write difference between the group IIA elements and group VIA elements
Answers
Answer: - The elements in Group IIA (Be, Mg, Ca, Sr, Ba and Ra) are all metals, and all but Be and Mg are active metals. These elements are often called the alkaline-earth metals. The term alkaline reflects the fact that many compounds of these metals are basic or alkaline. The term earth was historically used to describe the fact that many of these compounds are insoluble in water. Most of the chemistry of the alkaline-earth metals (Group IIA) can be predicted from the behavior of the alkali metals (Group IA). Three points should be kept in mind, however.
The alkaline-earth metals tend to lose two electrons to form M 2+ ions (Be2+, Mg2+, Ca2+, and so on).
These metals are less reactive than the neighboring alkali metal. Magnesium is less active than sodium; calcium is less active than potassium; and so on.
These metals become more active as we go down the column. Magnesium is more active than beryllium; calcium is more active than magnesium; and so on.
The alkaline-earth metals react with nonmetals to give the products expected from the electron configurations of the elements.
Mg(s) + Cl2(g) ----> MgCl2(s)
3 Mg(s) + N2(g) ----> Mg3N2(s)
Ca(s) + H2(g) ----> CaH2(s)
Because they are not as active as the alkali metals, most of these elements form oxides.
2 Mg(s) + O2(g) ----> 2 MgO(s)
Calcium, strontium, and barium can also form peroxides.
Ba(s) + O2(g) ----> BaO2(s)
The more active members of Group IIA (Ca, Sr, and Ba) react with water at room temperature. The products of these reactions are what we might expect. Calcium, for example, loses two electrons to form Ca2+ ions when it reacts with water.
Ca ----> Ca2+ + 2 e-
These electrons are picked up by the water molecules to form H2 gas and OH- ions.
2 H2O + 2 e- ----> H2 + 2 OH-
Combining the two halves of the reaction so that electrons are conserved gives the following result.
Ca(s) + 2 H2O(l) ----> Ca2+(aq) + 2 OH-(aq) + H2(g)
Although Mg does not react with water at room temperature, it will react with steam. The products of this reaction can't be aqueous Mg2+ and OH- ions because there is no liquid water around to stabilize these ions. The products of this reaction are H2 gas and magnesium oxide, MgO.
Mg(s) + H2O(g) ----> MgO(s) + H2(g)
Practice Problem 2:
Magnesium reacts with hydrogen to form compound A, which is a white solid at room temperature. It also reacts with hydrochloric acid to form gas B and an aqueous solution of compound C. Identify the products of these reactions and write balanced equations for each reaction.
Click here to check your answer to Practice Problem 2
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Group IIIA: The Chemistry of Aluminum
The elements in Group IIIA (B, Al, Ga, In, and Tl) can be divided into three classes.
2 Al(s) + 3 Br2(l) ----> Al2Br6(s)
4 Al(s) + 3 O2(g) ----> 2 Al2O3(s)
16 Al(s) + 3 S8(s) ----> 8 Al2S3(s)
Aluminum reacts with concentrated acids to give Al3+ ions and H2 gas.
2 Al(s) + 6 H+(aq) ----> 2 Al3+(aq) + 3 H2(g)
It also reacts with concentrated bases to give H2 gas and the aluminate ion, Al(OH)4-, in which aluminum is in the +3 oxidation state.
2 Al(s) + 2 OH-(aq) + 6 H2O(l) ----> 2 Al(OH)4-(aq) + 3 H2(g)
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Group IVA: Tin and Lead
The elements in Group IVA can be divided into three classes:
carbon, which is a nonmetal;
silicon and germanium, which are semimetals; and
tin and lead, which are metals. Tin and lead are among the oldest metals known.
Tin and lead are much less reactive than any of the groups IA, IIA, or IIIA metals. According to the argument that elements become more metallic -- and therefore more active -- as we go down a column of the periodic table, lead should be more reactive than tin.
Lead reacts with air to form a thin coating of PbO and/or PbCO3, which protects the metal from further reaction.
2 Pb(s) + O2(g) ----> 2 PbO(s)
PbO(s) + CO2(g) ----> PbCO3(s)
When finely divided, lead is pyrophoric -- it bursts into flame in the presence of oxygen.
Tin does not react with either air or water at room temperature. When heated until white hot, tin reacts with air to form SnO2.
Sn(s) + O2(g) ----> SnO2(s)
At high temperatures it also reacts with steam to give SnO2.
Sn(s) + 2 H2O(g) ----> SnO2(s) + 2 H2(g)
Tin and lead are both less active than aluminum. Neither metal reacts with either dilute hydrochloric acid or dilute sulfuric acid at room temperature. Tin, when heated, reacts with either concentrated hydrochloric acid or concentrated sulfuric acid.