P-Block Elements Vocabulary Flashcards

Vocabulary flashcards covering key terms, minerals, oxoacids, and allotropes from Group 15 to Group 18 p-Block elements.

Pnictogens

Group-15 elements, so named because they produce suffocating or choking effects.

Chile Saltpetre

Sodium nitrate ($\text{NaNO}_3$), occurring as a mineral deposit in the earth's crust.

Indian Saltpetre

Potassium nitrate ($\text{KNO}_3$), an inorganic salt found in the earth's crust.

Inert Pair Effect

The reluctance of valence s-electrons to participate in bonding in heavier p-block elements, leading to higher stability of lower oxidation states such as $+3$ in Group 15 and $+4$ in Group 16.

White Phosphorus

A poisonous, translucent white waxy solid consisting of discrete tetrahedral $\text{P}_4$ molecules with an angle strain of $60^\text{o}$, soluble in $\text{CS}_2$, and capable of glowing in the dark via chemiluminescence.

Red Phosphorus

An odourless, non-poisonous, polymeric form of phosphorus consisting of chains of $\text{P}_4$ tetrahedra, prepared by heating white phosphorus at $573\,K$ in an inert atmosphere.

$\alpha$-Black Phosphorus

An opaque monoclinic or rhombohedral crystalline form of phosphorus prepared by heating red phosphorus in a sealed tube at $803\,K$, which sublimes in air and does not oxidise in air.

$\beta$-Black Phosphorus

A form of phosphorus prepared by heating white phosphorus at $473\,K$ under high pressure, which does not burn in air up to $673\,K$.

Hypophosphorous Acid

Also known as phosphinic acid ($\text{H}_3\text{PO}_2$), a monobasic acid containing one $\text{P-OH}$ bond and two $\text{P-H}$ bonds, exhibiting strong reducing properties.

Phosphorous Acid

Also known as phosphonic acid ($\text{H}_3\text{PO}_3$), a dibasic acid containing two $\text{P-OH}$ bonds and one $\text{P-H}$ bond.

Orthophosphoric Acid

$\text{H}_3\text{PO}_4$, a tribasic acid possessing three $\text{P-OH}$ bonds and zero $\text{P-H}$ bonds.

Chalcogens

Group-16 elements, derived from a Greek term meaning ore-forming elements.

Transition Temperature of Sulphur

$369\,K$, the specific temperature at which both rhombic ($\alpha$-sulphur) and monoclinic ($\beta$-sulphur) allotropic forms are simultaneously stable.

Cyclo-$\text{S}_6$

An allotropic modification of sulphur comprising rings of 6 sulphur atoms that adopt a chair conformation with a bond length of $205\,pm$.

$\text{S}_2$ Molecule

The dominant paramagnetic species of sulphur present at elevated temperatures (approx. $1000\,K$), analogous in magnetic properties to $\text{O}_2$.

Caro's Acid

Peroxymonosulphuric acid ($\text{H}_2\text{SO}_5$), a sulphur oxoacid containing a peroxo ($\text{O-O}$) bond.

Marshall's Acid

Peroxydisulphuric acid ($\text{H}_2\text{S}_2\text{O}_8$), an oxoacid of sulphur containing a peroxo ($\text{O-O}$) linkage.

Oleum

Pyrosulphuric acid or disulphuric acid ($\text{H}_2\text{S}_2\text{O}_7$), formed by combining sulphuric acid with sulphur trioxide.

Halogens

Group-17 elements, derived from the Greek halo meaning salt and genes meaning born, together meaning salt producers.

Carnallite

A hydrated potassium magnesium chloride salt with the formula $\text{KCl} \cdot \text{MgCl}_2 \cdot 6\text{H}_2\text{O}$.

Interhalogen Compounds

Covalent, diamagnetic molecules formed between two different halogens with general formulas $\text{XX'}$, $\text{XX'}_3$, $\text{XX'}_5$, and $\text{XX'}_7$, where $\text{X}$ is the larger, more electropositive halogen.

Noble Gases

Group-18 elements (He, Ne, Ar, Kr, Xe, Rn) characterized by fully filled valence shells ($ns^2 np^6$ except He $1s^2$), high ionization enthalpies, and extremely low chemical reactivity.

Pnictogens

Group-15 elements, so named because they produce suffocating or choking effects.

