Inorganic Chemistry
❤️F - block Tricks ❤️
🐡 Lanthanoides- Sar Par Nadiya Prem Ki Samayi, Yuu Gad-Gad Tab Dil Hua, Aree Tum Be Bhi Lutoge?
🦚(Ce, pa, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)
🐡Actinides -Tumhe PadhaUUU Newspaper, Purane Aam Kam Bike(बिके) , Cafe me Aish Farmate Madonna Larra
🦚(Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, La)
✅Notes on s-Block Elements:
Physical Properties of Alkali Metals:
➖These are soft in nature and can be cut with the help of knife except the lithium.
➖The atoms of alkali metals have the largest size in their respective periods.
➖The first ionization energy of the alkali metals are the lowest as compared to the elements in the other group.
➖The alkali metals show +1 oxidation state.
➖The alkali metals have low values of reduction potential (as shown in table-I) and therefore have a strong tendency to lose electrons and act as good reducing agents.
➖The melting and boiling points of alkali metals are very low because the intermetallic bonds in them are quite weak.
Hydroxides of Alkali Metals:
a)All the alkali metals, their oxides, peroxides and superoxides readily dissolve in water to produce corresponding hydroxides which are strong alkalies.
➖2Na + 2H2O → 2NaOH + H2
➖Na2O + 2H2O 2NaOH
➖Na2O2 + 2H2O → 2NaOH + H2O2
➖2KO2 + 2H2O → 2KOH + H2O2 + O2
b) The basic strength of these hydroxides increases as we move down the group Li to Cs.
c) All these hydroxides are highly soluble in water and thermally stable except lithium hydroxide.
d) Alkali metals hydroxides being strongly basic react with all acids forming salts.
➖NaOH + HCI → NacI + H2O
➖2NaOH + H2 SO4 → Na2SO4 + 2H2O
Halides of Alkali metals:
➖M2O + 2HX → 2MX + H2O
➖MOH + HX → MX + H2O
➖M2CO3 + 2HX → 2MX + CO2 + H2O (M = Li, Na, K, Rb or Cs)
(X = F, Cl, Br or I)
➖ll the alkali metals form ionic (electrovalent) compounds.
➖The alkali metals are good conductors of heat and electricity.
➖Alkali metals (except Li) exhibit photoelectric effect
➖The alkali metals and their salts impart a characteristic colour to flame.
Bond Parameters
1. Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule.
2. The Covalent Radius is measured approximately as the radius of on atom's core which is in contact with the core an adjacent atom in a bonded situation.
3. The vander Walls Radius represents the overall size of atoms which included the valence shell in a non-bonded situation.
4. Bond Angle is defined as the angle between the orbitals containing bonding electron pairs around the central atom in a molecule/ion.
5. Bond Enthalpy is defined as the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state. For polyatomic molecules the term mean or average bond enthalpy is used.
6. Bond Order is given by the number of bonds between the two atoms in a molecule.
7. Isoelectronic molecules and ions have identical bond orders for example F₂ and O₂²- have bond order 1, N₂ CO and NO+ have bond order 3.
