Periodic Properties

Sreenandu

Jr. Faculty for Chemistry

Periodic Properties

Properties which repeat at regular intervals periodic properties

Atomic radius

Ionic radius

Ionization enthalpy

Electron gain enthalpy

Electro negativity

valency

Atomic radius

• ‘ it is the distance from the center of the nucleus to the outermost shell of electrons’

Periodic trend of atomic radius

Ionic radius

Isoelectronic species

Ionization enthalpy• ‘Minimum amount of energy required to remove the most loosely bound

electron from an isolated gaseous atom’

• Unit – kJ mol-1

Factors affecting IE

Factors affecting IE

Change Effect on IE Remark

Atomic size Increases decreases Nuclear attraction decreases

Nuclear chargePositive increases Nuclear attraction increases

negative Low IE Nuclear attraction decreases

Screening or shielding effect

No. of inner

electron increases

IE decreases

Inner electron shield outer electron from nuclear attraction

Half or completelyfilled orbitals

increases Extra stabilityEg IE of N > O

Type of subshell Order of energy to remove electrons > p > d > f

IE

Electron gain enthalpy

‘Amount of energy released when an electron is added to an atom’

Factors affecting Change Effect on Electron gain

enthapy

Remark

Atomic size Increases low Nuclear attraction decreases

Nuclear chargePositive high Nuclear attraction increases

negative low Nuclear attraction decreases

Variation along a period left to right more negative

( Be, N and noble gases have positive)

Variation ina group less negative ( but Cl has more than F)

Electronegativity

‘It is the tendency to attract shared pair of electrons towards it’.

Depends onFactors affecting Change Effect on Electronegativity

Remark

Atomic size Increases low Nuclear attraction decreases

Nuclear chargePositive high Nuclear attraction increases

negative low Nuclear attraction decreases

Periodic trend of chemical properties

• Valency / oxidation state

• Metallic character

• Reducing character

• Oxidizing character

Valency

“the combining power of an element, especially asmeasured by the number of hydrogen atoms it candisplace or combinewith”

Or it is the number of electrons gaining or losing tomake bonds

Metallic character

• Tendency to become electropositive

• Decreases from left to right

• Increases from top to bottom

Therefore, 1st group elements will have

more metallic character( Alkali metals)

Reducing character

• They provide electrons

• Thus metal act as good reducing agents

• Reducing character decreases across the period

• It increases down the group

• Alkali metals are very good reducing agents

Oxidizing character

• They accept electrons

• Non metals are good oxidizing agents

• Oxidizing character increases across the period

• Decreases down the group

• Halogens are very good oxidizing agents

Summary