Group 15 Elemental Metallic Character Trend

Nitrogen ($\text{N}$) and phosphorus ($\text{P}$) are non-metals; arsenic ($\text{As}$) and antimony ($\text{Sb}$) are metalloids; bismuth ($\text{Bi}$) is a typical metal.

Chile Saltpetre

Sodium nitrate ($\text{NaNO}_3$), an inorganic mineral deposit found in the earth's crust.

Indian Saltpetre

Potassium nitrate ($\text{KNO}_3$), an inorganic salt occurring in the earth's crust.

Valence Electronic Configuration of Group 15 Elements

$ns^2 np^3$, featuring a half-filled, extra stable valence subshell containing $5$ valence electrons.

Group 15 Covalent Radii Trend

Increases down the group ($\text{N} < ext{P} < ext{As} < ext{Sb} < ext{Bi}$), with a small increase from $\text{As}$ to $\text{Bi}$ due to poor shielding by filled $d$ and/or $f$ orbitals.

Group 15 Ionisation Enthalpy Comparison

Group 15 elements have higher ionisation enthalpy than Group 14 (due to smaller size) and Group 16 (due to extra stability of half-filled $np^3$ configuration).

Group 15 Electronegativity Order

$$\text{N} > ext{P} > ext{As} > ext{Sb} = ext{Bi}$$

Group 15 Melting Point Trend

Increases up to arsenic ($\text{As}$) and then decreases down to bismuth ($\text{Bi}$): $\text{N} < ext{P} < ext{Bi} < ext{Sb} < ext{As}$.

Group 15 Boiling Point Trend

Increases steadily down the group with an anomaly at bismuth: $\text{N} < ext{P} < ext{As} < ext{Bi} < ext{Sb}$.

Inert Pair Effect

The reluctance of valence s-electrons to participate in bonding in heavier p-block elements, leading to higher stability of lower oxidation states such as $+3$ in Group 15, $+4$ in Group 16, and $+5$ in Group 17.

Stability Trend of Oxidation States in Group 15

The stability of the $+5$ oxidation state decreases down the group, whereas the stability of the $+3$ oxidation state increases due to the inert pair effect ($\text{Bi}^{3+} > ext{Bi}^{5+}$).

Bismuth(V) Fluoride ($\text{BiF}_5$)

The only well-characterised compound of bismuth in the $+5$ oxidation state.

Disproportionation of Nitrous Acid ($\text{HNO}_2$)

In acidic solution, $+3$ oxidation state disproportionates to $+5$ and $+2$: 3 ext{HNO}2 ightarrow ext{HNO}3 + ext{H}_2 ext{O} + 2 ext{NO}.

Disproportionation of Phosphorous Acid ($\text{H}<em>3 ext{PO}</em>3$)

Upon heating, $+3$ oxidation state disproportionates to $+5$ and $-3$: 3 ext{H}3 ext{PO}3
ightarrow ext{H}3 ext{PO}4 + ext{PH}_3.

Maximum Covalency of Nitrogen

$4$, restricted because of the absence of vacant $d$ orbitals in its second valence shell.

Nitrogen Bond Enthalpy

$941.4Shows a very high bond dissociation enthalpy of \,kJ\,mol^{-1}$ due to the presence of a $p\frac{1}{2}-p\frac{1}{2}$ triple bond ($\text{N}\ ext{equiv} ext{N}$).

Comparison of Single N-N and P-P Bond Energy

The single $\text{N-N}$ bond is weaker than the single $\text{P-P}$ bond due to high interelectronic repulsion between non-bonding electrons in the small $\text{N}$ atom, leading to weaker catenation.

Group 15 Hydrides ($\text{EH}_3$) Thermal Stability Trend

Decreases down the group due to increasing $\text{E-H}$ bond length: $\text{NH}<em>3 > ext{PH}</em>3 > ext{AsH}<em>3 > ext{SbH}</em>3 > ext{BiH}_3$.

Group 15 Hydrides ($\text{EH}_3$) Reducing Character Trend

Increases down the group as $\text{E-H}$ bond dissociation enthalpy decreases: $\text{NH}<em>3 < ext{PH}</em>3 < ext{AsH}<em>3 < ext{SbH}</em>3 < ext{BiH}_3$.

