Question

17. Find the average atomic mass unit of silicon given the following isotopes and

abundances: Silicon-28, Silicon-29, Silicon-30 with masses of 27.977, 28.976,
29.974, respectively. The percent abundance of the silicon isotopes is 92.2%, 4.7%
and 3.1%, respectively. Periodic table and it’s trends

Answer 1

The average atomic mass unit of Silicon : 28.0774

Further explanation

Given

Isotopes of Si(Silicon-28, Silicon-29, Silicon-30)

Required

The average atomic mass

Solution

Isotopes are elements that have the same Atomic Number (Proton)

Atomic mass is the average atomic mass of all its isotopes

Avg. atomic mass = %mass.isotopes 1 + %mass.isotopes 2...etc

Input the values :

Avg atomic mass = (0.922 x 27.977) + (0.047 x 28.976) + (0.031 x 29.974)

Avg atomic mass = 28.0774