The modern periodic table contains 18 vertical columns known as groups.
Group 1 elements are known as alkali metals.
Group 2 elements are known as alkaline earth metals.
Group 15 elements are known as pnicogens.
Group 16 elements are known as chalcogens.
Group 17 elements are known as halogens.
Group 18 elements are known as noble gases.
Alkali Metals
The elements in the first group, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr) are called alkali metals.
They were given the name because they all react with water to form alkalis.
The alkali metals are all shiny, soft, highly reactive solids at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1.
Number of valence electrons = 1
Alkali Earth Metals
The elements in the second group, beryllium(Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) are called alkaline earth metals.
They were given the name because their oxides are alkaline in nature.
They are all shiny, silvery-white, somewhat reactive hard solids at standard temperature and pressure. They lose two electrons from their outermost shell to form cations with charge +2.
Number of valence electrons = 2
Halogens
The elements in the seventeenth group (F, Cl, Br, I and As) are called halogens and exist as diatomic molecules. The symbol ‘X’ is often used generically to refer to any halogen.
They were given the name halogen, from the Greek words, Hal (“salt”) and gen (“to produce”), because they all produce a wide range of salts on reacting with metals.
The halogens exist at room temperature in all three states of matter: Solid – Iodine, Astatine. Liquid – Bromine. Gas – Fluorine, Chlorine.
Number of valence electrons = 7
Noble Gases
The elements in the eighteenth group, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn) are called noble gases.
They are all odourless, colourless and monatomic gases with very low chemical reactivity.
Since their valence shell is considered to be “full”, they have little tendency to participate in chemical reactions.
When discovered and identified, scientists thought they are exceedingly rare, as well as chemically inert, and therefore these gases were also given the names ‘rare’ or ‘inert’ gases.
Number of valence electrons = 8
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