(a) both assertion and reason are true and reason is the correct explanation of assertion

(i) \(CaCO_3\xrightarrow{heat}CaO+CO_2\)
(ii) \(CaSO_4.2H_2O\xrightarrow{heat}\underset{Dead\ burnt\ plaster}{CaSO_4}+2H_2O\)

Due to small size, the ionization enthalpies of Be and Mg are much higher than those of other alkaline earth metals. Therefore, a large amount of energy is needed to excite their valence electron and that's why they do not impart colour to the flame.

Calcium oxide (quick lime) is used
(i) to manufacture cement, mortar and glass.
(ii) in the manufacture of sodium carbonate and slaked lime.
(iii) in the purification of sugar.
(iv) as drying agent

Anhydrous calcium sulphate formed by heating plaster of Paris above 393 K is known a dead burnt plaster. It has a remarkable property of setting with water. On mixing adequate quantity of water, it forms a plastic mass that gets into a hard solid in 5 to 15 minutes.

Gypsum crystals are sometimes found to occur in a form that resembles the petals of a flower. This type of formation is referred to as 'desert rose' , as they mostly occur in arid areas or desert terrains.

Calcium hydroxide (Ca(OH)₂) is called slaked lime. It is formed by the addition of limited amount of water as quick lime.
CaO + H₂O ⟶ Ca(OH)₂

(i) CaO + H_2O ⟶ Ca(OH)₂ (Calcium hydroxide)
(ii) CaO + CO₂  ⟶  CaCO₃ (Calcium carbonate)
(iii) CaO + SiO₂ ⟶ CaSiO₃ (Calcium silicate)
(iv) 6CaO + P₄O₁₀ ⟶ 2Ca₃(PO)₄ (Calcium phosphate)

(i) BeSO₄ > MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄.
(ii) Be(NO₃)₂ <  Mg(NO₃)₂ < Ca(NO₃)₂ < Sr(NO₃)₂ < Ba(NO₃)₂ < Ba(NO₃)₂
[due to increase in size of M⁺² ions]

All the properties increase down the group.
Be(OH)₂ < Mg(OH)₂ < Ca(OH)₂ < Sr(OH)₂ < Ba(OH)₂

Beryllium (the first member of group 2) shows a diagonal relationship with aluminium. In this case,the size of these ions (r_Be²⁺= 0.45Å and r_Al³⁺ = 0.54 Å) is not as Close. However, their charge per unit area is closer (Be²⁺ = 2.36 and Al³⁺ = 2.50). They also have same electronegativity values (Be = 1.5; Al = 1.5).

(i) Sodium and potassium ions maintain the ion balance and nerve impulse conduction.
(ii) Transport of sugar and amino acids into cells.
(iii) Potassium ions activate many enzymes, participate in the oxidation of glucose to produce ATP.
(iv) With sodium, potassium ion is responsible for the transmission of nerve signals.
(v) Sodium and potassium pump play an important role in transmitting nerve signals.

This compound is prepared by saturating a solution of sodium carbonate with carbon dioxide. The white crystalline powder of sodium bicarbonate, being less soluble, precipitated out.

2NH₃ + H₂O + CO₂ ⟶ (NH₄)₂ CO₃
(NH₄)₂ CO₃ + H₂O + CO₂ ⟶ 2NH₄ HCO₃
2NH₄HCO₃ + NaCl ⟶ NH₄Cl + NaHCO₃
2NaH CO₃ ⟶ Na₂ CO₃ + CO₂ + H₂O.

The solubility product of NaCl is lower than that of NaOH. The more soluble a substance is, the higher the K_sp value it has In aqueous solution NaOH gives OH^- ions. It can be solvated by establishing H-bonds with water molecules. So it is more water soluble.

2Ca + O₂ ⟶ 2CaO

Mg (OH)₂ ; Magnesium hydroxide.

