The p-Block Elements Formula Sheet — NEET Chemistry

Every key The p-Block Elements formula, definition and fact for NEET Chemistry in one place — with common examiner traps and worked examples. Free to read; blurt from memory, then check your gaps.

Syllabus — topics coveredNCERT · 5 sub-topics

General introduction; electronic configuration and trends (Groups 13-18)
Anomalous behaviour of the first element of each group
Group 13 and 14 — properties and important compounds
Group 15, 16, 17 and 18 — properties and important compounds
Uses of p-block elements and their compounds

p-Block: General Introduction & Trends

The p-block (Groups 13–18): Elements whose last electron enters a p orbital — valence configuration

n s^{2} n p^{1 - 6}

(He is

1 s^{2}

). The block uniquely contains

metals, metalloids and non-metals

; non-metallic character decreases down each group.

Group	Valence config	2nd-period element	Group oxid. state
13	$n s^{2} n p^{1}$	B	+3
14	$n s^{2} n p^{2}$	C	+4
15	$n s^{2} n p^{3}$	N	+5
16	$n s^{2} n p^{4}$	O	+6
17	$n s^{2} n p^{5}$	F	+7
18	$n s^{2} n p^{6}$	Ne	+8 (—)

Gr 13 / 14 / 15

+ 3 / + 4 / + 5

Gr 16 / 17 / 18

+ 6 / + 7 / + 8

★ Remember · Inert pair effect

Down a group the

n s^{2}

pair becomes reluctant to bond (poor d/f shielding), so the

lower

(group

- 2

) oxidation state grows more stable:

T l^{+} > T l^{3 +}

P b^{2 +} > P b^{4 +}

B i^{3 +} > B i^{5 +}

🎯 Exam · Anomalous first member

B, C, N, O, F differ from heavier members:

small size

, high electronegativity,

no d -orbitals

(max covalence 4), and strong

p π

–

p π

multiple bonding (e.g.

N \equiv N

O = O

) that the heavier elements lack.

Oxide & character trends

▸Across a period: metallic $↓$ , non-metallic $↑$ ; oxides go $basic \to amphoteric \to acidic$ .
▸Down a group: metallic character $↑$ , so oxides become more basic.
▸Non-metals form acidic (or neutral) oxides; metals form basic oxides.

🚫 Examiner Trap · Examiner traps

(1)

Inert pair effect

: down a group the LOWER (group

- 2

) oxidation state grows more stable (Tl

^{+}

, P

b^{2 +}

, B

i^{3 +}

). (2) The 1st member (B, C, N, O, F) is anomalous — small,

no d

-orbital (max covalence 4), strong

p π

–

p π

bonding. (3) Oxides across a period: basic

\to

amphoteric

\to

acidic. (4) The p-block uniquely has metals, metalloids AND non-metals.

Group 13 — Boron Family

Trends (

n s^{2} n p^{1}

)

▸B is a $non-metal$ (hard, high m.p.); Al, Ga, In, Tl are metals.
▸Atomic radius: Ga $(135) <$ Al $(143)$ pm — poor $d$ -electron shielding.
▸ $Inert pair$ : $+ 1$ stability rises Al $< G a < I n <$ Tl, so $T l^{+}$ is stable and $T l^{3 +}$ is strongly oxidising.
▸Trihalides are $electron-deficient Lewis acids$ ( $B F_{3} + : N H_{3} \to F_{3} B \leftarrow N H_{3}$ ).

Diborane B2H6 with four terminal two-centre-two-electron B-H bonds and two bridging three-centre-two-electron banana bonds, beside the chlorine-bridged Al2Cl6 dimer — Diborane's two bridging H use 3c–2e 'banana' bonds; $A l_{2} C l_{6}$ bridges similarly.

Key boron compounds:

Borax

N a_{2} B_{4} O_{7} \cdot 10 H_{2} O

(alkaline solution; borax-bead test).

Orthoboric acid

H_{3} B O_{3}

— a weak

monobasic Lewis acid

(

B (OH)_{3} + H_{2} O \to [B (OH)_{4}]^{-} + H^{+}

), layered, H-bonded.

