# What is The Periodic Table of Elements?

Reviewed by on Dec 27, 2006
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Kidzworld tells you what the Periodic Table of Elements is about, how to read this chart and all about the element groups. - Page 1

We've discussed chemistry and we've mentioned the Periodic Table of Elements but we didn't go into a lot of detail about the periodic chart. Here's what you've always wanted to know about the Periodic Table of Elements and what you've been too lazy to ask your science teacher.

## What IS the Periodic Table of elements?

The periodic chart is like the bible of chemistry. It's the most important reference in chemistry because it arranges all the elements in an easy to read chart. Elements are placed in order of increasing atomic number, from left to right and top to bottom. The different rows of elements are called periods.

Anyone using the Periodic Table can find out exactly what they need to know about an element. For example, a teacher can use carbon's atomic mass to find out how many carbon atoms there are in a 1 kilogram block of carbon. The layout of the elements also says a lot about each element. Elements found in the same column of the Periodic Table (known as a group) have identical electron configurations (the locations of the electrons in an unexcited atom) and behave pretty much the same way chemically. An example of this is group 18 elements which are all noble gases. (Keep readin' if you aren't sure what group 18 elements are - we'll explain it further down.) So even if you don't know anything about an element, it's not hard to get the 411 if you read the periodic chart.

## How Do I Read the Chart?

Each element is represented by a letter (or two) and some numbers in the box. This basic info tells a lot about that element. Here's how you read the element - the number on top is the atomic number, the letter(s) in the box are the atomic symbol and the number on the bottom is the atomic mass.

Atomic Number - An element is defined by the number of protons in it. Carbon atoms have six protons, hydrogen atoms have one proton and oxygen atoms have eight protons. The number of protons an atom has is called the atomic number. The chemical behavior of an element depends on the number of protons in an atom.
Atomic Symbol - These are almost always one or two letters that represent an element. They're used worldwide and usually relate to the name of the element or the Latin name of the element. An example of this is "O" for Oxygen and "Ca" for Calcium.
Atomic Mass - The average mass of an element in atomic mass units (amu.) The mass in an atom is so small that we use amu. That's about the mass of one proton or neutron. The atomic mass is a decimal number on the Periodic Table because it's an average of the various isotopes (one or more atoms that have the same atomic number but different mass numbers) of an element. To find the average number of neutrons for an element, simply subtract the number of protons (atomic number) from that atomic mass.