What is Atomic Mass?

Atomic mass is a measure of the amount of matter contained in an atom, or in other words, it is a measure of the heaviness of the atom. The atomic mass is measured in atomic mass units (amu) and is represented by the symbol u. An atomic mass unit is defined as 1/12th of the mass of a single atom of carbon-12.

Atomic Mass vs Atomic Weight

Atomic mass and atomic weight are commonly used interchangeably, but they are actually two separate measurements. The atomic mass or relative atomic mass is the measurement of the average masses of all the isotopes of an element, compared to the relative mass of a single atom of carbon-12. On the other hand, the atomic weight (or average atomic mass) is the measurement of the average mass of a single atom of an element, based on the weighted average mass of its naturally occurring isotopes.

Factors that Influence the Atomic Mass

Atomic mass is affected by several different factors, such as the number of protons and neutrons contained in the nucleus, the number of electrons surrounding the nucleus, and the chemical environment.

The number of protons and neutrons contained in the nucleus affects the mass because each of these particles has a different mass. For example, a proton has a mass of 1.67262 x 10-27 kg, and a neutron has a mass of 1.67493 x 10-27 kg. The number of electrons surrounding the nucleus also affects the mass because electrons have a relatively small mass compared to protons and neutrons.

Finally, the chemical environment also affects the mass because different elements can form bonds with other elements, thus increasing their mass. For example, one atom of oxygen can form bonds with two atoms of hydrogen to form the molecule water (H2O). In this case, the atomic weight of water would be greater than the sum of the atomic masses of the individual atoms of oxygen and hydrogen.

Conclusion

The atomic mass is a measure of the amount of matter contained in an atom, represented by the symbol u. Atomic mass and atomic weight are not the same measurement, as atomic mass is a measure of the average mass of all the isotopes of an element, while atomic weight is a measure of the average mass of a single atom of an element. Atomic mass is affected by different factors, such as the number of protons and neutrons contained in the nucleus, the number of electrons surrounding the nucleus, and the chemical environment.