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.
Groups or Families
The 18 vertical (up & down) columns of the periodic table are called groups or families. Elements in the same
group or family have similar but not identical characteristics. You can know properties of a certain element by
knowing which group it belongs to.
Periods
The horizontal (side to side) 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 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 atomic
number which 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.
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.
Below the name is the element's atomic mass. The atomic mass
essentially gives you an estimate of how massive one atom of that element
is.
Elements vs. Compounds
Elements are substances that cannot be separated into simpler substances.
The smallest particles of matter are called atoms. Remember the carrot from the other chapter. If
you continue to chop a carrot into smaller and smaller pieces, eventually you would reach a
point where you could not cut up the carrot anymore, but still have carrot. You would then have
molecules of carrot. The same applies to elements. If you continually cut up a piece of
aluminum, you will reach a point that you could no longer divide it. These are aluminum atoms.
An atom is the smallest particle of an element that has the properties of that element. Some
properties of aluminum are: shiny, silver colored, fragile, and thin. Each element has its own type
of properties.
Chemists use symbols to represent elements. A symbol is a letter or picture used to represent
something. Chemists use letters to represent elements. The symbol for aluminum is Al.
The symbol for oxygen is O.
Compounds
A compound is a substance formed when two or more elements are chemically joined. Because
compounds are made more than one element it is possible to break them down into their
separate elements. Water, salt, and sugar are examples of compounds. Salt is made up of the
elements sodium and chloride. Water is made up of the elements hydrogen and oxygen. Sugar
is a combination of hydrogen, carbon, and oxygen. When the elements are joined, the atoms
lose their individual properties and have different properties from the elements they are
composed of. For example, carbon is basically charcoal and hydrogen and oxygen are clear
gases. When they chemically combine in the right way they form sugar… which is nothing like
its separate ingredients!