Group 2 Elements - Reactions, Trends, and Thermal Decomposition (AS Level Chemistry)

A comprehensive set of practice flashcards covering Group 2 elements: reactions, trends, solubility, and thermal decomposition.

Which elements are in Group 2 of the periodic table (the alkali earth metals)?

Be, Mg, Ca, Sr, and Ba.

How many electrons are in the outermost shell of Group 2 elements?

Two electrons.

What is the common oxidation state of Group 2 elements in compounds?

+2 (they donate two outer electrons to form M2+).

How does the reactivity of Group 2 elements change down the group and why?

Reactivity increases down the group due to decreasing ionization energy.

What are the main physical trends for Group 2 elements down the group?

Atomic radius increases; melting point decreases; density increases.

What are the products when Group 2 metal M reacts with oxygen?

M forms MO; Sr and Ba can form MO2 (superoxide).

What are the products when a Group 2 metal M reacts with dilute hydrochloric acid?

MCl2 and H2 gas.

What are the products when a Group 2 metal M reacts with dilute sulfuric acid, and what is special about CaSO4, SrSO4, BaSO4?

MSO4 and H2 gas; CaSO4, SrSO4 and BaSO4 are insoluble.

What happens when Group 2 metals react with water?

M + H2O → M(OH)2 + H2; Be does not react with water; Mg reacts with steam to form MgO and H2.

Which Group 2 oxide is amphoteric?

BeO (beryllium oxide) is amphoteric.

What is the trend for Group 2 oxides when reacting with water (alkalinity)?

They form alkaline solutions; pH increases down the group (BeO is an exception as amphoteric).

What are the products when Group 2 oxides react with dilute acids?

MO + HCl → MCl2 + H2O; MO + H2SO4 → MSO4 + H2O; surface sulfates can form, impeding reaction, especially if oxide is not powdered.

What are the products when Group 2 hydroxides react with dilute acids?

M(OH)2 + HCl → MCl2 + H2O; M(OH)2 + H2SO4 → MSO4 + H2O.

What are the products when Group 2 carbonates react with dilute acids?

MCO3 + HCl → MCl2 + H2O + CO2; MCO3 + H2SO4 → MSO4 + H2O + CO2; BeCO3 is insoluble in water; with HCl carbonates form soluble chloride salts; Ca/Sr/Ba carbonates can form an insoluble sulfate layer with H2SO4, halting the reaction.

Are all Group 2 carbonates soluble in water?

No. All Group 2 carbonates are insoluble in water except BeCO3.

What are the products of the thermal decomposition of Group 2 carbonates?

MCO3(s) → MO(s) + CO2(g).

What are the products of the thermal decomposition of Group 2 nitrates?

M(NO3)2(s) → MO(s) + NO2(g) + O2(g).

Why does thermal stability of carbonates and nitrates increase down Group 2?

Going down the group, larger ions reduce polarizing power, making the carbonate/nitrate ions more stable and requiring more heat to decomposed; overall, thermal stability increases down the group.

What is the general electronic tendency of Group 2 elements in compounds?

Two outer electrons are donated to form +2 ions in ionic compounds; they act as reducing agents.

What are the key physical trends for atomic radius, melting point, and density down Group 2?

Atomic radius increases; melting point decreases; density increases.

What is the solubility trend for Group 2 hydroxides and for sulfates down the group?

Hydroxides become more soluble down the group (higher pH); sulfates become less soluble down the group (CaSO4, SrSO4, BaSO4 are insoluble).

Are all Group 2 chlorides soluble?

Yes, all Group 2 chlorides are soluble.

What happens when CaCO3, SrCO3, or BaCO3 react with sulfuric acid?

They can form an insoluble sulfate layer on their surface, which stops further reaction after initial effervescence (CO2 release).

What gases are produced when Group 2 nitrates thermally decompose?

NO2 and O2.