Efflorescence is the spontaneous loss of water by a hydrated salt, which occurs when the aqueous vapor pressure of the hydrate is greater than the partial pressure of the water vapour in the air. This is the property of salts
Ex: Glauber's salt- Na₂SO₄·10H₂O
Epsom salt - MgSO₄·7H₂O

(i) In solid state

(ii) In vapour state

(iii) At high temperature
\(\underset{Linear\ monomer}{Cl-Be-Cl}\)

Be(OH)₂ is amphoteric in nature as it reacts with both acid and alkali
Be(OH)₂ + 2NaOH ⟶ Na₂BeO₂ + 2H₂O
Acidic
Be(OH)₂ + 2HCI ⟶ BeCl₂ + 2H₂O
Basic

(i) Alkali metals dissolve in liquid ammonia to give deep blue solutions that are conducting in nature.
(ii) This happens because the alkali metal atom readily loses the valence electron in ammonia solution.
(iii) Both the cation and the electron combine with ammonia to form ammoniated cation and ammoniated electron
M + (x +y)NH₃ ⟶ [M(NH₃)_x]⁺ + [e(NH₃)_y]^-

This is because in alkali metals the second electron is to be removed from a cation, which has already acquired a noble gas configuration. In the case of alkaline earth metals, the second electron is to be removed from a monovalent cation, which still has one electron in the outermost shell. Thus, the second electron can be removed more easily in the case of group 2 elements than in group 1 elements.

Sodium hydroxide is prepared commercially by the electrolysis of brine solution in Castner-Kellner cell using a mercury cathode and a carbon anode. Sodium metal is discharged at the cathode and combines with mercury to form sodium amalgam. Chlorine gas is evolved at the anode. The sodium amalgam thus obtained is treated with water to give sodium hydroxide.
At cathode: Na⁺ + e^- ⟶ Na(amalgam)
At anode: Cl^- ⟶ 1/2Cl₂ ↑ + e^-
2Na(amalgam) + 2H₂O ⟶ 2NaOH + 2Hg + H₂↑

In this process, ammonia is converted into ammonium carbonate which then converted to ammonium bicarbonate by passing excess carbon dioxide in a sodium chloride solution saturated with ammonia. The ammonium bicarbonate thus formed reacts with the sodium chloride to give sodium bicarbonate and ammonium chloride. As sodium bicarbonatehas poor solubility, it gets precipitated. The sodium bicarbonate is isolated and is heated to give sodium carbonate. The equations involved in this process are,
2NH₃ + H₂O + CO₂ ⟶ (NH₄)₂CO₃
(NH₄)₂CO₃ + H₂O + CO₂ ⟶ 2NH₄HCO₃
2NH₄HCO₃ + NaCl ⟶ NH₄Cl + NaHCO₃
2NaHCO₃ ⟶ Na₂CO₃ + CO₂ + H₂O
The ammonia used in this process can be recovered by treating the resultant ammonium chloride solution with calcium hydroxide. Calcium chloride is formed as a by-product..

(i) The electropositive character increases from Li to Cs. Hence their ionic character increases down the group.
(a) The stability of the hydrides decreases down the group, as the size of the metal ion increases. The M - H bond distance increases with increase in size of metal ion and it can be readily broken. i.e., the metal hydride is least stable.
(iii) They are powerful reducing agents as M - H bond is weaker and it can be readily broken.

(l) BeO is almost insoluble in water because Be²⁺ is a small cation with high polarising power and O^2- is small anion.
∴ the lattice energy very high.
When BeO is dissolved in water, the hydration energy of its ions is not sufficient to overcome high lattice energy.
(ii) On the other hand, Be²⁺ is a small cation and is a large anion. Hence Be²⁺ can easily polarize, \(SO_4^{2-}\) ions, making BeSO₄ unstable the lattice energy of BeSO₄ is not very high and so it is soluble in water.