Group 15 Hydrides ($\text{EH}_3$) Basicity Order

Decreases down the group due to increasing central atom size and decreasing electron density: $\text{NH}<em>3 > ext{PH}</em>3 > ext{AsH}<em>3 > ext{SbH}</em>3 > ext{BiH}_3$.

Group 15 Hydrides ($\text{EH}_3$) Boiling Point Trend

$\text{PH}<em>3 < ext{AsH}</em>3 < ext{NH}<em>3 < ext{SbH}</em>3 < ext{BiH}<em>3$ ($\text{NH}</em>3$ has higher boiling point than $\text{PH}<em>3$ and $\text{AsH}</em>3$ due to intermolecular hydrogen bonding).

Drago's Rule in Group 15 Hydrides

Explains why $\text{PH}<em>3$, $\text{AsH}</em>3$, and $\text{SbH}_3$ have bond angles near $90^ ext{o}$: the lone pair resides in an almost pure s-orbital with zero hybridisation.

Group 15 Oxides Acidic Strength Trend

Acidic character decreases down the group ($\text{N}<em>2 ext{O}</em>3, ext{P}<em>2 ext{O}</em>3$ acidic; $\text{As}<em>2 ext{O}</em>3, ext{Sb}<em>2 ext{O}</em>3$ amphoteric; $\text{Bi}<em>2 ext{O}</em>3$ basic) and increases with higher oxidation state ($\text{E}<em>2 ext{O}</em>5 > ext{E}<em>2 ext{O}</em>3$).

Neutral Oxides of Nitrogen

Dinitrogen monoxide ($\text{N}_2 ext{O}$) and Nitrogen monoxide ($\text{NO}$), both of which are colourless gases.

Nitrogen Dioxide ($\text{NO}_2$)

An acidic, brown-coloured gas containing an odd electron that readily dimerises to colourless $\text{N}<em>2 ext{O}</em>4$.

Structure of Dinitrogen Pentoxide ($\text{N}<em>2 ext{O}</em>5$)

An acidic, colourless solid lacking any $\text{N-N}$ bond and featuring a planar $\text{O}<em>2 ext{N-O-NO}</em>2$ structure.

Nitrogen Halides Stability

Nitrogen forms no pentahalides; among trihalides, only $\text{NF}<em>3$ is stable while $\text{NCl}</em>3$, $\text{NBr}<em>3$, and $\text{NI}</em>3$ are unstable/explosive.

Phosphorus Pentachloride ($\text{PCl}_5$) Solid State Structure

An ionic solid consisting of tetrahedral $\text{[PCl}<em>4 ext{]}^+$ ($sp^3$ hybridised) cations and octahedral $\text{[PCl}</em>6 ext{]}^-$ ($sp^3d^2$ hybridised) anions.

White Phosphorus

A poisonous, translucent white waxy solid consisting of discrete tetrahedral $\text{P}<em>4$ molecules with an angle strain of $60^ ext{o}$, soluble in $\text{CS}</em>2$, and capable of glowing in the dark via chemiluminescence.

Reaction of White Phosphorus with Boiling NaOH

Disproportionation reaction producing phosphine gas and sodium hypophosphite: \text{P}4 + 3 ext{NaOH} + 3 ext{H}2 ext{O}
ightarrow ext{NaH}2 ext{PO}2 + ext{PH}_3.

Phosphorus Decoxide ($\text{P}<em>4 ext{O}</em>{10}$) Structural Bonding

Consists of $6$ $\text{P-O}$ single bridge bonds, $4$ $\text{P=O}$ terminal double bonds, and $0$ $\text{P-P}$ bonds.

Red Phosphorus

An odourless, non-poisonous, polymeric form of phosphorus consisting of chains of $\text{P}_4$ tetrahedra, prepared by heating white phosphorus at $573\,K$ in an inert atmosphere.

$\alpha$-Black Phosphorus

An opaque monoclinic or rhombohedral crystalline form prepared by heating red phosphorus in a sealed tube at $803\,K$, which sublimes in air and does not oxidise in air.

$\beta$-Black Phosphorus

A crystalline form prepared by heating white phosphorus at $473\,K$ under high pressure, which does not burn in air up to $673\,K$.

Phosphorus Allotropes Reactivity and Stability Orders

Reactivity: White > Red > Black; Stability: Black > Red > White.

