Periodic Table Notes for NEET – Complete Chapter PDF

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LONG FORM OF PERIODIC TABLE

DEFINITION

Periodic Table = Tabular arrangement of elements.

Structure

7 Horizontal rows (Periods)
18 Vertical columns (Groups)
4 Blocks: s, p, d, f

Key Facts

First element → Alkali Metal
Last element → Inert Gas
Total periods = 7
Total groups = 18

Groups & Blocks Mapping

Group No.	Block	Max e⁻	No. of Groups
1 – 2	s-Block	2	2
3 – 12	d-Block	10	10
13 – 18	p-Block	6	6
3rd Group only	f-Block	14	1

⭐ MDJ (Most Done Jaata)

All f-block elements belong to 3rd group. 3rd group is the largest group of the Periodic Table.

Total 32 elements in 3rd group = 4 d-block + 14 Lanthanoids + 14 Actinoids

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PERIODS & GROUPS

Periods (n)

Period indicates 'n' for outermost shell
Each period starts from s-block
No. of periods in Periodic Table = 7

Period Subshells & Total Elements

Period (n)	Period Subshells	Total Elements	Inert Gas
1	1s	2	He (2)
2	2s → 2p	8	Ne (10)
3	3s → 3p	8	Ar (18)
4	4s → 3d → 4p	18	Kr (36)
5	5s → 4d → 5p	18	Xe (54)
6	6s → 4f → 5d → 6p	32	Rn (86)
7	7s → 5f → 6d → 7p	32	Og (118)

Energy Sequence Formula — (n+l) Rule

\[ n\,s \rightarrow (n-2)f \rightarrow (n-1)d \rightarrow n\,p \]

EXAMPLE — n = 6

\( 6s \rightarrow 4f \rightarrow 5d \rightarrow 6p \)

EXAMPLE — n = 7

\( 7s \rightarrow 5f \rightarrow 6d \rightarrow 7p \)

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BLOCKS — s, p, d, f

Name of block is decided by the orbital in which the last electron enters.

s-Block

Max e⁻ = 2
Groups: 1 & 2
MDJ: e⁻ must NOT be present in (n-1)d or (n-2)f subshell
Config: \([In]_{pre}\, ns^{1\text{ or }2}\)

p-Block

Max e⁻ = 6
Groups: 13 to 18
MDJ: 'np' subshell mein e⁻ hona zaroori hai
Config: \(ns^2\,np^{1\text{–}6}\)

d-Block

Max e⁻ = 10
Groups: 3 to 12
3d series (n=4): 4s 3d [₂₁Sc to Zn₃₀]
4d series (n=5): 5s 4d [₃₉Y to Cd₄₈]
5d series (n=6): 6s 4f 5d [La₅₇, Hf₇₂ to Hg₈₀]

f-Block

Max e⁻ = 14
Only 3rd Group
Total elements = 28
Lanthanoids: 6th Period / Z = 58–71
Actinoids: 7th Period / Z = 90–103

d-Block Series MDJ (Most Important)

Series	d⁴, d⁹ Nahi Honge	d⁵, d¹⁰ Repeat Honge
3d Series	d⁴ d⁹ Nahi honge	d⁵ d¹⁰ Repeat honge
4d Series	d³ d⁶ d⁹ Nahi honge	d⁵ d¹⁰ Repeat honge
5d Series	d⁸ Nahi hoge	d¹⁰ Repeat honge

f-Block MDJ Rules

Lanthanoids MDJ 1

f⁰ f² f⁸ Nahi honge
f⁷ f¹⁴ Repeat honge

Lanthanoids MDJ 2

Fill: [Xe] 6s² = 54+2 = 56e⁻
Gd, Ce, Lu = 5d¹
Remaining e⁻ in 4f

Actinoids MDJ 1

f¹ f⁵ f⁸ Nahi honge
f⁷ f¹⁴ Repeat honge

Actinoids MDJ 2

Fill: [Rn] 7s² = 86+2 = 88e⁻
Z=90 → d²
91,92,93,96,103 → d¹
Remaining in 5f

⚛️

ELECTRONIC CONFIGURATION

Block-wise General Configurations

Block	Outermost Configuration	Group No.
s	\(ns^{1-2}\)	ns electrons
p	\(ns^2\,np^{1-6}\)	12 + np electrons
d	\(ns^{0/1/2}\,(n-1)d^{1-10}\)	ns e⁻ + (n-1)d e⁻
f	\(ns^2(n-2)f^{1-14}(n-1)d^{0/1}\)	Always 3rd