Diborane

B_{2} H_{6}

— catches fire in air, hydrolyses to

H_{3} B O_{3}

🎯 Exam · Aluminium is amphoteric

Al dissolves in both acid and alkali liberating

H_{2}

2Al + 6HCl \to 2AlC l_{3} + 3 H_{2}

and

2Al + 2NaOH + 6 H_{2} O \to 2Na [Al (OH)_{4}] + 3 H_{2}

. Oxides go

B_{2} O_{3}

(acidic)

\to A l_{2} O_{3}

(amphoteric)

\to T l_{2} O_{3}

(basic).

🚫 Examiner Trap · Examiner traps

(1) B is a

non-metal

; Al–Tl are metals. (2) Ga

(135) <

(143)

pm — poor d-shielding anomaly. (3) Diborane has

4 terminal 2c-2e

+

2 bridge 3c-2e

(banana) bonds — B is electron-deficient. (4)

H_{3} B O_{3}

is a weak

monobasic Lewis acid

(accepts OH

^{-}

), not a proton donor; Al and its oxide are amphoteric.

Group 14 — Carbon Family

Trends (

n s^{2} n p^{2}

)

▸C (non-metal), Si (non-metal), Ge (metalloid), Sn & Pb (metals).
▸ $Catenation$ (self-linking) falls C $≫$ Si $>$ Ge $\approx$ Sn; Pb shows none.
▸Only carbon forms strong $p π$ – $p π$ multiple bonds (C=C, C=O, C≡N).
▸Oxidation $+ 4$ and $+ 2$ ; $+ 2$ stability rises Ge $< S n <$ Pb (inert pair), so $P b^{2 +}$ is stable, $P b^{4 +}$ oxidising.

Bar chart of E-E bond enthalpies showing C-C 348 greater than Si-Si 297 greater than Ge-Ge 260 and Sn-Sn 240, beside Group 14 highlights on allotropes and oxides — Falling E–E bond enthalpy explains the catenation order.

Oxides & allotropes:

Oxides

: CO neutral,

C O_{2}

Si O_{2}

acidic,

Sn O_{2}

Pb O_{2}

amphoteric.

C O_{2}

is a discrete linear

O = C = O

molecule, but

Si O_{2}

is a giant covalent network.

Carbon allotropes

: diamond (

s p^{3}

, 3-D), graphite (

s p^{2}

layers, conducting), fullerene (

C_{60}

⚠️ Watch out · Why

CC l_{4}

resists hydrolysis but

SiC l_{4}

doesn't

SiC l_{4}

hydrolyses (

\to Si (OH)_{4}

) because Si can use vacant

3 d

orbitals to accept the water lone pair; carbon has

no d -orbital

, so

CC l_{4}

is inert to water.

🚫 Examiner Trap · Examiner traps

(1) Catenation falls C

≫

>

\approx

Sn (Pb none) — tracks E–E bond enthalpy. (2) Only C forms strong

p π

–

p π

bonds (C

=

C, C

=

O). (3) CC

l_{4}

resists hydrolysis (C has no d-orbital); SiC

l_{4}

hydrolyses (Si uses

3 d

). (4)

+ 2

stability rises Ge

< S n <

Pb (inert pair)

\Rightarrow

b^{4 +}

is oxidising.

Group 15 — Nitrogen Family

Trends (

n s^{2} n p^{3}

)

▸Half-filled $n p^{3}$ gives extra stability and high ionization enthalpy.
▸Oxidation states $- 3, + 3, + 5$ ; $- 3$ tendency falls and $+ 3$ (inert pair, Bi) rises down the group.
▸ $Hydrides$ $E H_{3}$ : stability & basicity fall $N H_{3} > P H_{3} > As H_{3} > Sb H_{3} \geq Bi H_{3}$ ; reducing power rises the opposite way.
▸Anomalous N: $N \equiv N$ triple bond, no d-orbital, max covalence 4 (no $NC l_{5}$ ).

Structures of N2O linear, NO2 angular, the trigonal pyramidal ammonia molecule, and a ladder of nitrogen oxidation states from minus 3 to plus 5 — Nitrogen's oxidation states $- 3$ to $+ 5$ and key molecular shapes.

Ammonia & nitric acid:

NH_{3}

— trigonal pyramidal, made by Haber's process (

N_{2} + 3 H_{2} ⇌ 2N H_{3}

, Fe, ~700 K, 200 atm); a Lewis base forming complexes (deep-blue

[Cu (N H_{3})_{4}]^{2 +}

HNO_{3}

— Ostwald process (

4N H_{3} + 5 O_{2} Pt/Rh 4NO

); a strong oxidiser that passivates Al, Cr, Fe.

