Properties of Elements and Compounds – Groups IA, IIA, VIA, VIIA, VIIIA

Vocabulary flashcards summarizing the key properties and behaviors of element groups IA, IIA, VIA, VIIA, VIIIA, hydrogen’s unique position, and related chemical trends.

Alkali Metals (Group IA)

Li, Na, K, Rb, Cs, Fr; 1 valence electron, oxidation state +1, very reactive, low density, soft, react violently with water to give MOH and H₂.

Alkaline Earth Metals (Group IIA)

Be, Mg, Ca, Sr, Ba, Ra; 2 valence electrons, oxidation state +2, moderate reactivity, react with water (Mg slowly), form mostly ionic compounds.

Chalcogens (Group VIA)

O, S, Se, Te, Po; 6 valence electrons, oxidation states –2 → +6, often form network covalent lattices with high melting and boiling points.

Halogens (Group VIIA)

F, Cl, Br, I, At; 7 valence electrons, oxidation states –1 → +7, diatomic molecules, strong oxidizers, form acids and many salts.

Noble Gases (Group VIIIA)

He, Ne, Ar, Kr, Xe, Rn; full valence shell (He = 2, others = 8), chemically inert, highest ionization energies in the periodic table.

Alkali metal–water reaction

2 M + 2 H₂O → 2 MOH + H₂; vigorous, exothermic, produces a strong base and hydrogen gas.

Alkaline earth metal–water reaction

M + 2 H₂O → M(OH)₂ + H₂ (for Mg, reaction requires hot water); less vigorous than alkali metals.

Storage of Alkali Metals

Kept under oil or kerosene to prevent reaction with moisture and oxygen in air.

Solubility of Alkali Metal Compounds

All alkali metal salts are water-soluble except potassium perchlorate (KClO₄).

Insoluble Group IIA Salts

Carbonates, sulfates, and phosphates of Ca, Sr, Ba are insoluble; MgSO₄ is a notable soluble exception.

Network Covalent Structure

Extended 3-D lattice held by covalent bonds (e.g., S₈ rings, Se chains); yields very high melting/boiling points.

Diatomic Molecule

Molecule composed of two atoms; all halogens exist naturally as X₂ (F₂, Cl₂, Br₂, I₂, At₂).

Colors of Halogens

F₂ pale yellow, Cl₂ greenish-yellow, Br₂ brown/red-brown, I₂ violet-purple.

Oxidizing Strength Trend (Halogens)

Decreases down the group: F₂ > Cl₂ > Br₂ > I₂; stronger halogen can oxidize the ion of a weaker one.

Ionization Energy of Noble Gases

Highest of all elements due to filled valence shells; He has the greatest IE value.

Van der Waals Radius

Effective size of non-bonded atoms; noble gas radii increase down a period because only weak VDW forces are present.

Dual Position of Hydrogen

Shares traits with Group IA (1 valence electron, +1 state) and Group VIIA (forms H⁻, diatomic gas, high EN & IE).

Oxidation States of Hydrogen

Commonly +1 (water, acids) and –1 (metal hydrides); higher positive states (+3, +5, +7) occur in polyatomic ions.

Valence Electron Count by Group

IA = 1, IIA = 2, VIA = 6, VIIA = 7, VIIIA = 8 (He = 2); determines typical bonding patterns.

Density of Alkali Metals

Very low; Li, Na, and K can float on water due to densities below 1 g cm⁻³.

Melting/Boiling Points of Alkali Metals

Relatively low compared with most metals because of weak metallic bonding.

Reactivity Trend in Group IA

Increases down the group: Li < Na < K < Rb < Cs < Fr.

Oxidation State Range of Chalcogens

From –2 (sulfides, oxides) up to +6 (sulfates, chromyl-like species).

Noble Gas Compounds

Formed mainly by Kr and Xe with highly electronegative F or O, e.g., XeF₂, XeO₃; require extreme conditions.

Insoluble Halide Salts

Halides of Ag⁺, Hg₂²⁺, and Pb²⁺ (e.g., AgCl, PbI₂) are largely insoluble in water.