3d Series Electronic Configurations

Element	Configuration	Element	Configuration
Sc (21)	\([Ar]\,3d^1\,4s^2\)	Fe (26)	\([Ar]\,3d^6\,4s^2\)
Ti (22)	\([Ar]\,3d^2\,4s^2\)	Co (27)	\([Ar]\,3d^7\,4s^2\)
V (23)	\([Ar]\,3d^3\,4s^2\)	Ni (28)	\([Ar]\,3d^8\,4s^2\)
*Cr (24)	\([Ar]\,3d^5\,4s^1\) ★	*Cu (29)	\([Ar]\,3d^{10}\,4s^1\) ★
Mn (25)	\([Ar]\,3d^5\,4s^2\)	Zn (30)	\([Ar]\,3d^{10}\,4s^2\)

4d Series Electronic Configurations

Element	Configuration	Element	Configuration
Y (39)	\([Kr]\,4d^1\,5s^2\)	*Ru (44)	\([Kr]\,4d^7\,5s^1\) ★
Zr (40)	\([Kr]\,4d^2\,5s^2\)	*Rh (45)	\([Kr]\,4d^8\,5s^1\) ★
*Nb (41)	\([Kr]\,4d^4\,5s^1\) ★	*Pd (46)	\([Kr]\,4d^{10}\,5s^0\) ★
*Mo (42)	\([Kr]\,4d^5\,5s^1\) ★	*Ag (47)	\([Kr]\,4d^{10}\,5s^1\) ★
Tc (43)	\([Kr]\,4d^5\,5s^2\)	Cd (48)	\([Kr]\,4d^{10}\,5s^2\)

5d Series Electronic Configurations

Element	Configuration	Element	Configuration
La (57)	\([Xe]\,4f^0\,5d^1\,6s^2\)	*Pt (78)	\([Xe]\,4f^{14}\,5d^9\,6s^1\) ★
Hf (72)	\([Xe]\,4f^{14}\,5d^2\,6s^2\)	*Au (79)	\([Xe]\,4f^{14}\,5d^{10}\,6s^1\) ★
W (74)	\([Xe]\,4f^{14}\,5d^4\,6s^2\)	Hg (80)	\([Xe]\,4f^{14}\,5d^{10}\,6s^2\)

EXCEPTIONS — Must Remember

Cr, Cu (3d), Nb, Mo, Ru, Rh, Pd, Ag (4d), Pt, Au (5d) — all exceptions due to extra stability of half-filled/fully-filled subshells
ns⁰ = Exception only for Pd; ns¹ = Exception for many

Solved Examples

Q: If Z = 34, Find n, Energy Sequence & Electronic Configuration

n = 4 (next inert gas Kr, n=4)

Energy sequence: \(4s \rightarrow 3d \rightarrow 4p\)

Config: \([Ar]\,3d^{10}\,4s^2\,4p^4\)

Q: If Z = 80, Find n, Energy Sequence & Electronic Configuration

n = 6 (next inert gas Rn, n=6)

Energy sequence: \(6s \rightarrow 4f \rightarrow 5d \rightarrow 6p\)

Config: \([Xe]\,4f^{14}\,5d^{10}\,6s^2\)

Q: Write Electronic Configuration for given Atomic Numbers

Z = 52 → \([Kr]\,5s^2\,4d^{10}\,5p^4\)
Z = 32 → \([Ar]\,4s^2\,3d^{10}\,4p^2\)
Z = 113 → \([Rn]\,7s^2\,5f^{14}\,6d^{10}\,7p^1\)

Lanthanoids Configurations

Element	Config	Element	Config
*Ce (58)	\([Xe]\,4f^1\,5d^1\,6s^2\)	Tb (65)	\([Xe]\,4f^9\,5d^0\,6s^2\)
Pr (59)	\([Xe]\,4f^3\,5d^0\,6s^2\)	Dy (66)	\([Xe]\,4f^{10}\,5d^0\,6s^2\)
Nd (60)	\([Xe]\,4f^4\,5d^0\,6s^2\)	Ho (67)	\([Xe]\,4f^{11}\,5d^0\,6s^2\)
Pm (61)	\([Xe]\,4f^5\,5d^0\,6s^2\)	Er (68)	\([Xe]\,4f^{12}\,5d^0\,6s^2\)
Sm (62)	\([Xe]\,4f^6\,5d^0\,6s^2\)	Tm (69)	\([Xe]\,4f^{13}\,5d^0\,6s^2\)
Eu (63)	\([Xe]\,4f^7\,5d^0\,6s^2\)	Yb (70)	\([Xe]\,4f^{14}\,5d^0\,6s^2\)
*Gd (64)	\([Xe]\,4f^7\,5d^1\,6s^2\)	*Lu (71)	\([Xe]\,4f^{14}\,5d^1\,6s^2\)

