Nitrogen has two isotopes. One has an atomic mass of 14.003 amu and a relative abundance of 99.63% while the other isotope has an atomic mass of 15.000 amu and a relative abundance of 0.37%. What is the average atomic mass for nitrogen?

Average atomic mass = 14.0067  amu.

Explanation:

Given data:

Abundance of 1st isotope  = 99.63%

Atomic mass of 1st isotope = 14.003 amu

Abundance of 2nd isotope  = 0.37%

Atomic mass of 2nd isotope = 15.000 amu

Solution:  

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass = (99.63×14.003)+(0.37×15.000) /100

Average atomic mass =  1395.119 + 5.55 / 100

Average atomic mass  = 1400.67 / 100

Average atomic mass = 14.0067  amu.

they are made of gases.

they have a spherical shape.

they make energy through fusion.