Atomic Radius Order: Li > Be > B > C > N > O > F (Decreases left to right)

Ionization Potential (IP):

Trend: Increases across period, decreases down group.
Exception: $N > O$ (Half-filled $2p^3$ stability); $Be > B$ (Full $2s^2$ stability).
Highest IP: Helium (He)

Electron Affinity (EA): Chlorine (Cl) > Fluorine (F) > Bromine (Br) > Iodine (I)

Electronegativity (EN): F (4.0) > O (3.5) > N/Cl (3.0) > Br (2.8) > C/I/S (2.5) > H (2.1)

Diagonal Relationship: Li–Mg, Be–Al, B–Si

🎯 Direct hit: Hybridization Formula: $x = \frac{1}{2} [V + M - C + A]$
($V$ = Valence $e^-$, $M$ = Monovalent atom count, $C$ = Cation charge, $A$ = Anion charge).

Hybridization	$x$	Bond Angle	Shape	Examples
sp	2	180°	Linear	$BeCl_2, CO_2, C_2H_2$
sp²	3	120°	Trigonal Planar	$BF_3, BCl_3, C_2H_4$
sp³	4	109°28'	Tetrahedral	$CH_4, CCl_4, NH_4^+, Diamond$
sp³	4	107°	Pyramidal (1 LP)	$NH_3, PH_3, PCl_3$
sp³	4	104.5°	V-shape/Angular (2 LP)	$H_2O, H_2S$
sp³d	5	90°, 120°	Trigonal Bipyramidal	$PCl_5$
sp³d²	6	90°	Octahedral	$SF_6$
sp²d	4	90°	Square Planar	$[Cu(NH_3)_4]^{2+}$

Ionic Character Conditions:
- Fajans' Rule: Smaller cation + larger anion + high charge = More Covalent.
- EN difference > 1.7 = Ionic; < 1.7 = Covalent.
Bond Order (B.O.): $B.O. = \frac{Bonding e^- - Anti-bonding e^-}{2}$
- $N_2$ = 3; $O_2$ = 2; $CO$ = 3; $NO$ = 2.5; $He_2$ = 0.
Bond Power/Length:
- Power: $C\equiv C > C=C > C-C$.
- Length: $C-C$ (0.154 nm), $C=C$ (0.134 nm), $C\equiv C$ (0.120 nm), Benzene $C-C$ (0.139 nm).
Multiple Bonds:
- $NH_4Cl$: Ionic, Covalent, and Co-ordinate.
- $[Ag(NH_3)_2]Cl$: Ionic, Covalent, and Co-ordinate.
Hydrogen Bond:
- Strength: $H-F > H-O > H-N$.
- Boiling point increases with H-bond (e.g., $H_2O > H_2S$).
Lattice Stats:
- Cubic: $NaCl$, Diamond, $Cu$.
- Monoclinic: $Na_2SO_4 \cdot 10H_2O, FeSO_4 \cdot 7H_2O$.
- Hexagonal: Ice ($H_2O$).