Actinoids Configurations

Element	Config	Element	Config
Th (90)	\([Rn]\,5f^0\,6d^2\,7s^2\)	Bk (97)	\([Rn]\,5f^9\,6d^0\,7s^2\)
Pa (91)	\([Rn]\,5f^2\,6d^1\,7s^2\)	Cf (98)	\([Rn]\,5f^{10}\,6d^0\,7s^2\)
U (92)	\([Rn]\,5f^3\,6d^1\,7s^2\)	Es (99)	\([Rn]\,5f^{11}\,6d^0\,7s^2\)
Np (93)	\([Rn]\,5f^4\,6d^1\,7s^2\)	Fm (100)	\([Rn]\,5f^{12}\,6d^0\,7s^2\)
Pu (94)	\([Rn]\,5f^6\,6d^0\,7s^2\)	Md (101)	\([Rn]\,5f^{13}\,6d^0\,7s^2\)
Am (95)	\([Rn]\,5f^7\,6d^0\,7s^2\)	No (102)	\([Rn]\,5f^{14}\,6d^0\,7s^2\)
Cm (96)	\([Rn]\,5f^7\,6d^1\,7s^2\)	Lr (103)	\([Rn]\,5f^{14}\,6d^1\,7s^2\)

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IUPAC NOMENCLATURE (Z > 100)

Rules

Use suffix "ium" at the end. Build name from individual digits of Z.

Digit	Root	Digit	Root
0	nil	5	pent
1	un	6	hex
2	bi	7	sept
3	tri	8	oct
4	quad	9	enn

EXAMPLES

Z = 105 → 1-0-5 → Un-nil-pent+ium → Unnilpentium [Unp]
Z = 117 → 1-1-7 → Un-un-sept+ium → Ununseptium [Uus]
Z = 113 → 1-1-3 → Un-un-tri+ium → Ununtrium [Uut]

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GROUP, BLOCK & PERIOD IDENTIFICATION

Case 1: When Atomic Number (Z) is Given

Finding Period (n)

'n' of Z given = n of next inert gas

EXAMPLE

Z = 51 → Next inert gas = 54 (Xe, n=5) → n = 5 for Z = 51

Finding Group Number

\[ \text{Group No.} = Z_{\text{given}} + 18 - Z_{\text{next inert gas}} \]

⚠️ Do NOT apply for f-block & Z up to 12.
If result is negative → use 32 instead of 18.

EXAMPLE — Z = 25 (n = 4)

Gp No. = 25 + 18 − 36 = 7th group (d-Block)

EXAMPLE — Z = 57 (n = 6)

Gp No. = 57 + 18 − 86 = −11 (Negative!) → Use 32

Gp No. = 57 + 32 − 86 = 3rd group (d-Block) ✓

MDJ RULES

If \(58 \leq Z \leq 71\) → f-block, n=6, Always 3rd Group
If \(90 \leq Z \leq 103\) → f-block, n=7, Always 3rd Group
If \(104 \leq Z \leq 118\) → Gp No. = last two digits of Z (e.g. Z=112 → 12th group)

How to Find Block from Group No.

Group No.	Block
1 – 2	s-Block
3 – 12	p-Block
13 – 18	d-Block

Case 2: When Electronic Config is Given

Finding Period (n)

n = maximum value of n in given configuration

Example: \(1s^2\,2s^2\,2p^6\,3s^2\,3p^1\) → n = 3

Exception — Pd (Z=46)

\([Kr]\,4d^{10}\,5s^0\) → n→5, but outermost shell is 4th. Only Pd has 18e⁻ in its outermost shell.

Finding Group from Config — Summary

Block	Outermost Config	Group No.
S	\(ns^{1-2}\)	ns electrons
P	\(ns^2\,np^{1-6}\)	12 + np e⁻
d	\(ns^{0/1/2}\,(n-1)d^{1-10}\)	ns e⁻ + (n-1)d e⁻
f	\(ns^2(n-2)f^{1-14}(n-1)d^{0/1}\)	Always 3rd

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SCREENING EFFECT & EFFECTIVE NUCLEAR CHARGE

Screening / Shielding Effect

Tendency of inner electrons to shield outer electrons from nuclear charge.

Repulsive force exerted by inner e⁻ towards outer (test) e⁻.