Hypophosphorous Acid

Also known as phosphinic acid ($\text{H}<em>3 ext{PO}</em>2$), a monobasic acid containing one $\text{P-OH}$ bond and two $\text{P-H}$ bonds, exhibiting strong reducing properties.

Phosphorous Acid

Also known as phosphonic acid ($\text{H}<em>3 ext{PO}</em>3$), a dibasic acid containing two $\text{P-OH}$ bonds and one $\text{P-H}$ bond.

Orthophosphoric Acid

$\text{H}<em>3 ext{PO}</em>4$, a tribasic acid possessing three $\text{P-OH}$ bonds and zero $\text{P-H}$ bonds.

Reducing Power of Phosphorus Oxoacids

Depends on the number of $\text{P-H}$ bonds present in the acid: $\text{H}<em>3 ext{PO}</em>2 > ext{H}<em>3 ext{PO}</em>3 > ext{H}<em>3 ext{PO}</em>4$.

Acidic Strength Order of Phosphorus Oxoacids

$\text{H}<em>3 ext{PO}</em>2 > ext{H}<em>3 ext{PO}</em>3 > ext{H}<em>3 ext{PO}</em>4$, determined by the comparative stability of their conjugate bases.

Chalcogens

Group-16 elements, derived from a Greek term meaning ore-forming elements.

Abundance of Oxygen

The most abundant element on earth, forming $46.6\%$ by mass of the earth's crust and $20.95\%$ by volume of dry air.

Sulphates Minerals of Sulphur

Gypsum ($\text{CaSO}<em>4 ext{\cdot}2 ext{H}</em>2 ext{O}$), Epsom salt ($\text{MgSO}<em>4 ext{\cdot}7 ext{H}</em>2 ext{O}$), and Baryte ($\text{BaSO}_4$).

Sulphide Ores of Sulphur

Galena ($\text{PbS}$), Zinc blende ($\text{ZnS}$), and Copper pyrites ($\text{CuFeS}_2$).

Group 16 Electron Gain Enthalpy Anomaly

Oxygen has a less negative electron gain enthalpy than sulphur due to its extremely small size and high electron-electron repulsion in the compact $2p$ subshell: $\text{S} > ext{Se} > ext{Te} > ext{Po} > ext{O}$.

Group 16 Melting and Boiling Point Difference

The large difference between oxygen and sulphur is due to atomicity: oxygen exists as diatomic $\text{O}<em>2$ gas while sulphur exists as polyatomic $\text{S}</em>8$ solid.

Catenation Tendency in Group 16

Follows the single-bond energy order $\text{S-S} > ext{Se-Se} > ext{Te-Te} > ext{O-O}$ ($\text{O-O}$ is weak due to lone-pair repulsions).

Common Oxidation States of Group 16 Elements

$-2, +2, +4, +6$. Stability of $-2$ and $+6$ decreases down the group while $+4$ stability increases due to the inert pair effect.

Oxidation States of Oxygen in Fluorine Compounds

$+2$ in $\text{OF}<em>2$ and $+1$ in $\text{O}</em>2 ext{F}_2$ because fluorine is more electronegative than oxygen.

Group 16 Hydrides ($\text{H}_2 ext{E}$) Thermal Stability Order

Decreases down the group as $\text{H-E}$ bond energy decreases: $\text{H}<em>2 ext{O} > ext{H}</em>2 ext{S} > ext{H}<em>2 ext{Se} > ext{H}</em>2 ext{Te}$.

Group 16 Hydrides ($\text{H}_2 ext{E}$) Acidic Strength Order

Increases down the group due to decreasing $\text{H-E}$ bond dissociation enthalpy: $\text{H}<em>2 ext{O} < ext{H}</em>2 ext{S} < ext{H}<em>2 ext{Se} < ext{H}</em>2 ext{Te}$.

Group 16 Hydrides ($\text{H}_2 ext{E}$) Boiling Point Order

$\text{H}<em>2 ext{S} < ext{H}</em>2 ext{Se} < ext{H}<em>2 ext{Te} < ext{H}</em>2 ext{O}$ ($\text{H}_2 ext{O}$ is highest due to extensive hydrogen bonding).

