MODERN PERIODIC TABLE
☞VALENCY
Valency may be defined as “the combining capacity of the atom of an element with atoms of other elements in order to acquire the stable configuration (i.e. 8 electron in valence shell. In some special cases it is 2 electrons).”
☞ATOMIC SIZE
It refers to the distance between the centre of nucleus of an isolated atom to its outermost shell containing electrons.
The atomic radius decreases on moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.
In a group atomic size increases from top to bottom due to increase in number of shells.
METALLIC AND NON-METALLIC PROPERTIES
- In a period from left to right metallic nature decreases while non-metallic character increases.
- In a group metallic character increases from top to bottom while non-metallic character decrease.
☞ELECTRONEGATIVITY
The relative tendency of an atom to attract the shared pair of electrons towards itself is called electronegativity.
In a period from left to right, the value of electronegativity increases while in a group from top to bottom the value of electronegativity decreases.
☞IONIZATION ENERGY
The ionization energy (IE) is the amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation.
In a period from left to right, the value of ionization energy increases while in a group from top to bottom the value of ionization energy decreases.
☞ELECTRON AFFINITY
The electron affinity of an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.
In a period from left to right, the value of electron affinity increases while in a group from top to bottom the value of electron affinity decreases.
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