The two most abundant isotopes of carbon are carbon-12 (mass = 12.00 amu) and carbon-13 (mass = 13.00 amu). their relative abundances are 98.9% and 1.10%, respectively. calculate the average atomic mass of carbon.

The answer to your question is: Average atomic mass = 12.011 amu

Explanation:

Data

Carbon -12   mass 12 amu   abundance = 98.9%

Carbon -13   mass 13 amu   abundance = 1.10%

Average atomic mass = ?

Process

Average atomic mass = (Isotope1 x abundance) + (Isotope2 x abundance)

Average atomic mass = (12 x 0.989) + (13 x 0.011)

Average atomic mass = 11.868 + 0.143

Average atomic mass = 12.011

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.