🎯 Exam · Phosphorus essentials

Allotropes:

white

P_{4}

(reactive, tetrahedral

6 0^{\circ}

, glows),

red

(polymeric, stable),

black

. Halides:

PC l_{3}

pyramidal (

s p^{3}

);

PC l_{5}

trigonal bipyramidal (solid is ionic

[PC l_{4}]^{+} [PC l_{6}]^{-}

). Oxoacid basicity = number of P–OH bonds (

H_{3} P O_{2}

mono,

H_{3} P O_{3}

di,

H_{3} P O_{4}

tri).

🚫 Examiner Trap · Examiner traps

(1) Hydride stability/basicity fall NH

_{3} >

_{3} >

AsH

_{3} >

SbH

_{3} >

H_{3}

; reducing power rises the OPPOSITE way. (2) N has no d-orbital

\Rightarrow

max covalence 4 (no NC

l_{5}

); it forms the N

\equiv

N triple bond. (3) PC

l_{5}

solid is ionic [PC

l_{4}]^{+} [PC l_{6}]^{-}

. (4) Oxoacid basicity

=

number of

P-OH

bonds (

H_{3} P O_{2}

mono,

H_{3} P O_{3}

di,

H_{3} P O_{4}

tri).

Group 16 — Oxygen Family

Trends (

n s^{2} n p^{4}

, chalcogens)

▸O & S non-metals, Se & Te metalloids, Po metal; oxidation $- 2, + 2, + 4, + 6$ .
▸ $Hydrides$ $H_{2} E$ : acidity rises $H_{2} O < H_{2} S < H_{2} Se < H_{2} Te$ ; thermal stability falls down the group.
▸Anomalous O: small size & H-bonding make $H_{2} O$ a liquid (vs gaseous $H_{2} S$ ).
▸ $O_{2}$ is paramagnetic; $O_{3}$ (ozone) is bent and a powerful oxidiser.

The bent O_3 molecule and the puckered S_8 ring. — The bent $O_{3}$ molecule and the puckered $S_{8}$ ring.

Sulphur & its oxides:

Allotropes

: rhombic (

α

) and monoclinic (

β

) sulphur, both built of puckered

S_{8}

crown rings.

S O_{2}

is angular and a

reducing agent

(decolourises acidified

KMn O_{4}

). Oxides classify as acidic (

S O_{3}

), basic (

N a_{2} O

), amphoteric (

A l_{2} O_{3}

) or neutral (CO, NO).

★ Remember ·

H_{2} S O_{4}

— Contact process

S \to S O_{2}

;

2S O_{2} + O_{2} V_{2} O_{5} 2S O_{3}

;

S O_{3} + H_{2} S O_{4} \to H_{2} S_{2} O_{7}

(oleum); dilute to

H_{2} S O_{4}

. It is a strong acid,

dehydrating

agent (

C_{12} H_{22} O_{11} \to 12C

) and (hot, conc.) an oxidiser.

🚫 Examiner Trap · Examiner traps

(1) Hydride

acidity

rises

H_{2}

<

H_{2}

<

H_{2}

<

H_{2}

Te, but thermal

stability

falls. (2)

H_{2}

O is a liquid (H-bonding) while

H_{2}

S is a gas — O's anomaly. (3) S

O_{2}

is a REDUCING agent (decolourises KMn

O_{4}

);

O_{3}

is an oxidiser. (4) Contact process uses

V_{2} O_{5}

; conc.

H_{2} S O_{4}

is a dehydrating agent.

Group 17 — Halogens

Trends (

n s^{2} n p^{5}

)

▸Most reactive non-metals; oxidising power $F_{2} > C l_{2} > B r_{2} > I_{2}$ .
▸Oxidation $- 1$ (only state for F); Cl, Br, I also show $+ 1, + 3, + 5, + 7$ .
▸Anomalous F: small, no d-orbitals, low F–F bond energy; $Δ_{e g} H$ of Cl is more negative than F.
▸A halogen oxidises the halide of a higher member ( $C l_{2} + 2B r^{-} \to 2C l^{-} + B r_{2}$ ).