Milk of lime reacts with chlorine to form hypochlorite, a constituent of bleaching powder.
2Ca (OH)₂ + 2Cl₂ ⟶ CaCl₂ + Ca(OCI)₂ + 2H₂O

(i) Slaked lime + CO₂ + H₂O ⟶\(\underset{Calcium\ bicarbonate}{Ca(HCO_3)_2}\)
(ii) Quick lime + CO₂ ⟶ \(\underset{Calcium\ bicarbonate}{CaCO_3}\)
(iii) Slaked lime + CO₂ ⟶\(\underset{Calcium\ bicarbonate}{CaCO_3+H_2O}\)
(iv) Be(OH)₂ + HCl + H₂O ⟶\(\underset{Tetra\ hydroxy\ beryllium\ chloride}{[Be(OH)_4]CI_2}\)

Beryllium	Other elements of the family
Forms covalent compounds	Other members form of the group form ionic bonds
High melting and boiling point	Low melting and boiling point
Does not react with water even at elevated temperature	React with water
Does not combine directly with hydrogen	Combine directly with hydrogen
Does not combine directly with halogens	Combine directly with halogens
Halides are covalent	Halides are electrovalent
Hydroxide and oxides of beryllium are amphoteric in nature	Basic in nature
It is not readily attacked by acids because of the presence of an oxide film	Readily attacked by acids

i) Be and Mg atoms are smaller and their electrons being strongly bound to the nucleus are not excited to higher energy level.
ii) Therefore they do not give colour in the flame test

The anomalous properties of beryllium is mainly due to its,
(i) small size,
(ii) high electronegativity,
(iii) high ionization energy and
(iv) high polarizing power compared to. the other elements in the block

The similarity in properties of the first element of each group with the elements to the lower right of the next period ie, diagonally opposite element is known as diagonal relationship.
It is due to
i) similarity in the size of ions
ii) similarity in polarizing power
iii) similarity in electropositive character

(i) Sodium carbonate known as washing soda is used for laundering
(ii) It is an important laboratory reagent used in the qualitative analysis and in volumetric analysis.
(iii) It is also used in water treatment to convert the hard water to soft water
(iv) It is used in the manufacture of glass, paper, paint etc

It is due to weak metallic bonds and large atomic size.

Alkali metals have one e^o in their outer most shell. Alkaline earth metals have 2 e^o in their outer most shell. More valence electrons and more positively charged nucleii leads to greater opportunity for metallic bonding.

In Na₂ SO₄.10 H₂O. So the metal will be Na (sodium). The salt is washing soda.

1. Gypsum is used in making drywalls or plaster boards.
2. Another important use of gypsum is the production of plaster of Paris. Gypsum is heated to about 300 degree Fahrenheit to produce plaster of paris, which is also known as gypsum plaster. It is mainly used as a sculpting material.
3. Gypsum is used in making surgical and orthopedic casts, such as surgical splints and casting moulds.
4. Gypsum plays an important role in agriculture as a soil additive, conditioner, and fertilizer. It helps loosen up compact or clay soil, and provides calcium and sulphur, which are essential for the healthy growth of a plant.
5. Gypsum is used in toothpastes, shampoos, and hair products.
6. Gypsum is a component of portland cement, where it acts as a hardening retarder to control the speed at which concrete sets.

Calcium Sulphate (plaster of paris), CaSO₄. 1/2H₂O :
It is a hemihydrate of calcium sulphate. It is obtained when gypsum, CaSO₄ .2H₂O,is heated to 393 K
2(CaSO₄.2H₂O) ⟶ 2CaSO₄,H₂O + 3H₂O
Above 393 K, no water of crystallisation is left and anhydrous calcium sulphate, CaSO₄ is formed. This is a known 'dead burnt plaster'.
It has a remarkable property of setting with water. on mixing with an adequate quantity of water it forms a plastic mass that gets into hard solid in 5 to 15 minutes.

This is due to the smaller size and relatively high charge as Be²⁺ ion. Moreover Beryllium is a non - metal. But Magnesium is a metal. In the case of beryllium the ionisation energy and electronegativity of the halides are almost similar; but there is a vast difference in IE and electronegativity between Mg and halides.

The largest use of plaster of paris is in the building industry as well as plasters. It is used for immobilising the affected part of organ where there is a bone fracture or sprain. It is also employed in dentistry, in ornamental work and for making casts of statues and busts.

The lattice energy of LiF is higher due to the smaller size of Li⁺ and F^-. So LiF has lower solubility.