Order of Shielding for Different Subshells of Same Shell

\[ s > p > d > f \quad \text{(d, f = Poor Shielding)} \]

Shielding is represented by sigma (σ)

Effective Nuclear Charge (Z_eff)

Remaining force of attraction on test e⁻ after shielding. (Net Attraction)

\[ Z_{eff} = Z_i - \sigma \]

Z_i = total attraction | σ = total repulsion

If σ ↓, Z_eff ↑ due to:

(i) Transitional Contraction: Due to poor σ of 3d e⁻ → Z_eff ↑
(ii) Lanthanoid Contraction: Due to poor σ of 4f e⁻ → Z_eff ↑
(iii) Actinoid Contraction: Due to poor σ of 5f e⁻ → Z_eff ↑

Power of Contraction

Transitional Contraction < Lanthanoid Contraction < Actinoid Contraction

General Trend of Z_eff

Moving Left → Right (n constant): Z_eff increases
Moving Down the group (n increases): Z_eff Constant

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ATOMIC RADIUS

Radius of individual atom cannot be measured because:

(i) Size of atom is very small (~1-2 Å)
(ii) There is no sharp boundary as it is surrounded by e⁻ cloud

Radius is always measured in bonded state.

\[ r = \frac{d}{2} \quad \text{where d = Internuclear distance} \]

Types of Radius

Type	Formula	Use
(i) Covalent Radius	\(r_c = d_{cov}/2\)	Covalent compounds
(ii) Metallic Radius	\(r_M = d_M/2\)	Metal lattices
(iii) Van der Waals Radius	\(r_V = d_V/2\)	Noble gases, non-bonded
(iv) Ionic Radius	Size of Ions	Ionic compounds

Order

\[ r_c < r_M < r_V \]

Ionic Radius

Cation (M⁺)

Always smaller than parent species
Z_eff ↑ after removal of e⁻
\(M > M^+ > M^{2+} > M^{3+}\)

Anion (X⁻)

Larger than parent species
Z_eff ↓ due to increase in e⁻
\(X < X^- < X^{2-} < X^{3-}\)

Isoelectronic Species

Having same no. of e⁻

Order: \(Mg^{2+} < Na^+ < F^- < O^{2-} < N^{3-}\) (Size increases)

MDJ for Isoelectronic as well as ions of same element:

Ionic size ∝ −ve charge / +ve charge
Ionic size ∝ 1/Z_eff

General Trend of Atomic Size

Left → Right (Z_eff ↑) → Size Decreases

Down the group (n ↑) ↓ Size Increases

Block-wise Size — S-Block

No Exception in S-Block

Be < Li < Mg < Na < Ca < Sr < Ba < K < Rb < Cs

Ionic Radius order:

\(Be^{2+} < Mg^{2+} \leq Li^+ < Na^+ < Ca^{2+} < Sr^{2+} < Ba^{2+} < K^+ < Rb^+ < Cs^+\)

Block-wise Size — P-Block

Group 13: B < Ga < Al < In < Tl (Inversion due to poor shielding of 3d e⁻ → Transition Contraction)
Group 14: C < Si < Ge < Sn ≈ Pb (Lanthanoid Contraction)
Group 15: N < P < As < Sb < Bi (No exception gp 14 to 18)
Group 16: O < S < Se < Te < Po
Group 17: F < Cl < Br < I
Group 18: He < Ne < Ar < Kr < Xe

Block-wise Size — D-Block (3d series, Left to Right)

Sc > Ti > V > Cr < Mn > Fe ≈ Co = Ni < Cu < Zn

Sc > Zn (important comparison)
Mn = Zn (both anomalous)
Very less variation in size (L→R as well as T→B) due to this property d-block metals form Alloy

Block-wise Size — F-Block (Lanthanoids)

Ce > Pr > Nd > Pm > Sm < Eu > Gd > Tb > Dy > Ho > Er > Tm > Yb > Lu

LANTHANOID IONIC RADIUS ORDER (M³⁺) — No Exception

\(Ce^{+3} > Pr^{+3} > Nd^{+3} > Pm^{+3} > Sm^{+3} > Eu^{+3} > Gd^{+3} > Tb^{+3} > Dy^{+3} > Ho^{+3} > Er^{+3} > Tm^{+3} > Yb^{+3} > Lu^{+3}\)

Q: Last Element of p-block in 6th period is represented by outermost electronic configuration:

✅ Ans: (c) 4f¹⁴ 5d¹⁰ 6s² 6p⁶

MDJ — Generally

Metals are larger in size than non-metals.

