Class 11 Chemistry - Chapter Hydrogen NCERT Solutions | What do you understand by (i) electron-d
What do you understand by (i) electron-deficient, (ii) electron-precise, and (iii) electron-rich compounds of hydrogen? Provide justification with suitable examples.
Molecular hydrides are classified on the basis of the presence of the total number of electrons and bonds in their Lewis structures as:
1. Electron-deficient hydrides
2. Electron-precise hydrides
3. Electron-rich hydrides
An electron-deficient hydride has very few electrons, less than that required for representing its conventional Lewis structure e.g. diborane (B2H6). In B2H6, there are six bonds in all, out of which only four bonds are regular two centered-two electron bonds. The remaining two bonds are three centered-two electron bonds i.e., two electrons are shared by three atoms. Hence, its conventional Lewis structure cannot be drawn.
An electron-precise hydride has a sufficient number of electrons to be represented by its conventional Lewis structure e.g. CH4. The Lewis structure can be written as:
Four regular bonds are formed where two electrons are shared by two atoms.
An electron-rich hydride contains excess electrons as lone pairs e.g. NH3.
There are three regular bonds in all with a lone pair of electrons on the nitrogen atom.
More Questions From Class 11 Chemistry - Chapter Hydrogen
- Q:-
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
- Q:-
Compare the structures of H2O and H2O2.
- Q:-
Write chemical reactions to show the amphoteric nature of water.
- Q:-
Arrange the following
(i) CaH2, BeH2 and TiH2 in order of increasing electrical conductance.
(ii) LiH, NaH and CsH in order of increasing ionic character.
(iii) H-H, D-D and F-F in order of increasing bond dissociation enthalpy.
(iv) NaH, MgH2 and H2O in order of increasing reducing property.
- Q:-
Discuss the principle and method of softening of hard water by synthetic ion-exchange resins.
- Q:-
What do you understand by the term “non-stoichiometric hydrides”? Do you expect this type of the hydrides to be formed by alkali metals? Justify your answer.
- Q:-
What is meant by 'demineralised' water and how can it be obtained?
- Q:-
What causes the temporary and permanent hardness of water?
- Q:-
How does H2O2 behave as a bleaching agent?
- Q:-
Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?
Popular Questions of Class 11 Chemistry
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- Q:-
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
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What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
- Q:-
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- Q:-
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4 - Q:-
Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
- Q:-
What is the basic theme of organisation in the periodic table?
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Explain the formation of a chemical bond.
- Q:-
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only. - Q:-
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?
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- Q:-
Explain why cations are smaller and anions larger in radii than their parent atoms?
- Q:-
A photon of wavelength 4 × 10–7 m strikes on metal surface, the work function of the metal being 2.13 eV. Calculate
(i) the energy of the photon (eV),
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The first (ΔiH1) and the second (ΔiH) ionization enthalpies (in kJ mol–1) and the (ΔegH) electron gain enthalpy (in kJ mol–1) of a few elements are given below:
Elements ΔiH1 ΔiH ΔegH I 520 7300 -60 II 419 3051 -48 III 1681 3374 -328 IV 1008 1846 -295 V 2372 5251 +48 VI 738 1451 -40 Which of the above elements is likely to be :
(a) the least reactive element.
(b) the most reactive metal.
(c) the most reactive non-metal.
(d) the least reactive non-metal.
(e) the metal which can form a stable binary halide of the formula MX2, (X=halogen).
(f) the metal which can form a predominantly stable covalent halide of the formula MX (X=halogen)?
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(a) CO2-3
(b) diamond
(c) graphite?
- Q:-
Calculate the wave number for the longest wavelength transition in the Balmer series of atomic hydrogen.
- Q:-
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