The Periodic Table of Elements - Secondary 1 and 2

Each square of the periodic table corresponds to a chemical element. These squares contain important information about the element, such as: 

• its atomic number

• its name

• its chemical symbol

• its atomic mass

The colour of the square also generally gives information about the state of the element.

The information can be located in different parts of the square, depending on the periodic table. It is important to consult the legend of the table to find your way around.

Each element has its own number, known as its atomic number. The 118 elements of the periodic table are classified in ascending order of atomic number, from 1 to 118. The atomic number is assigned to each element according to the internal structure of its atoms.

In addition to having a unique atomic number, each element has a unique name, which is used to identify it in common vocabulary. The origin of these names varies greatly. Some names are given in honour of deities, scientists or places. For example, curium is named after twice Nobel Prize winner Marie Curie. Other names are given according to the properties of the elements. This is the case with iodine, which comes from the Greek word iodes, meaning violet, which is the colour of pure iodine^[2]. The name of the element can be different in different languages.

The chemical symbol consists of an uppercase letter, sometimes accompanied by a lowercase letter. The chemical symbol is derived from the Latin name of the element. It is the same in all languages. Often, it also corresponds to the first letters of the name in English, but this is not always the case. Hydrogen (H), helium (He), lithium (Li) and carbon (C) are examples of elements whose symbol corresponds to the first letters of their name. However, the word silver comes from the Old English word siolfur^[3]. Silver's chemical symbol is Ag.

The atomic mass of an element is the mass of a single atom of that element. Since the mass of an atom is extremely small, it is generally measured in atomic units (u) to simplify calculations. This is the unit used in the periodic table. One atomic unit corresponds roughly to the mass of hydrogen, the lightest chemical element.