F < Cl < Br < I < Li (Non-metal < Metal)

Order with reason for F⁻, Cl⁻, Br⁻, I⁻, H⁻

F⁻ < Cl⁻ < Br⁻ < H⁻ < I⁻

H + e⁻ → H⁻ (1e⁻ in 1p → 2e⁻ in 1p; Z_eff ↑ by 50% → size ↑)

Li > Be > B > C > N > O > F << Ne

Reason: For Inert gas, Van der Waals radius is considered

⚡

IONISATION ENERGY

DEFINITION

Minimum required energy to remove most loosely bounded e⁻ from gaseous isolated atom.

Note: Always Endothermic for Neutral & Cations.

Q: In which of the following the energy change corresponds to first ionisation potential?

✅ Ans: (a) \(X_2(g) \rightarrow X^+(g) + e^-\)

Value of Successive Ionisation Energy

\[ M(g) \xrightarrow{IE_1} M^+(g) \xrightarrow{IE_2} M^{2+}(g) \xrightarrow{IE_3} M^{3+}(g) \] \[ IE_3 > IE_2 > IE_1 \]

Factors Affecting Ionisation Energy

① Size

\[ IE \propto \frac{1}{\text{Size}} \]

② Z_eff

\[ IE \propto \frac{Z_{eff}}{\sigma} \]

③ Stable Configuration

Fully filled (Inert gas config) — Extra stability → Higher IE
Half filled — Extra stability → Higher IE
Max ionisation energy in a period → Inert gas

④ Penetration Power

\[ s > p > d > f \]

e.g. Be > B (2s² vs 2p¹); Mg > Al (3s² vs 3p¹)

I.E. of 2nd Period

Li < Be > B < C < N > O < F < Ne
(2s¹) (2s²) (2p¹) (2p²) (2p³) (2p⁴) (2p⁵) (2p⁶)

Final Order (2nd Period)

Li < B < Be < C < O < N < F < Ne

I.E. of 3rd Period

Na < Mg > Al < Si < P > S < Cl < Ar
(3s¹) (3s²) (3p¹) (3p²) (3p³) (3p⁴) (3p⁵) (3p⁶)

Final Order (3rd Period)

Na < Al < Mg < Si < S < P < Cl < Ar

MDJ

If value of n is same, Ionisation Energy order:

\(ns^1 < np^1 < ns^2 < np^2 < np^4 < np^3 < np^5 < np^6\)

IE Order of 2nd I.E.

How to write 2nd I.E.

IE₂ = removal of 2nd e⁻ (means 1st has already been removed → reduce 1e⁻ from configuration)

Order of 2nd I.E. of C, N, O & F

After removing 1 e⁻: C(2p¹), N(2p²), O(2p³), F(2p⁴)

Order: 2p¹ < 2p² < 2p⁴ < 2p³

C < N < F < O

Order of 2nd I.E. of Na, Mg, Al & Si

After removing 1 e⁻: Na(2p⁶), Mg(3s¹), Al(3s²), Si(3p¹)

Order: 3s² < 3p¹ < 3s² < 2p⁶

Mg < Si < Al < Na

Block-wise Ionisation Energy

S-Block — No Exception

Moving Left → Right: I.E. ↑
Moving Down the group: I.E. ↓
IE₁: AM < AEM (ns¹ vs ns²)
But IE₂: AM > AEM (after removing 1e⁻: ns⁰/np⁶ vs ns¹)

P-Block IE (Top to Bottom)

Group 15th, 16th, 17th, 18th: IE increases top to bottom (No exception)
Group 13th: B > Tl > Ga > Al > In (Final order)
Group 14th: C > Si > Ge > Pb > Sn (Final order)

D-Block IE (Top to Bottom)

Group 3: 3d < 4d < 5d (No Lanthanoid Contraction)
Group 4–6, 10: 3d > 4d < 5d (Lanthanoid Contraction)
Group 7–9, 11, 12: 4d < 3d < 5d
Note: IE of 5d series element in each group (except 3rd) is maximum due to Lanthanoid Contraction

3d series (Left to Right): Sc < V < Co < Ti < Mn < Ni < Cu < Co < Fe < Zn

Important d-Block Comparisons

Elements	IE₁	IE₂	Reason
Cr vs Mn	Cr < Mn (4s¹ vs 4s²)	Cr > Mn (3d⁵ stable)	Half-filled 3d
Cu vs Zn	Cu < Zn (4s¹ vs 4s²)	Cu > Zn (3d¹⁰ stable)	Fully filled 3d

Applications of I.E.

① Metallic Character / Electropositive Character

When I.E. ↓ → e⁻ removal becomes easy → Metallic Character ↑ → Reactivity ↑

② No. of Valence e⁻ & Possible Oxidation States

Large jump between two successive IE values indicates the number of valence electrons.

