You already know that an atom is the smallest part of an element, and it is the basic building block of ordinary matter. But what exactly makes up an atom? In this activity, you will learn about the parts of an atom.

An atom is held together by forces of attraction between the electrons and the protons.

In atoms, the number of protons and electrons are equal.

 

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 Find oxygen on the table. It is in the non-metals section of the table. It is represented by the letter "O." Do you see the number 8 above oxygen? This tells you how many protons and electrons it has. This is true for all the elements on the periodic table. However, there are limits to how many electrons can be drawn on each circle around the nucleus.

You are going to deal with smaller atoms that have a maximum of three circles to be drawn around the nucleus. The first circle can hold two electrons, the second and third can hold eight each. Find chlorine, which is represented by "Cl" (it is also in the non-metal section of the table). What is the number above chlorine? Do you see that it is number 17?

This is how you would draw a picture of a chlorine atom. Do you see how the first (outside) circle contains 7 electrons, the next circle contains 8 electrons, and the most inner circle contains 2 electrons? This totals 17 electrons! Since the number of protons and electrons must be equal, you also know that there are 17 protons in the nucleus. It's that easy!

 

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