The element nitrogen has an atomic weight of 14.0 and consists of two stable isotopes nitrogen-14 and nitrogen-15. The isotope nitrogen-14 has a mass of 14.0 amu and a percent natural abundance of 99.6 %. The isotope nitrogen-15 has a percent natural abundance of 0.370 %. What is the mass of nitrogen-15? amu

Answer :  The mass of nitrogen-15 is, 15.1 amu

Explanation :

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

  .....(1)

For isotope:

Mass of isotope = 14.0 amu

Fractional abundance of isotope = 99.6 % = 0.996

For isotope:

Mass of isotope = ?

Fractional abundance of isotope = 0.370 % = 0.00370

Average atomic mass of nitrogen = 14.0 amu

Now put all the given values in equation 1, we get:

Therefore, the mass of nitrogen-15 is, 15.1 amu

pure substance: iron,copper

impure substance: water,charcoal

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.