chemistry

CLASSIFICATION OF ELEMENTS INTO 4 TYPES

This is based on properties of elements.

Elements are further classified as

1)  Inert gases

2)  Representative elements

3)  Transition elements

4)  Inner transition elements.

INERT GASES :

Inert gas elements have all completed shells. They belong to '0' group in the periodic table.

Helium, Neon, Argon, Krypton, Xenon, Radon are called noble gases or rare gases or inert gases (or) aerogens

These are monoatomic gases. They are chemically inactive.

They are placed at the extreme right of the periodic table.

REPRESENTATIVE ELEMENTS:

s-block or p-block elements except '0' group are called representative elements. They have only one incomplete outer shell.

These elements attain the nearest inert gas configuration by losing or gaining or sharing electrons. They are chemically active.

A few metals and metalloids are found in representative elements.

Because of their reactivity and frequent occurrence they are called representative elements. They include most reactive metals and most reactive non-metals.

TRANSITION ELEMENTS:

These are d-block elements.

They have two incomplete outer shells ultimate and penultimate.

Their general electronic configuration is (n – 1)d^1–10ns^1–2.

Neutral atoms or Ions having incomplete d-orbitals are called transition elements.

Zn, Cd and Hg are not considered to be transition elements as their atoms and Ions have completed d-orbitals.

Small atomic size, high nuclear charge, and unpaired d-electrons give characteristic properties to transition elements.

Transition elements are hard and dense metals. They have high melting and boiling points.

They are good conductors of heat and electricity. They show variable oxidation states.

They form coloured compounds.

They form complexes or co-ordinate covalent compounds.

They readily form alloys like brass, bronze, german silver etc.

INNER TRANSITION ELEMENTS:

The f-block elements are called inner transition elements as they bring about transition among transition metals.

The differentiating electron enters into the f-orbital of anti penultimate shell.

These elements have three incomplete outer shells.

The general electronic configuration of these elements is (n – 2)f^1–14(n – 1)d^0–1ns².

These elements show similar properties due to the similar electronic configuration in the last two shells.

They exhibit the common oxidation state + 3.

All the inner transition elements belong to the same group (i.e. IIIB)