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p-Block Elements: one-page cheat sheet

NEET Chemistry · Unit 10 · Inorganic Chemistry

ScoreChemby CSJ Sir
Weightage: 3–4 questions · 12–16 marks

1 · Group 13 (boron family)

Inert pair+1 gains stability down the group: Tl

^{+} >

^{3 +}

, so TlI

>

TlI

_{3}

BF_{3} < BCl_{3} < BBr_{3} < BI_{3} (Lewis acidity)

Back-bonding ( $2 p π$ – $2 p π$ ) is strongest in BF $_{3}$ , so it is the weakest acid.

DiboraneB

_{2}

_{6}

: two 3c–2e bridges, four 2c–2e terminal bonds, B is

s p^{3}

Boric acidB(OH)

_{3}

+ 2H

_{2}

\to

[B(OH)

_{4}

]

^{-}

+ H

_{3}

^{+}

(Lewis acid, not a proton donor)

Othersborax Na

_{2}

_{4}

_{7} \cdot

10H

_{2}

O; borazine B

_{3}

_{3}

_{6}

2 · Group 14 (carbon family)

C ≫ Si > Ge \approx Sn ≫ Pb (catenation)

Allotropesdiamond

s p^{3}

; graphite

s p^{2}

; fullerene C

_{60}

s p^{2}

Inert pairPbCl

_{2}

is stable, PbCl

_{4}

is not

CovalencyC max 4; Si can reach 6 (SiF

_{6}^{2 -}

) using

d

-orbitals

Silicones(R

_{2}

SiO)

_{n}

from R

_{2}

SiCl

_{2}

hydrolysis

CObinds Hb about 300 times more strongly than O

_{2}

3 · Group 15 (nitrogen family)

Nonly

2 s, 2 p

: no

d π

–

p π

bonding; forms

p π

–

p π

\equiv

NH_{3} > PH_{3} > AsH_{3} > SbH_{3} > BiH_{3} (stability, basicity)

Boiling point: NH $_{3}$ highest (H-bonding), then SbH $_{3} >$ AsH $_{3} >$ PH $_{3}$ .

Acid	O.S.	Basicity	P–H
H $_{3}$ PO $_{2}$	+1	1	2
H $_{3}$ PO $_{3}$	+3	2	1
H $_{3}$ PO $_{4}$	+5	3	0
H $_{4}$ P $_{2}$ O $_{7}$	+5	4	0

Only those with P–H bonds (H $_{3}$ PO $_{2}$ , H $_{3}$ PO $_{3}$ ) are reducing.

4 · Phosphorus halides with ROH

3 ROH + PCl_{3} \to 3 RCl + H_{3} PO_{3}

ROH + PCl_{5} \to RCl + POCl_{3} + HCl

5 · Group 16 (oxygen family)

O states

- 2

;

- 1

_{2}

_{2}

);

+ 1

_{2}

_{2}

);

+ 2

(OF

_{2}

)

Hydridesacidity H

_{2}

<

_{2}

<

_{2}

<

_{2}

Te; bp H

_{2}

<

_{2}

<

_{2}

<

_{2}

_{3}

bent, diamagnetic; oxidises I

^{-}

to I

_{2}

Oxoacid	Formula	Feature
Sulphurous	H $_{2}$ SO $_{3}$	S–OH ×2, S=O ×1
Sulphuric	H $_{2}$ SO $_{4}$	S–OH ×2, S=O ×2
Pyrosulphuric	H $_{2}$ S $_{2}$ O $_{7}$	S–O–S bridge
Peroxodisulphuric	H $_{2}$ S $_{2}$ O $_{8}$	S–O–O–S bridge

Contact process: SO $_{2}$ $\to$ SO $_{3}$ over V $_{2}$ O $_{5}$ ; SO $_{3}$ in H $_{2}$ SO $_{4}$ gives oleum.

6 · Group 17 (halogens)

F_{2} > Cl_{2} > Br_{2} > I_{2} (oxidising power)

Bond enthalpyCl

_{2} >

_{2} >

_{2} >

_{2}

Hydridesacidity HF

<

HCl

<

HBr

<

HI; bp HF highest

OxoacidsHOCl

<

HClO

_{2}

<

HClO

_{3}

<

HClO

_{4}

(acid strength)

Cold dil. NaOHX

_{2}

\to

^{-}

+ OX

^{-}

Hot conc. NaOHX

_{2}

\to

^{-}

+ XO

_{3}^{-}

ShapesClF

_{3}

T-shaped (

s p^{3} d

, 2 lp); BrF

_{5}

square pyramidal; IF

_{7}

pentagonal bipyramidal

7 · Group 18 (noble gases)

BartlettXe + PtF

_{6}

\to

^{+}

[PtF

_{6}

]

^{-}

Species	lp	Hybrid.	Shape
XeF $_{2}$	3	$s p^{3} d$	linear
XeF $_{4}$	2	$s p^{3} d^{2}$	square planar
XeF $_{6}$	1	$s p^{3} d^{3}$	distorted octahedral
XeO $_{3}$	1	$s p^{3}$	pyramidal
XeOF $_{4}$	1	$s p^{3} d^{2}$	square pyramidal

XeF_{6} + 3 H_{2} O \to XeO_{3} + 6 HF

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Stability: TlCl $_{3}$ vs TlCl, InI $_{3}$ vs InI, TlI vs TlI $_{3}$ ?

Inert pair: Tl $^{+}$ is more stable than Tl $^{3 +}$ , so TlI $>$ TlI $_{3}$ .

8 · Nitrogen chemistry

HaberN

_{2}

+ 3H

_{2}

⇌

2NH

_{3}

(Fe, about 700 K, 200 atm)

Ostwald4NH

_{3}

+ 5O

_{2}

\to

4NO + 6H

_{2}

O (Pt/Rh)

2NO + O

_{2}

\to

2NO

_{2}

; 3NO

_{2}

+ H

_{2}

\to

2HNO

_{3}

+ NO

Cu + HNO

_{3}

conc. gives NO

_{2}

; dilute gives NO

PCl

_{5}

solid is [PCl

_{4}

]

^{+}

[PCl

_{6}

]

^{-}

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ClF $_{3}$ : Cl has 3 bond pairs and 2 lone pairs ( $s p^{3} d$ ).

Lone pairs sit equatorial, so the shape is bent T-shaped.

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Diborane: each B is $s p^{3}$ . Two $s p^{3}$ orbitals make terminal 2c–2e bonds, two make bridge 3c–2e bonds.

Six traps to remember

Oxygen is not always $- 2$ : $+ 2$ in OF $_{2}$ , $+ 1$ in O $_{2}$ F $_{2}$ , $- 1$ in peroxides.
Nitrogen cannot form $d π$ – $p π$ bonds: it has no $d$ -orbitals.
Boron in diborane is $s p^{3}$ , not $s p^{2}$ .
BF $_{3}$ is the weakest Lewis acid of the boron trihalides.
PCl $_{3}$ + ROH gives H $_{3}$ PO $_{3}$ ; PCl $_{5}$ + ROH gives POCl $_{3}$ .
Carboxyhaemoglobin is about 300 times more stable than oxyhaemoglobin.

p-Block Elements: free one-page cheat sheet

1 · Group 13 (boron family)

2 · Group 14 (carbon family)

3 · Group 15 (nitrogen family)

4 · Phosphorus halides with ROH

5 · Group 16 (oxygen family)

6 · Group 17 (halogens)

7 · Group 18 (noble gases)

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8 · Nitrogen chemistry

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Six traps to remember