Explain Atomic Weight of an element.

Atomic weight of an element is the relative weight of an element which is the number of times an atom of the element is heavier than `1/12` of an atom of C-12.

The unit of atomic weight is amu which is, 1 amu=`1/12*` weight of an atom of C-12.

The absolute weight of 1 amu is `1.66**10^-24 `kg.

Atomic weight can be determined by following three methods:

• Dulongs and Petits Method
• By the law of isomorphism

Dulongs and Petits Method:

Dulongs and Petits law states that the product of atomic weight and specific heat (cal/g) is approximately 6.4. i.e,

Atomic weight * specific heat = 6.4 (approx)

Thus, approximately atomic weight=6.4/ specific heat

Now the exact atomic weight can be determined if its equivalent atomic weight is known as,

Exact atomic weight=Valency * equivalent weight

By the law of isomorphism:

For element having two or more isotopes, atomic weight is the average weight of ....

Atomic weight of an element is the relative weight of an element which is the number of times an atom of the element is heavier than `1/12` of an atom of C-12.

The unit of atomic weight is amu which is, 1 amu=`1/12*` weight of an atom of C-12.

The absolute weight of 1 amu is `1.66**10^-24 `kg.

Atomic weight can be determined by following three methods:

• Dulongs and Petits Method
• By the law of isomorphism

Dulongs and Petits Method:

Dulongs and Petits law states that the product of atomic weight and specific heat (cal/g) is approximately 6.4. i.e,

Atomic weight * specific heat = 6.4 (approx)

Thus, approximately atomic weight=6.4/ specific heat

Now the exact atomic weight can be determined if its equivalent atomic weight is known as,

Exact atomic weight=Valency * equivalent weight

By the law of isomorphism:

For element having two or more isotopes, atomic weight is the average weight of all possible isotopes.

For example chlorine has two isotopes Cl-35 and Cl-37 with abundance 75% and 25% respectively. Now, the atomic weight of chlorine is:

`=(35**75+37**25)/100=35.5 a m u`