	Alkali Metals	Alkaline earth metals
1.	Alkali metals are soft	Alkaline earth metals are hard
2.	They have a single electron in the valence shell and their electronic configuration is [noble gas] ns1.	They have two electrons in the valence shell and their electronic configuration is [noble gas] ns2
3.	They have low melting points	They have relatively high melting points
4.	Hydroxides are strongly basic.	Hydroxides are less basic
5.	Carbonates do not decompose	Carbonates decompose to form oxide, when heated to high temperatures.
6.	Nitrates give corresponding nitrites and oxygen as products.	Nitrates give corresponding oxides nitrogen dioxide and oxygen as products.
7.	They show + 1 oxidation states.	They show +2 oxidation states
8.	Their carbonates are soluble in water except Li2CO3.	Their carbonates are insoluble in water.
9.	Except Li, alkali metals do not form complex compounds.	They can form complex compounds.

(i) Monovalent sodium and potassium ions are found in large proportions in biological fluids.
(ii) These ions perform important biological functions such as maintenance of ion balance and nerve impulse conduction.
(iii) Sodium - Potassium play an important role in transmitting nerve signals.
(iv) A typical 70 kg man has 90 g of Na and 170 g of K.
(v) Sodium ions are found on the outside of cells, being located in blood plasma and in the interstitial fluid which surrounds the cells. These ions .participate in the transmission of nerve signals, in regulating the flow of water across cell membranes and in the transport of sugars and amino acids into cells.
(vi) Potassium ions are the most abundant cations within cell fluids, where they activate many enzymes, participate in the oxidation of glucose to produce ATP and with sodium, are responsible for the transmission of nerve signals.

The anomalous properties of beryllium is mainly due to its small size, high electro negativity, high ionisation energy and high polarising power compared to the other elements in the group. The anomalous properties of beryllium compared to other elements of the group are mentioned in table.

Beryllium	Other elements of the family
Forms covalent compounds	Form ionic compounds
High melting and boiling point	Low melting and boiling point.
Does not react with water even at elevated temperature.	React with water.
Does not combine directly with hydrogen.	Combine directly with hydrogen.
Does not combine directly with halogens Halides are covalent.	Combine directly with halogens. Halides are electrovalent.
Hydroxide and oxides of beryllium are amphoteric in nature.	Basic in nature.
It is not readily attacked by acids because of the presence of an oxide film.	Readily attacked by acids.
Beryllium carbide evolves methane with water	evolve acetylene with water.
Salts of Be are extensively hydrolysed.	Hydrolysed.

(i) An element A belonging to II group and II period is beryllium (A)
(ii)  Beryllium reacts with chlorine to form beryllium chloride (B)
Be +Cl₂ \(\longrightarrow \) BeCl₂
                         (B)
(iii) Beryllium chloride on treatment with LialH Forms beryllium hydride (c)
2BeCl₂ + LiA1H₄ \(\longrightarrow \) 2BeH₂ + LiCl + AlCl₃ 
                                                             (C)

A	Be	Beryllium
B	Becl2	Beryllium Chloride
C	BeH2	Beryllium Hydride

(i) An element belonging to group number I and period number 3 is Sodium
(ii) Sodium, on reaction with a halogen (Cl₂) forms Sodium Chloride (D)
2Na + Cl₂ \(\longrightarrow \) 2NaCl
(iii) Sodium Chloride Reacts with ammonium bicarbonate to give Sodium Bicarbonate and ammonium chloride (c)
2NH₄HCO₃ + NaCl \(\longrightarrow \) NH₄Cl + NaHCO₃
(iv)  Sodium bicarbonate on heating forms sodium carbonate (D)
2NaHCO₃ \(\longrightarrow \) Na₂CO₂ + CO₂ + H₂O

A	NaCl	Sodium chloride
B	NaHCO3	Sodium bicarbonate
C	NH4Cl	Ammonium Chloride
D	Na2CO3	Sodium carbonate

(i) 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. Magnesium plays an important· role in many biochemical reactions catalysed by enzymes. It is the co-factor of all enzymes that utilize ATP in phosphate transfer and energy release. It is also essential for DNA synthesis and is responsible for the stability and proper functioning of DNA.It is also used for balancing electrolytes in our body. Deficiency of magnesium results into convulsion and neuromuscular irritation.
(ii) Calcium is a major component of bones and teeth. It is also present in blood and its concentration is maintained by hormones (calcitonin and parathyroid hormone). Deficiency of calcium in blood causes it to take longer time to clot. It is also important for muscle contraction.
(iii) The main pigment that is responsible for photosynthesis, chlorophyll, contains magnesium which plays an important role in photosynthesis.

