THE p-BLOCK ELEMENTS Ch7

THE p-BLOCK ELEMENTS Ch7

• The p-Block elements: P-block elements are those elements in groups

13 through 18 of the periodic table.• The ns2np1-6 valence shell electronic configuration is the defining feature of the p-block components' general electronic configuration.• Representative elements, also known as main group elements, are the elements that make up the s and p-blocks of the periodic table.

• Inert pair effect: As atomic size increases, the propensity of the ns2

electron pair to participate in bond formation reduces. As the atomic number rises within a group, the higher oxidation state's stability with regard to the lower oxidation state decreases. This pattern is known as the "inert pair effect." In other words, more energy is released during the formation of two new bonds than is needed to unpair the electrons.

APARTMENT 15 ELEMENTS

• Nitrogen group:

The elements of group 15 – nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and bismuth (Bi) belong to configuration is ns2np3.

Atomic and ionic radius: a) Radii get larger as you move along the group.

b) The covalent radii significantly rise from N to P.

c) Because heavy elements have fully filled d or f orbitals, there is a little

increase from As to Bi.

• Ionization energy: a) Due to an increase in atomic size, it continues to

decrease as you move down the group.

b) Because group 15 elements are smaller in size than group 14 elements,

group 15 elements have higher ionisation energies.

c) Group 15 elements have a more stable electronic configuration, such as

half-filled p-orbitals, than group 16 elements, which results in a greater ionisation energy.• All the elements in Group 15 exhibit allotropy, with the exception of nitrogen.

• Catenation: a) The triple bond in nitrogen causes some catenation,

while phosphorus exhibits catenation to the fullest. 1 / 3

b) Down the group, there is a decreasing probability to see catenation.

• Oxidation states: +3, +5, and -3 are the most prevalent oxidation states.

b) As atomic size increases, electronegativity diminishes, which leads to a

propensity for -3 oxidation states to appear lower in the group.

c) The inert pair effect causes the stability of the +5 oxidation state to

decline while the stability of the +3 oxidation state to rise.

d) The oxidation states of nitrogen range from -3 to +5.

e) In an acidic media, nitrogen and phosphorus atoms with oxidation

states ranging from +1 to +4 go through both oxidation and reduction.Disproportionation is the term for this action.

• Group 15 elements' reactivity towards hydrogen: a) MH3, all

trihydrides.

b) It is a component of sp3hybridization.

c) As bond dissociation energy drops down the group, the stability of

hydrides also diminishes.AsH3 > SbH3 > BiH3 > NH3 > PH3

 Boiling point:

PH3 < AsH3 < NH3 < SbH3 < BiH3

a) Boiling point increases with increase in size due to increase in van der

Waals forces.

b) Boiling point of NH3 is more because of hydrogen bonding.

 Bond angle:

NH3 (107.8°) > PH3 (99.5°) > AsH3 (91.8°) ≈ SbH3 (91.3°) > BiH3

(90°)

a) Electronegativity of N is highest. Therefore, the lone pairs will be

towards nitrogen and hence more repulsion between bond pairs.Therefore bond angle is the highest. After nitrogen, the electronegativity decreases down the group.

d) Basicity decreases as NH3 > PH3 > AsH3 > SbH3 < BiH3. This is

because the lone pair of electrons are concentrated more on nitrogen and hence the basicity will be maximum in the case of NH3. It will decrease down the group as the electronegativity 2 / 3

decreases down the group. The reducing power of hydrides increases down the group due to decrease in bond dissociation energy down the group.

• All group 15 elements, including trioxides (M2O3) and pentoxides, are reactive with oxygen. (M2O5).

b) As an oxide group descends, its basicity increases and its acidic

character declines. This is due to nitrogen's extremely small size.

c) It possesses a very modest yet potent positive field. As a result, it

quickly releases H+ ions and draws the electrons from the water O-H bond to itself.

d) Because atomic size grows as we advance down the group, the basicity

of oxide increases and its acidic nature diminishes.• Group 15 elements react with halogen to generate trihalides and pentahalides.

a) Trihalides

These are pyramid-shaped covalent compounds that undergo sp3 hybridization to become ionic down the group.

Pentahalides (B): Because they have open d-orbitals, they are Lewis acids.

They have sp3d hybridization, which gives them a trigonal biramidal form.

PCl5 is an ionic compound in the solid state and exists as [PCl][PCl].iv) PCl5 contains two axial bonds and three equatorial bonds. Due to stronger repulsion from equatorial bonds, the axial bonds are longer than equatorial ones.

v) Because there are no d- orbitals, nitrogen does not form pentahalides.

All elements react with metals to generate binary compounds in the -3 oxidation state.

• Nitrogen behaves abnormally:

 Anomalous behaviour of nitrogen:

The behaviour of nitrogen differs from rest of the

elements. Reasons:

• It has a small size.

ii. It does not have d – orbitals

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