.

In the case of isotopes of an
element the number of neutrons in the nucleus is different. For example, the atomic mass
of a normal carbon atom is 12 as it has 6 protons and 6 neutrons in its nucleus. The
isotope C-13 also has the same number of protons, i.e. 6, but the number of neutrons is
not 6 but 7. This makes the atomic mass 6+7 = 13.

As
another example of an isotope we could take tin. Tin has 50 protons and therefore an
atomic number of 50. But the number of neutrons in an atom of tin is 68 or 70 which
makes the atomic mass 118 or 120 resp.