EXAMPLE

Element X: IE₁(6eV), IE₂(8.5eV), IE₃(122eV), IE₄(119eV)

No. of valence e⁻: 2
Possible O.S.: +2
Formula of O²⁻: X²⁺ + O²⁻ → XO
Formula of N³⁻: X²⁺ + N³⁻ → X₃N₂
Element X is most likely to be: Mg

③ Stability of Lower O.S. & Higher O.S.

Rule 1 (Only for s-block): If ΔI.E. ≤ 11eV → Higher O.S. will be more stable (M²⁺ > M⁺)

Rule 2 (For Alkali Metal): If ΔI.E. ≥ 16eV → Lower O.S. will be more stable (M⁺ > M²⁺)

MDJ — IE of Ion

I.E. of ion ∝ +ve charge / −ve charge

Q: Write correct order of I.E. for O, O⁺, O²⁺

O < O⁺ < O²⁺

Q: Write correct order of I.E. for I⁺, I, I⁻

I⁺ > I > I⁻

Q: N³⁻, O²⁻, F⁻, Na⁺, Mg²⁺ — Write correct I.E. order

N³⁻ < O²⁻ < F⁻ < Na⁺ < Mg²⁺

Q: Which of the following has 2nd IP < 1st IP?

✅ Ans: (d) None — 2nd IE is always greater than 1st IE

Q: If the graph is b/w atomic no. & Ionisation potential, which group of elements occupy lowest position on curve?

✅ Ans: (d) Alkali Metals

F-Block IE

Irregular Variations
IE₁ & IE₂ of Lanthanoids are similar to Ca
IE₃ of Lanthanoids are similar to Al

🔋

ELECTRON GAIN ENTHALPY

Definitions

Electron Affinity (EA): Tendency to gain e⁻

Electron Gain Enthalpy (ΔegH): When an e⁻ is added to neutral gaseous atom to convert it into a −ve ion, the enthalpy change accompanying the process is defined as Electron Gain Enthalpy (ΔegH).

Key Rules

Electron Affinity is measured in term of electron gain enthalpy
For Neutral atom: ΔHeg is exothermic except N, Alkaline Earth Metals & Inert gases [AEM: Mg, Be]
ΔHeg of cation is always Exothermic
ΔHeg of anion is always Endothermic (formation of poly-negative atoms)

Exothermic & Endothermic Processes

Process	Type	Process	Type
\(N + e^- \rightarrow N^-\)	Endothermic	\(O + e^- \rightarrow O^-\)	Exothermic
\(O + 2e^- \rightarrow O^{2-}\)	Endothermic	\(S + 2e^- \rightarrow S^{2-}\)	Endothermic
\(Be + e^- \rightarrow Be^-\)	Endothermic	\(F + e^- \rightarrow F^-\)	Exothermic
\(Ne + e^- \rightarrow Ne^-\)	Endothermic	\(O^+ + e^- \rightarrow O\)	Exothermic
\(Na^+ + e^- \rightarrow Na\)	Exothermic	\(O_2^+ + e^- \rightarrow O_2^+\)	Exothermic (MDJ)
\(O^+ + e^- \rightarrow O\)	Exothermic	\(O^- + e^- \rightarrow O^{2-}\)	Endothermic

Electron Affinity	Electron Gain Enthalpy (ΔHeg)
e⁻ Bulane ki neeyat (tendency)	Change in Enthalpy during addition of an e⁻
When EA is +ve	ΔHeg will be −ve (Exothermic)
When EA is −ve or Zero	ΔHeg will be +ve (Endothermic) or towards +ve

Relation b/w EA & IE

\[ X + e^- \rightarrow X^- \quad [EA][Exo][\Delta H_{eg}: -100] \] \[ X^- \rightarrow X + e^- \quad [IE][Endo][\Delta H_{ie}: +100] \] \[ |EA \text{ of } X| = |IE \text{ of } X^-| \]

MDJ

IE (Absorbed Energy) of any element is always greater than EA (released energy)

Factors Affecting Electron Affinity

① Size

\[EA \propto \frac{1}{\text{Size}}\]

② Z_eff

\[EA \propto Z_{eff} = \frac{1}{\text{Screening}}\]

③ Stable Configuration

Zero EA of Inert gas
np² > np³; e.g. C > N, Si > P

④ Penetration Power

np² > np¹; e.g. Li > B, Na > Al

EA Order — 2nd & 3rd Period

2nd Period Order

Ne < Be < N < B < Li < C < O < F

3rd Period Order

Ar < Mg < Al < Na < P < Si < S < Cl

Maximum EA in Periodic Table

Chlorine (Cl) — NOT Fluorine!

F has smaller 2p orbital → high electron density → more repulsion for incoming e⁻. 3rd period elements have more EA than 2nd period elements.

