Group 18 Elements

Electronic Configuration: — $ns^2np^6$ (except He: $1s^2$).
Inertness: — Due to stable, filled valence shell.
Ionization Enthalpy (IE): — Very high, decreases down group.
Electron Gain Enthalpy (EGE): — Highly positive (unfavorable).
Boiling Points: — Very low, increases down group (due to increasing London forces).
Physical State: — Monoatomic gases, colorless, odorless, tasteless.
Xenon Compounds: — XeF$_2$ (linear, $sp^3d$), XeF$_4$ (square planar, $sp^3d^2$), XeF$_6$ (distorted octahedral, $sp^3d^3$), XeO$_3$ (pyramidal, $sp^3$), XeOF$_4$ (square pyramidal, $sp^3d^2$).
Uses: — He (cryogenics, diving), Ne (neon signs), Ar (inert atmosphere, bulbs), Kr (flash lamps), Xe (high-intensity lamps), Rn (radiotherapy).

To remember the order of noble gases and their increasing boiling points: Heavy New Army Kry Xenophobes Really Need. (He, Ne, Ar, Kr, Xe, Rn). For Xenon compounds and their shapes, visualize the central Xe atom and count electron pairs for VSEPR: 'Two Fs, Linear; Four Fs, Square; Six Fs, Distorted Octa; Three Os, Pyramidal; Four Fs and One O, Square Pyramidal.'