How to Find Atomic Mass Using the Periodic Table

Finding the atomic mass of an element is easy if you follow these steps. The atomic mass is the average weight of all the natural forms, called isotopes, of that element.

Here’s how you can do it:

1. Find the Element: Start by locating the element you’re interested in on the periodic table. Let’s use Carbon (C) as an example. Carbon has the atomic number 6.

2. Read the Atomic Mass: Look next to the symbol of the element. You will see a number that tells you its atomic mass. For Carbon, this number is about 12.01 amu, which stands for atomic mass units.

3. Know About Isotopes: Isotopes are different versions of an element that have different numbers of neutrons. For Carbon, the most common isotopes are Carbon-12 (written as $^{12}\text{C}$) and Carbon-13 (written as $^{13}\text{C}$).

4. Calculating the Average Atomic Mass: If you have the percentages of the isotopes, you can calculate the average atomic mass. The formula looks like this:

   $\text{Atomic mass} = ( \text{mass of } ^{12}C \times \text{percentage of } ^{12}C ) + ( \text{mass of } ^{13}C \times \text{percentage of } ^{13}C )$

   For example, if 98.89% of Carbon is Carbon-12 and 1.11% is Carbon-13, you would figure it out like this:

   $\text{Atomic mass} = (12 \times 0.9889) + (13 \times 0.0111)$

   This comes to about 12.01 amu, which is the same number you see on the periodic table.

By following these simple steps, you can find the atomic mass and understand why the periodic table is so important!