6? The nucleus of ? Li is a powerful absorber of neutrons. It exists in the naturally occurring metal to the extent of 7.5%. In the era of nuclear deterrence, large quantities of lithium were processed to remove ? Li for use in hydrogen bomb production. The lithium metal remaining after removal of ? Li was sold on the market, 6? 7? (a) What are the compositions of the nuclei of ? Li and ? Li? 6? 7? (b)The atomic masses of ? Li and ? Li are 6.015122 and 7.016004 amu, respectively. A sample of lithium depleted in the lighter isotope was found on analysis to contain 1.442% ? Li. What is the average atomic weight of this sample of the metal?
Solution : Step 1 : An atom consists of subatomic particles called electrons, protons and neutrons. Neutrons and protons make the nucleus. Electrons revolve around the nucleus. 6 7 (a) What are the compositions of the nuclei of Li and Li Li(Lithium) has an atomic number of 3. Atomic number gives number of protons and electrons, as in neutral state, atom consists of equal number of protons and neutrons. Mass number is the sum of number of protons and neutrons. In Li, 6 indicates th ass number. So, Number of p rotons = 3 Number of e lectrons = 3 Number of n eutrons = mass number - number of protons = 6 - 3 = 3. Step 2: In Li, 7 indicates the mass number. So, Number of p rotons = 3 Number of e lectrons = 3 Number of n eutrons = mass number - number of protons = 7 - 3 = 4.