Q: Why EA of 3rd period elements is more than EA of 2nd period elements?

Fluorine [He]2s²2p⁵ — 2nd period, Small size of 2p, High surface e⁻ density, More repulsion for new e⁻, Less attraction for new e⁻ → Less EA

Chlorine [Ne]3s²3p⁵ — 3rd period, Large size of 3p, Low surface e⁻ density, Less repulsion for new e⁻, More attraction for new e⁻ → More EA

Important Orders

Oxygen family EA: S > Se > Te > Po > O

Halogen family EA: Cl > F > Br > I > At

Q: Inert gases have +ve electron gain enthalpy. The correct order is:

✅ Ans: (c) He < Rn < Xe < Ar ≈ Kr < Ne

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ELECTRONEGATIVITY

DEFINITION

The tendency of an atom to attract the shared pair of electrons towards itself.

It does NOT depend on electronic configuration.

ΔEN ↑ → % Ionic Character ↑
ΔEN ↑ → Bond Polarity ↑

Factors Affecting Electronegativity

① Size

\[EN \propto \frac{1}{\text{Size}}\]

② Z_eff

\[EN \propto Z_{eff}\]

③ Oxidation State

\[EN \propto O.S.\]

④ % s Character

\[EN \propto \%s\text{ character}\]

% s Character → Hybridization & EN

Hybridization	sp	sp²	sp³
% s character	50%	33%	25%
% p character	50%	67%	75%

\[ EN: sp > sp^2 > sp^3 \]

e.g. Carbon EN: Csp (3.25) > Csp² (2.75) > Csp³ (2.50)

Note: Same element can show diff. EN values in diff. Oxidation state & diff. hybrid state

Different Scales of EN

① Pauling Scale

Based on bond energy calculation.

Element	EN	Element	EN
H	2.1	F (Highest)	4.0
C	2.5	Cl	3.0
N	3.0	S	2.5
O	3.5	P	2.1

② Mullikan Scale

Based on IP & EA.

\[ EN_{MS} = \frac{IP + EA}{2} \qquad EN_{Pauling} = \frac{EN_{Mulliken}}{2.8} \]

Applications of Electronegativity

① Non-metallic Character

EN ↑ → NMC ↑

Generally: Left → Right: EN ↑, NMC ↑ | Top → Bottom: EN ↓, NMC ↓

② Acidic/Basic/Amphoteric Nature of Oxide/Hydrides

A—O—H bond: If A—O bond is more polar → breaks → gives OH⁻ → Base

If O—H bond is more polar → breaks → gives H⁺ → Acid

MDJ: Zyada polar bond tutega

Generally Metal Oxides are Basic in nature.

Generally Non-metal Oxides are Acidic in nature.

CO, NO, N₂O, H₂O are Neutral

Amphoteric Oxides/Hydroxides

Can act as acid as well as base:

ZnO, BeO, Al₂O₃, Sb₂O₃, As₂O₃, PbO, SnO, Ga₂O₃, Cr₂O₃

For d-Block

Variable O.S. shown by element:

O.S. +1, +2, +3 → Basic
O.S. +4 → Amphoteric
O.S. +5, +6, +7, +8 → Acidic

③ % Ionic Character

\[ \% IC = 16\Delta EN + 3.5(\Delta EN)^2 \]

EXAMPLE

If EN values of element X & Y are 2.8 and 4.8 respectively, find % IC of compound XY:

% IC = 16 × 2 + 3.5(2)² = 32 + 14 = 46%

④ Internuclear distance in heteroatomic molecule

\[ d_{A-B} = r_A + r_B - 0.09(\Delta EN) \]

where \(r_A = d_{A-A}/2\) and \(r_B = d_{B-B}/2\)

Q: EN of following elements increases in order:

✅ Ans: (b) P < S < N < O

Q: Compare acidic/basic nature

NaOH > Mg(OH)₂ > Al(OH)₃ > Si(OH)₄ [Basic order]
Li₂O < Na₂O < K₂O [Basic order]
Li₂O < BeO < B₂O₃ [Acidic order]
P₄O₁₀ < SO₃ < Cl₂O₇ [Acidic order]
MnO > Mn₂O₃ > Mn₂O₇ [Basic order]
HNO₂ < HNO₃ [Acidic order]
HClO₂ < HClO₃ < HClO₄ [Acidic order]

📜

GENESIS OF PERIODIC CLASSIFICATION

① Dobereiner Triads

Li Na K is Dobereiner Triads because atomic wt. of Na is equal to avg. atomic wt. of Li & K.