1. This group contains Be, Mg, Ca, Sr, Ba & Ra.
2. Except Be all these elements are called as alkaline earth metals because their oxides and hydroxides are alkaline in nature.
3. Beryllium is the rare element and Radium is the rarest (10% rocks) ; Their Occurrence: Be- Beryl; Mg - carnallite; Dolomite Ca - Fluorapatite; Sr - Celestite Ba - Barytes.
4. Radium is radioactive.
5. The general electronic configuration is :
[Noble gas] ns² eg. Be - [He] 2s²
6. On moving down the group the radii increase. Their atomic radii are smaller than alkali metals.
7. They exhibit +2 oxidation state.
8. The ionisation enthalpies are less than p - block elements due to large size. Down the group the ionisation enthalpy decreases.
9. The IE₁ of group 2 elements are greater than group 1 elements.
10. The IE₂ values are higher than that of alkali metals.
11. They are less electro Positive elements than alkali metals.
12. The hydration enthalpy decreases with increase in ionic radii.
13. MgCl₂ form MgCI₂ .6H₂O and CaCl₂ form CaCl₂.6H₂O
14. The electronegativity value decreases down the group.
15. With concentrated HCl They impart flame colour. Ca - Brick Red ; Sr - Crimson red and Barium - Apple Green.
16. All form metallic halides at elevated temperatures. M + X₂ + MX₂
17. All elements except Beryllium combine with hydrogen to form hydrides of formula MH₂.

(i) Alkaline earth metal (A) belonging to 3rd period is magnesium.
(ii) So A is Magnesium. Magnesium reacts with oxygen and nitrogen as follows.
\(2Mg+O_2⟶\underset{(B)}{2MgO}\)
\(3Mg+N_2⟶\underset{(C)}{Mg_3N_2}\)
So B is Magnesium oxide and C is magnesium nitride.
(iii) Magnesium undergoes metal displacement reaction with AgNO₃ as follow to give D as follows :
\(Mg+2AgNO_3⟶\underset{D}{Mg(NO_3)_2}+2Ag\)
So D is Magnesium nitrate.
Result  :

Compound or Element	Symbol or Formula	Name
A	Mg	Magnesium
B	MgO	Magnesium oxide
C	Mg3N2	Magnesium nitride
D	Mg(NO3)2	Magnesium nitrate

S.No	Properties
1	Beryllium chloride forms a dimeric structure like aluminium chloride with chloride bridges. Beryllium chloride also forms polymeric chain structure In addition to dimer. Both are soluble in organic solvents and are strong lewis acids.
2	Beryllium hydroxide dissolves in excess of alkali and gives beryllate ion and [Be(OH)2]2- and hydrogen as aluminium hydroxide which gives aluminate ion, [Al(OH)4]-
3	Beryllium and aluminum ions have strong tendency to form complexes, \(BeF_4^{2-} AIFt{_6^{3-}}\)
4	Both beryllium and aluminium hydroxides are amphoteric in nature.
5	Carbides of beryllium (Be2C) like aluminum carbide (Al4C3) give methane on hydrolysis
6	Both beryllium and aluminium are rendered passive by nitric acid.

Magnesium oxide in having higher melting point. The lattice energy of MgO & MgF₂ are 3938 and 2957 respectively.
MgO has +2, -2 charges, MgF₂ has +2, -1 charges. When the two charges are multiplied together, MgO results in larger amount of lattice energy since it has a higher charge, The strong attraction cause most ionic material to be hard and brittle and have high melting points.