The p-Block Elements (Groups 13-18) — Vocabulary Flashcards

Vocabulary flashcards covering key terms and definitions from the p-block element chapters (Groups 13–18), including electronic configurations, trends, allotropes, oxides, acids, interhalogens, and noble gas chemistry.

p-block elements

Elements in Groups 13 to 18 of the periodic table with valence shell configuration ns2 np1-6 (He = 1s2).

valence shell electronic configuration of p-block elements

ns2 np1-6 (except He which is 1s2).

absence/presence of d orbitals across Group 15

Second-period elements lack d orbitals; heavier elements have d or f orbitals, influencing bonding and covalency.

Group 15 electronic configuration

ns2 np3.

Nitrogen’s anomalous bonding in Group 15

Small size, high electronegativity, no d orbitals; forms N≡N triple bond and can form pπ-pπ bonds with O or C.

Dinitrogen (N2) in the atmosphere

Makes up about 78% by volume of the atmosphere.

Nitrate minerals in the earth’s crust

Sodium nitrate (NaNO3, Chile saltpetre) and potassium nitrate (KNO3, Indian saltpetre).

Haber process

Industrial synthesis of NH3: N2 + 3H2 → 2NH3 under high pressure (~200 atm) and high temperature (~700 K) with an iron catalyst.

Ammonia as a Lewis base

NH3 has a lone pair on N and donates it to metal centers (e.g., forming [Cu(NH3)4]2+).

Ostwald (nitric acid) process

Industrial production of HNO3 by catalytic oxidation of NH3 to NO/NO2 and subsequent absorption to form HNO3.

Phosphorus allotropes

White, red, and black phosphorus; white P is highly reactive and glows in air; red/black are less reactive.

Phosphine (PH3) properties

Colorless, highly poisonous gas; slightly soluble in water; acts as a Lewis base and forms PH4+ with acids; PH3 is less basic than NH3.

Phosphorus halides (PX3 and PX5)

PX3 (X = F, Cl, Br, I) and PX5; PCl3 prepared from white phosphorus with Cl2; PCl5 from P with Cl2; PX5 hydrolyses to POCl3 and H3PO4.

Oxoadic acids of phosphorus

Oxoacids containing P=O and P–OH bonds (e.g., H3PO4; H3PO3); P–H bonds occur in lower oxidation states and influence reducing properties.

Basicity of phosphorus oxoacids

Acids with P–OH groups are dibasic or tribasic (H3PO3 is dibasic; H3PO4 is tribasic) because only P–OH hydrogens ionize.

Group 16 elements (the chalcogens)

O, S, Se, Te, Po; ns2 np4; show oxidation states -2, +4, +6; allotropy; electronegativity decreases down the group.

Oxygen’s anomalous behaviour

Small size and high electronegativity limit covalence; strong H-bonds in H2O; oxygen lacks d orbitals for expanded covalence.

Hydrides of Group 16 (H2E)

H2O, H2S, H2Se, H2Te, HPo; acidity increases down the group; hydrides are generally reducing (H2O is not a strong reducing agent).

Group 17 (halogens) electronic configuration

ns2 np5; six outer electrons; typical oxidation state is -1; fluorine often shows no higher oxidation states due to no d orbitals.

Interhalogen compounds

Compounds XX′, XX3′, XX5′, XX7′ formed by reaction of halogens; examples include ClF3, IF7; shapes and hydrolysis products explain their reactivity.

Noble gases (Group 18)

He, Ne, Ar, Kr, Xe, Rn; closed-shell, largely inert; Xe forms XeF2, XeF4, XeF6 and XeO3; uses include inert atmospheres and cryogenics.

Ozone (O3)

Allotrope of oxygen; prepared by silent discharge; pale blue gas; powerful oxidising agent; decomposes to O2.

Dioxygen (O2) properties

Paramagnetic gas; solubility in water ~3.08 cm3 per 100 cm3 at 293 K; boiling point 90 K; bond energy ~493 kJ/mol.

Sulphur dioxide (SO2)

Oxidation product of S; soluble in water to give HSO3−; reduces Fe3+ to Fe2+; used in sulphuric acid production and as a refining gas.

Sulphuric acid (H2SO4) and the Contact process

SO2 is oxidised to SO3 over V2O5; SO3 absorbed in H2SO4 to give oleum; dilution yields H2SO4 (96-98%); highly exothermic and dehydrating.

Oxides classification

Acidic oxides, basic oxides, amphoteric oxides and neutral oxides (e.g., CO, NO, N2O).

Sulphur allotropes (S8)

Rhombic (α-S8) and monoclinic (β-S8); transition temperature ~369 K; S8 rings; S2 in vapour shows paramagnetism.

Chlorine (Cl2) properties and uses

Greenish-yellow gas; produced by Deacon’s process or electrolysis; forms HCl and HOCl in water; used for bleaching and in organic synthesis.

Hydrochloric acid (HCl) preparation

Prepared by heating NaCl with concentrated H2SO4; strong acid; NH3 + HCl gives NH4Cl.

Xenon fluorides and hydrolysis

XeF2, XeF4, XeF6; hydrolyse to XeO3 and XeO2F2; powerful fluorinating agents; XeF2 forms [XeF]+ with PF5.

Reaction trends in halogens

Reactivity decreases down the group; F2 is the strongest oxidising agent; interhalogens are generally more reactive than halogens (except F).

Summary theme

Group 15-18 p-block elements show diverse chemistry: variations in oxidation states (notably +3/+5 for Group 15), allotropy (P, S), interhalogens, oxoacids, and noble gas chemistry under special conditions.