8. With increase in bond order, bond enthalpy increases and bond length decreases.
Important Points 🌟 -
1. Sulphurous acid - H2SO3
2. Sulphuric acid - H2SO4
3. Thiosulphuric acid - H2S2O3
4. Peroxymonosulphuric (Caro's acid) - H2SO5 (Peroxide bond)
5. Peroxydisulphuric acid (Marshal's acid) - H2S2O8 (Peroxide bond)
6. Pyrosulphurous acid - H
2S2O8 - (S-S linkage)
7. Pyrosulphuric acid - H2S2O7 (S-O-S linkage)
8. Dithionus acid - H2S2O4
9. Dithionic acid - H2S2O6
10. Polythionic acid - H2(S)11O6 (S-S linkage)
🌀Chemical Properties of Alkali Earth Metals:
1. Reaction with water :
Mg + H2O → MgO + H2
or, Mg + 2H2O → Mg (OH)2 + H2
Ca + 2H2O → Ca(OH)2 + H2
2. Formation of oxides and nitrides
Be + O2 (air) +Δ→ 2BeO
3Be + N2 (air) +Δ → Be3N2
Mg + air + Δ → MgO + Ng3N2
3. Formation of Nitrides
3M + N2 + Δ → M3N2
Be3N2 + Δ → 3Be + N2
Ba3N2 + 6H2O + Δ → 3Ba (OH)2 + 2NH3
Ca3N2 + 6H2O + Δ → 3Ca (OH)2 + 2NH3
4. Reaction with hydrogen:
M + H2 + Δ → MH2
Both BeH2 and MgH2 are covalent compounds having polymeric structures in which H – atoms between beryllium atoms are held together by three
centre – two electron (3C - 2e) bonds as shown below:
5. Reaction with carbon – (Formation of carbides)
When BeO is heated with carbon at 2175 – 2275 K a brick red coloured carbide of the formula Be2C is formed
2BeO +2C \xrightarrow[]{2175 - 2275 K}Be_2C +2CO
It is a covalent compound and react water forming methane.
Be2C + 4H2O → 2Be (OH)2 + CH4
6. Reaction with Ammonia:
Like alkali metal, the alkaline earth metals dissolve in liquid ammonia to give deep blue black solution from which ammoniates [ M (NH3)6 ]2+ can be recovered.
Anamolous Behaviour of Beryllium:
Be is harder than other members of its group.
Be is lighter than Mg.
Its melting and boiling points are higher than those of Mg & other members.
Be does not react with water while Mg reacts with boiling water.
BeO is amphoteric while MgO is weakly basic.
Be forms covalent compounds whereas other members form ionic compounds.
Beryllium carbide reacts with water to give methane whereas carbides of other alkaline earth metals gives acetylene gas.
Be2C + 4H2O → 2Be (OH)2 + CH4
Mg2C2 + 2H2O → Mg (OH)2 + C2H2
CaC2 + 2H2O → Ca (OH)2 + C2H2
Beryllium does not exhibit coordination number more than four as it has four orbitals in the valence shell. The other members of this group has coordination number
Diagonal relationship of Be with Al:
Unlike groups – 2 elements but like aluminium, beryllium forms covalent compounds.
The hydroxides of Be, [Be(OH)2] and aluminium [Al(OH)3] are amphoteric in nature, whereas those of other elements of group – 2 are basic in nature.
The oxides of both Be and Al i.e. BeO and Al2O3 are high melting insoluble solids.
BeCl2 and AlCl3 have bridged chloride polymeric structure.
The salts of beryllium as well as aluminium are extensively hydrolysed.
Carbides of both the metal reacts with water liberating methane gas.
Be2C + 4H2O → 2Be (OH)2 + CH4
AI4C3 + 12H2O → 4Al (OH)3 + 3CH4
The oxides and hydroxides of both Be and Al are amphoteric and dissolve in sodium hydroxide as well as in hydrochloric acid.
BeO + 2HCI → BeCI2 + H2O
BeO + 2NaOH → Na2BeO2 + H2O
Al2O3 + 6HCI → 2AICI3 + H2O
AI2O3 + 2NaOH → 2NaAIO2 + H2O
Like Al, Be is not readily attacked by acids because of the presence of an oxide film.
Calcium Carbonate (CaCO3):
It occurs in nature as marble, limestone, chalk, coral, calcite, etc. It is prepared as a white powder, known as precipitated chalk, by dissolving marble or limestone in hydrochloric acid and removing iron and aluminium present by precipitating with NH3, and then adding ammonium carbonate to the solution; the precipitate is filtered, washed and dried.
CaCl2 + (NH4)2CO3 →CaCO3 + 2NH4Cl
It dissolves in water containing CO2, forming Ca(HCO3)2 but is precipitated from solution by boiling.
CaCO3 + H2O + CO2 ↔️ Ca(HCO3)2
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