Q36P - Chemistry: Molecular Nature Of Matter And Change

Question

Define atomic number and mass number which can vary without changing the identity of the element?

Step-by-Step Solution

Answer

The atomic number of an element is the number of protons in the nucleus of an atom. The mass number of an element is the sum of several protons and neutrons present in the nucleus of an atom. The mass number can vary without changing the identity of an element.

Step 1: Atomic number of an atom.

The atomic number of an element is the number of protons in the nucleus of an atom. Each atom of a particular element has the same atomic number and different elements have different atomic numbers. The atomic number is represented by Z.

For example; The number of protons in the nucleus of Sodium is 11. Hence an atomic number of Sodium is 11.

Step 2:Mass the number of an atom.

The mass number of an element is the sum of several protons and neutrons present in the nucleus of an atom. Each proton and neutrons contribute one unit to the mass number.

For example; The sodium atom has protons 11 and neutrons 12 in its nucleus and has a mass number 12 of u.

Step 3:Variation without changing identity:

The mass number of an element can vary without changing the identity of an element as the atoms of the same element can have different mass numbers due to the different number of neutrons present in the nucleus, they are called isotopes.