# Design And Composition Of Pennies

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Pennies have undergone design and composition changes over the years. Just like pennies have several versions, atoms of elements also have different versions of each other called isotopes. In this lesson, we will learn how to find the average atomic mass of the elements from its isotopes.

!!!Average Atomic Mass

Have you ever gone through a whole bag of multi-colored M&M’s? If you look inside the bag of M&M’s, the shape and size of each M&M is relatively the same. However, there are different colors. If we count how many M&M’s there are for each color, sometimes we find that the most popular color in one bag is brown, and the other times, it is green or yellow.

Colorful M&M’s

Have you ever wondered how pennies have changed over the years? The penny has undergone several design changes, and composition changes – some pennies are made purely of copper, some have nickel, tin and zinc. If we …show more content…

__Isotopes__ are different versions atoms of the same element with a different number of neutrons and different atomic masses.

The whole numbers on the isotopes (superscript on the upper left side of the elements) are rounded to the nearest whole number of the mass that is indicated beside the element in the tables. When we see the atomic masses of elements in the periodic table, these are actually the averages of the atomic masses of their different isotopes. Isotopes of an element have different natural abundances, as shown in the tables below. The __natural abundance__ indicates the percentage of the isotope that is naturally found on the planet.

The __average atomic mass__ of an element refers to the atomic masses of the isotopes of the element, taking into account the different abundances of the element’s isotopes. The average atomic mass can be calculated using the following