Ch 5Alkali and Alkaline Earth Metals — Class 11 Chemistry, concept-first.

This unit turns to two of the most reactive families in the periodic table: the alkali metals (Group 1) and the alkaline earth metals (Group 2), together called the s-block elements because their oute…

The elements of group 1 and group 2 of the modern periodic table are together called the s-block elements, because in each of them the differentiating (last-entering) electron occupies an s orbital.

The name alkali comes from the Arabic al-qaliy, meaning "the plant ashes" -- the original source from which alkaline substances were obtained.

Occurrence. Alkali metals are so reactive that none of them is found free in nature -- they occur only combined, as compounds.

Although lithium heads group 1, it behaves noticeably differently from the rest of its own family -- a pattern the first member of every group in the periodic table tends to show.

Alkali metals are chemically very reactive. Reactivity increases from Li to Cs, tracking the fall in ionisation energy down the group, and every alkali metal reacts readily with the more electronegati…

- Lithium is alloyed for several specialised uses: with lead, to make the 'white metal' bearings used in motor engines; with aluminium, for aircraft parts; and with magnesium, for armour plate.

All the common compounds of the alkali metals are, as a family, generally ionic in nature -- a direct consequence of how readily these highly electropositive metals give up their single valence electr…

Sodium carbonate, Na₂CO₃·10H₂O (washing soda). One of the most important inorganic industrial chemicals, made by the Solvay process.

Monovalent sodium and potassium ions are found in large proportions in biological fluids, where they perform essential functions such as maintaining ion balance and conducting nerve impulses.

Group 2 of the modern periodic table contains six elements: beryllium, magnesium, calcium, strontium, barium and radium.

Physical state and occurrence. Beryllium is a rare element, and radium is the rarest of all the group-2 elements, occurring only in minute amounts (chiefly as a decay product wherever uranium-bearing…

Just as lithium heads group 1 with distinctive behaviour, beryllium heads group 2 with anomalous behaviour of its own.

The alkaline earth metals are, as a family, less reactive than the alkali metals, though (as with the alkali metals) their reactivity still increases going down the group.

Uses of beryllium. Because of its low atomic number and very low X-ray absorption, beryllium is used to make the radiation windows for X-ray tubes and X-ray detectors, and sample holders in X-ray emis…

For the alkaline earth metals, the dipositive oxidation state (M²⁺) is the sole, predominant valence. Their compounds, like those of the alkali metals, are predominantly ionic -- but less ionic than t…

Preparation. Quick lime, CaO, is produced on a commercial scale by heating limestone in a lime kiln (Figure 5.10) over the temperature range 1070-1270 K: CaCO₃ ⇌ CaO + CO₂.

Preparation. Calcium hydroxide is prepared simply by adding water to quick lime, CaO.

Gypsum beds formed as water evaporated from massive prehistoric sea basins (Figure 5.11): as the water evaporated, the dissolved minerals became concentrated and crystallised out.

Calcium sulphate hemihydrate, CaSO₄·½H₂O, is plaster of Paris. It is obtained by heating gypsum, CaSO₄·2H₂O, to 393 K: 2CaSO₄·2H₂O(s) → 2CaSO₄·½H₂O + 3H₂O.

Magnesium and calcium also play a vital role in biological functions. A typical adult human body contains about 25 g of magnesium and 1200 g of calcium.

- The elements of groups 1 and 2 of the modern periodic table are called s-block elements, since their differentiating electron occupies an s orbital.

The unit's concept map is rooted at "Alkali Metals (Li, Na, K, Rb, Cs)" and branches into three linked strands.

This is the textbook's own end-of-chapter evaluation for the unit, testing material from both the alkali metal and alkaline earth metal halves of the chapter through two question formats.

Sample papers and previous-year board questions for this subject.