Chemical Properties of Elements In S Block

Elements of first group A and second group in the periodic table are called s block elements. First group elements include Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium and Francium. These first group elements except Hydrogen are called Alkali metals. This is because when these metals or their oxides are dissolved in water, they form alkaline solution.

Second group elements include Beryllium, Magnesium, Calcium, Strontium, Barium and Radium. Second group elements are called Alkaline earth metals. When these metals are dissolved in water, they form alkaline solution. Now we shall discuss the reactions of s block elements with oxygen. Oxygen is in Six A group of the periodic table. It is a non-metal and highly electronegative.

When Hydrogen reacts with oxygen, it forms water. Two hydrogen molecules react with one molecule of oxygen to form two molecules of water.When we cut the Alkali metals, they appear shiny. But after some time, they become dull. This is called tarnishing. This is because these metals react rapidly with oxygen in the air and form oxides.Lithium forms lithium oxide, sodium forms sodium oxide and potassium forms potassium oxide. In the same way oxides of Rubidium, cesium and francium are also formed when they react with oxygen. These reactions are illustrated.

Second group elements are alkaline earth metals. These react with oxygen and form oxides. They do not react with oxygen as rapidly as alkali metals.Beryllium reacts with oxygen to form Beryllium oxide. Magnesium reacts with oxygen to form Magnesium oxide. Calcium reacts with oxygen to form Calcium oxide. Strontium reacts with oxygen to form Strontium oxide. Barium reacts with oxygen to form Barium oxide. These elements also form peroxides which have formula M2O2 . M stands for metals.

S block elements also react with water to form hydroxides. S block elements except hydrogen form alkaline solution when they react with water.Elements of group 1A including Lithium, Sodium, Potassium, Cesium, and francium, react with water to form hydroxides and hydrogen gas.Lithium reacts vigorously with water. This reaction is highly exothermic. Heat is emitted in this reaction along with the formation of lithium hydroxide and hydrogen gas. In the same way sodium and potassium react with water.

Reaction of lithium, sodium and potassium with water is highly exothermic. A lot of heat is evolved during the reaction. Final solution after the reaction is alkaline in nature.Hydrogen gas does not react with water.

Alkaline earth metals react with water to form alkaline solution.All elements of group 2A except Beryllium react with water. Beryllium does not react with water. This is due to high ionization energy of beryllium as compared to other elements in the group. It does not ionize easily. Magnesium, calcium, Strontium, and Barium, react with water to form hydroxides. The resulting solution is alkaline in nature.

S block elements except hydrogen react with acids to form salt and hydrogen gas. For example, the reaction of Lithium metal with hydrochloric acid produces Lithium chloride and water. Lithium chloride is a salt.In the same way, Beryllium, Magnesium, calcium and Strontium react with acids to form salt and hydrogen gas. The reaction of Calcium and Magnesium metals with sulphuric acid to form salts are illustrated.

Among the first group elements in s block, only hydrogen and lithium react with nitrogen to form stable compounds. Hydrogen reacts with nitrogen to form Ammonia. It is an exothermic reaction. Heat is released during the process.Lithium reacts with nitrogen to form Lithium nitride Li3N . Lithium nitride is stable.

All the second group elements in s block except Beryllium react with nitrogen to form nitrides. Beryllium does not form nitride. This is because it does not provide enough lattice energy to convert stable nitrogen molecule into nitride ion N-3 ion .The formation of Magnesium nitride, Calcium nitride, Strontium nitride and Barium nitride is illustrated.

Alkali and alkaline earth metals which are also called s block elements react with hydrogen to form metal hydrides. For example, Lithium reacts with hydrogen to form Lithium hydride. In the same way sodium, potassium, calcium, beryllium, Magnesium, strontium and barium also react with hydrogen to form hydrides. The reaction of some of these metals with hydrogen is illustrated.

There are a lot of similarities in chemical properties and reactions between first group and second group elements. Both first group elements and second group elements excluding hydrogen are metals. First group elements have one electron in their valence shell. Second group elements have two electrons in their valence shell. This shows that they can undergo loss of electrons easily. That is why except hydrogen they react readily with acids forming salt and hydrogen gas. They are highly electropositive. This shows that they can react with highly electronegative elements.

Their reactions are mostly exothermic. These elements are mostly highly reactive.For example, when sodium or lithium metal is dissolved in water, the reaction is highly exothermic. A lot of amount of heat is released. These metals also readily react with oxygen in air.Reaction of sodium metal with water is illustrated.

Alkali metals have one electron in their valence shall. This means that when they undergo loss of one electron, they achieve nearest noble gas configuration. Their cations are stable.For example, when lithium undergoes the loss of one electron, it forms lithium cation Li+ ion . Now this cation has two electrons which is equal to the number of electrons in helium atom. Lithium ion Li+ ion is stable.

In the same way elements of group two have two electrons in their valence shell. They can undergo loss of those two electrons easily to form a divalent cation M+2 . Here M stands for alkaline earth metal.For example, Magnesium atom can undergo loss of two electrons to form a stable cation Mg+2 ion . This Magnesium cation has total of ten electrons. This is equal to the number of electrons in the Neon gas. Neon is a noble gas.