The Periodic Table

The Periodic Table is arranged in order of Groups and Periods.

(a) Group

The groups in the Periodic Table are numbered from I to VII and then Group 0. Some of these groups have names:

Group I: Alkali Metals

Group II: Alkaline Earth Metals

Group VII: Halogens

Group 0: Noble Gases

Elements between Group II and III are known as transition metals or transition elements.

Elements in the same group have similar chemical properties and will undergo the same type of chemical reactions.

(b) Period

Each period is numbered. Elements in the 1st period will only have their 1st shell either partially or fully occupied with electrons.

Elements in the 2st period will have their 1st shell fully occupied with electrons, and their 2nd shell fully or partially equipped with electrons.

Periodic Table Overview

The periodic table shows all the elements arranged in order of increasing atomic number.

(i) Electronic structure

Down each group, the number of valence electrons is the same for each element and is equal to the group number. For example, in Group I elements, we have:

Li - 2.1

Na - 2.8.1

K - 2.8.8.1

As Group I elements are very reactive, and elements with similar electronic configurations (similar number of valence electrons) have similar chemical properties, elements in the same group have similar chemical properties.

(ii) Metals and non-metals

Across the period, the properties of elements change from metallic to non-metallic.

The elements in blue are metals, the elements in yellow are non-metals and the elements in purple are metalloids. Metalloids have some properties of metals and non-metals, thus they are neither metal nor non-metal.

Order of reactive metals:

Practically all the elements after Hydrogen do not react with acids to give hydrogen gas and are the least easily corroded.