STD X – PERIODIC TABLE, PERIODIC PROPERTY, VARIATION IN PROPERTY – EINSTEIN

Periodic Table

Periodic properties and their variations in groups and periods.

Definitions and trends of the following periodic properties in groups and periods will be studied:

atomic size

metallic character

non-metallic character

ionisation potential

electron affinity

electronegativity

 Periodicity on the basis of atomic number for elements.

The study of modern periodic table up to period 3 (students to be exposed to the complete modern periodic table but no questions will be asked on elements

beyond period 3 – Argon);

Periodicity and other related properties

will be explained on the basis of nuclear charge and shells (not orbitals). (Special reference to the alkali metals and h

Law of Octaves

Every eighth element (starting from any given element) has properties similar to the first element, in the same pattern as seen in musical notes. The first note ‘sa’ repeats itself after every 7 notes thus showing the similarity between periodicity and musical note pattern.

This law gave the first idea about periodicity present in elements.

Once the rare gases were discovered, it could not explain the similarity between the first and eighth elements.

Long form of periodic table

Valency increases from 1-4 and then decreases from 4-0 across the period.

Valency remains the same down the group.

Ionisation potential increases down the group.

Atomic size increases down the group due to addition of a new shell.

Electron affinity decreases down the group.

Metallic nature and basic nature of oxides decreases across the period.