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How to Read the Periodic Table
The Periodic table is designed to help you predict what an element's physical and
chemical properties are. You can also predict what elements will bond with each other.
First, let's look at the columns and rows of the periodic table.
Periodic Table Courtesy of Periodic Table of the Elements v. 4.0
by Kostas Tsigaridis (http://ptoe.move.to/)
Groups or Families
The vertical columns of the periodic table (there are 18) are called groups or families.
Elements in the same group or family have similar but not identical characteristics. You
will learn more about the 18 groups in a later section. You can know properties of a
certain element by knowing which group it belongs to.
Periods
The horizontal rows of the periodic table are called periods. Elements in a period are not
alike in properties. As a rule, the first element in a period is usually an active solid, and
the last element in a period is always an inactive gas. Atomic size decreases from left to
right across a period, but atomic mass increases from left to right across a period.
Atoms on the left of the period, therefore, are usually larger and more lightweight than
the smaller, heavier atoms on the right of the period.
Think Inside the Box
When you look at the periodic table, you should notice that each box represents a
different element, and each box contains vital information about the element, including
its name, symbol, atomic number, and atomic mass. Look at the sample box below for a
description of each of these pieces of information.
6
C
Carbon
12.011
The top number is the atomic number. Every element has its own unique atomic
number. The atomic number tells how many protons are in one atom of that element.
Since no two elements have the same atomic number, no two elements have the same
number of protons. In neutral (electric charge 0) atoms, the number of protons is equal
to the number of electrons. Thus, in neutral atoms, the atomic number also represents
the number of electrons of this atom
The large letter is the element's symbol, and just below that is the element's name.
Each element has its own unique symbol and name. It is often very useful to memorize
symbols and names for elements, especially the more commonly used elements.
Below the name is the element's atomic mass. The atomic mass is the mass in atomic
mass units for all possible isotopes of that element. The atomic mass essentially gives
you an estimate of how massive one atom of that element is.
You can use the atomic mass and the atomic number to calculate the number of
neutrons present inside the nucleus of the most common atom of any element. To do
this take the atomic mass and subtract the atomic number, and the answer is the
number of neutrons. For example, Carbon's atomic mass equals 12.011 amu, and its
atomic number is 6. The number of neutrons that Carbon has is then 12.011 (atomic
mass) – 6 (atomic number) = 6.011 → and because you cannot have 6.011 neutrons,
we round to the nearest whole number, which gives us 6 neutrons. So, the most
common Carbon atom has 6 neutrons.
Adapted from D. Gibson http://web.buddyproject.org/web017/web017/pertab.html