Interhalogen shapes: ClF_3 (T-shaped), BrF_5 (square pyramidal), IF_7 (pentagonal bipyramidal). — Interhalogen shapes: $Cl F_{3}$ (T-shaped), $Br F_{5}$ (square pyramidal), $I F_{7}$ (pentagonal bipyramidal).

Hydrogen halides & chlorine:

HX acidity

rises

HF < HCl < HBr < HI

(bond strength falls the other way); HF is a liquid (H-bonding).

C l_{2}

Mn O_{2} + 4HCl \to MnC l_{2} + C l_{2} + 2 H_{2} O

; with dry slaked lime gives

bleaching powder

Ca (OCl) Cl

🎯 Exam · Interhalogens & oxoacids

Interhalogens

X X_{n}^{'}

are more reactive than the halogens:

X X_{3}^{'}

bent T-shape (

Cl F_{3}

X X_{5}^{'}

square pyramidal (

Br F_{5}

X X_{7}^{'}

pentagonal bipyramidal (

I F_{7}

). Oxoacid strength rises with O atoms:

HOCl < HCl O_{2} < HCl O_{3} < HCl O_{4}

🚫 Examiner Trap · Examiner traps

(1) Oxidising power F

_{2} >

_{2} >

_{2} >

I_{2}

; a halogen displaces the halide below it. (2) HX acidity rises HF

<

HCl

<

HBr

<

HI (bond strength falls). (3) F shows

only

- 1

(no d-orbital);

Δ_{e g} H

of Cl is more negative than F. (4) Oxoacid strength rises with O count: HOCl

<

HClO

_{2} <

HClO

_{3} <

HCl

O_{4}

Group 18 — Noble Gases

Trends (

n s^{2} n p^{6}

)

▸Completely filled valence shells $\Rightarrow$ very high IE, positive $Δ_{e g} H$ , chemical inertness.
▸Monatomic gases; only weak dispersion forces give $very low$ boiling points (He = 4.2 K, lowest of all).
▸Atomic radius and reactivity increase down the group.
▸Only the heavier, larger Xe (and some Kr) form compounds — with the most electronegative F and O.

Xenon fluorides by VSEPR: XeF2 linear, XeF4 square planar, XeF6 distorted octahedral, with hydrolysis to XeO3 and uses of helium, neon and argon — Xenon fluoride shapes (VSEPR), hydrolysis and noble-gas uses.

Xenon compounds: First made after Bartlett (1962) prepared

X e^{+} [Pt F_{6}]^{-}

Xe F_{2}

linear,

Xe F_{4}

square planar,

Xe F_{6}

distorted octahedral. Hydrolysis:

Xe F_{6} + 3 H_{2} O \to Xe O_{3} + 6HF

(

Xe O_{3}

pyramidal); partial hydrolysis gives

XeO F_{4}

(square pyramidal).

💡 Tip · Uses

He

— weather balloons, cryogenics (liquid He cools NMR/MRI magnets), a breathing-gas diluent for divers.

Ne

— discharge tubes & advertising signs.

Ar

— inert atmosphere for welding and air-sensitive reactions.

🚫 Examiner Trap · Examiner traps

(1) Filled shell

\Rightarrow

very high IE,

positive

Δ_{e g} H

, inertness; He has the lowest boiling point of all (4.2 K). (2) Only

Xe

(and some Kr) form compounds, with F/O (Bartlett 1962). (3) Shapes: Xe

F_{2}

linear, Xe

F_{4}

square planar, Xe

F_{6}

distorted octahedral. (4) Hydrolysis: XeF

_{6} + 3 H_{2}

\to

O_{3}

(pyramidal)

+ 6

HF.

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Frequently Asked Questions

What are the most important The p-Block Elements formulas for NEET?

This The p-Block Elements formula sheet covers all the high-yield Chemistry formulas, definitions and facts you need for NEET, across General introduction; electronic configuration and trends (Groups 13-18), Anomalous behaviour of the first element of each group, Group 13 and 14 — properties and important compounds, Group 15, 16, 17 and 18 — properties and important compounds, Uses of p-block elements and their compounds — each shown with the key result and, where useful, a worked example.

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Blurt the The p-Block Elements key points from memory, then check against this sheet to find your gaps — and practise a few previous-year questions on the chapter to make sure you can apply them under time pressure.

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