MDJ: Same Group | ΔZ same

Examples: ₃Li, ₁₁Na, ₁₉K | ₄Be, ₁₂Mg, ₂₀Ca | ₁₇Cl, ₃₅Br, ₅₃I

② De-Chanchortious

3D model & DNA Helix structure.

③ Newland Octave Rule

Sa Re Ga Ma Pa Dha Ni Sa... (every 8th element resembles)

MDJ: Same group | ΔZ = 8

Examples: Be, Mg, Ca (ΔZ=8)

Disadvantage: Newland law of octane seemed to be true only for elements upto Calcium and after invention of Inert gas this rule got totally failed.

④ Lothar Meyer Curve

Plotted graph b/w atomic mass & atomic volume.

Peak position: Alkali metal
Descending: Alkaline Earth metal
Ascending: Halogens
Bottom part: d-block elements

⑤ Mendeleev's Periodic Table

"The properties of elements are a periodic function of the atomic weights"

Advantages:

Discovery of new elements (Eka-Aluminium → Ga, Eka-Boron → Sc, Eka-Silicon → Ge, Eka-Manganese → Tc)
Correction in atomic wt. of some elements: Au (Gold), In (In), Pt (Platinum), Be (Beryllium), U (Uranium)

Disadvantages:

Some elements do not follow trend of increasing atomic wt.
(i) Ar – K (Amir – Khan) (ii) Te – I (Teri – Iccha)
(iii) Th – Pa (Thanda – Pepsi) (iv) Co – Ni (Kyo – Nahi)

Some Important Terms

Term	Definition
Representative Elements / Main group elements	s-Block + p-Block
Halogens	Group 17th
Chalcogens	Group 16th
Pnictogens	Group 15th
Nobel Gases	Group 18th
Lanthanoids	Z = 58 – 71
Actinoids	Z = 90 – 103
Transition Elements (IUPAC)	d-block elements having partially filled (n-1)d subshell either in neutral or in any common ionic state
Transuranium Elements	All f-block elements having Z > 92
Ultimate Shell	nth shell
Penultimate Shell	(n-1)th shell

Q: Is Ag a Transition Element?

Ag = [Kr] 4d¹⁰ 5s¹ | Ag⁺ = [Kr] 4d¹⁰ 5s⁰ | Ag²⁺ = [Kr] 4d⁹ 5s⁰ ✓

Yes, Ag is a Transition element because Ag in its O.S. of +2 has partially filled (n-1)d subshell.

PERIODIC TABLENOTES

LONG FORM OF PERIODIC TABLE

Groups & Blocks Mapping

PERIODS & GROUPS

Period Subshells & Total Elements

Energy Sequence Formula — (n+l) Rule

BLOCKS — s, p, d, f

d-Block Series MDJ (Most Important)

f-Block MDJ Rules

ELECTRONIC CONFIGURATION

Block-wise General Configurations

3d Series Electronic Configurations

4d Series Electronic Configurations

5d Series Electronic Configurations

Solved Examples

Lanthanoids Configurations

Actinoids Configurations

IUPAC NOMENCLATURE (Z > 100)

GROUP, BLOCK & PERIOD IDENTIFICATION

Case 1: When Atomic Number (Z) is Given

How to Find Block from Group No.

Case 2: When Electronic Config is Given

Finding Group from Config — Summary

SCREENING EFFECT & EFFECTIVE NUCLEAR CHARGE

Effective Nuclear Charge (Z_eff)

ATOMIC RADIUS

Types of Radius

Ionic Radius

Isoelectronic Species

General Trend of Atomic Size

Block-wise Size — S-Block

Block-wise Size — P-Block

Block-wise Size — D-Block (3d series, Left to Right)

Block-wise Size — F-Block (Lanthanoids)

IONISATION ENERGY

Value of Successive Ionisation Energy

Factors Affecting Ionisation Energy

I.E. of 2nd Period

I.E. of 3rd Period

IE Order of 2nd I.E.

Block-wise Ionisation Energy

Important d-Block Comparisons

Applications of I.E.

F-Block IE

ELECTRON GAIN ENTHALPY

Exothermic & Endothermic Processes

Relation b/w EA & IE

Factors Affecting Electron Affinity

EA Order — 2nd & 3rd Period

ELECTRONEGATIVITY

Factors Affecting Electronegativity

Different Scales of EN

Applications of Electronegativity

GENESIS OF PERIODIC CLASSIFICATION

① Dobereiner Triads

② De-Chanchortious

③ Newland Octave Rule

④ Lothar Meyer Curve

⑤ Mendeleev's Periodic Table

Some Important Terms

PERIODIC TABLE
NOTES