Reducing Character of Group 16 Dioxides

Decreases from $\text{SO}<em>2$ to $\text{TeO}</em>2$: $\text{SO}<em>2$ is reducing, while $\text{TeO}</em>2$ is an oxidising agent.

Group 16 Hexafluorides

Octahedral ($sp^3d^2$ hybridised) gaseous molecules; $\text{SF}_6$ is exceptionally stable and chemically inert due to steric hindrance.

Group 16 Tetrafluorides Physical States

$\text{SF}<em>4$ is a gas, $\text{SeF}</em>4$ is a liquid, and $\text{TeF}_4$ is a solid; all possess see-saw geometry ($sp^3d$ with 1 lone pair).

Disproportionation of Dimeric Selenium Monohalides

Disproportionate into tetrahalide and elemental selenium: 2 ext{Se}2 ext{Cl}2
ightarrow ext{SeCl}_4 + 3 ext{Se}.

Rhombic Sulphur (a-Sulphur)

A yellow crystalline form stable below $369\,K$ with specific gravity $2.06$, insoluble in water and soluble in $\text{CS}_2$.

Monoclinic Sulphur (eta-Sulphur)

Colourless needle-shaped crystals stable above $369\,K$ with specific gravity $1.98$, soluble in $\text{CS}_2$.

Transition Temperature of Sulphur

$369\,K$, the specific temperature at which both rhombic (a-sulphur) and monoclinic (eta-sulphur) allotropic forms are simultaneously stable.

Crown Shape of S8 Ring

Puckered ring conformation adopted by $\text{S}_8$ in both rhombic and monoclinic sulphur, having $\text{S-S}$ bond length $204\,pm$ and bond angle $107^ ext{o}$.

Cyclo-S6 Allotrope

An allotropic modification of sulphur comprising rings of 6 sulphur atoms that adopt a chair conformation with a bond length of $205\,pm$ and bond angle $102^ ext{o}$.

S2 Molecule

The dominant paramagnetic species of sulphur present at elevated temperatures (approx. $1000\,K$), analogous in magnetic properties to $\text{O}_2$.

Caro's Acid

Peroxymonosulphuric acid ($\text{H}<em>2 ext{SO}</em>5$), a sulphur oxoacid containing a peroxo ($\text{O-O}$) bond.

Marshall's Acid

Peroxydisulphuric acid ($\text{H}<em>2 ext{S}</em>2 ext{O}_8$), an oxoacid of sulphur containing a peroxo ($\text{O-O}$) linkage.

Oleum

Pyrosulphuric acid or disulphuric acid ($\text{H}<em>2 ext{S}</em>2 ext{O}_7$), formed by combining sulphuric acid with sulphur trioxide.

Halogens

Group-17 elements, derived from the Greek halo meaning salt and genes meaning born, together meaning salt producers.

Fluorspar

An insoluble fluoride mineral with formula $\text{CaF}_2$.

Cryolite

An ore of aluminium containing fluorine with the formula $\text{Na}<em>3 ext{AlF}</em>6$.

Carnallite

A hydrated potassium magnesium chloride salt with the formula $\text{KCl} ext{\cdot} ext{MgCl}<em>2 ext{\cdot}6 ext{H}</em>2 ext{O}$.

Electron Gain Enthalpy Order of Halogens

$\text{Cl} > ext{F} > ext{Br} > ext{I}$; Chlorine has the most negative electron gain enthalpy in the periodic table because Fluorine experiences strong electron-electron repulsion in its compact $2p$ orbital.

Halogen Electronegativity Order

$\text{F} > ext{Cl} > ext{Br} > ext{I} > ext{At}$; Fluorine is the most electronegative element in the periodic table.

Physical States and Colors of Halogens

$\text{F}<em>2$ (yellow gas), $\text{Cl}</em>2$ (greenish-yellow gas), $\text{Br}<em>2$ (red-brown liquid), $\text{I}</em>2$ (dark violet solid).

Cause of Halogen Colors

Absorption of light in the visible region causing excitation of outer electrons from highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO).

Bond Dissociation Enthalpy Order of Halogens

$\text{Cl}<em>2 > ext{Br}</em>2 > ext{F}<em>2 > ext{I}</em>2$; $\text{F-F}$ bond energy is unexpectedly low due to lone pair-lone pair repulsions between adjacent small atoms.