Explain the shape of BrF5.
Br-atom has configuration:
1s2, 2s22p6 , 3s23p63d10, 4s24p5
To get pentavalency, two of the p-orbitals are unpaired and electrons are shifted to 4d-orbitals.
In this excited state, sp3d2-hybridisation occurs giving octahedral structure. Five positions are occupied by F atoms forming sigma bonds with hybrid bonds and one position occupied by lone pair, i.e., the molecule as a square pyramidal shape.
Elements X, Y and Z have 4, 5 and 7 valence electrons respectively, (i) Write the molecular formula of the compounds formed by these elements individually with hydrogen, (ii) Which of these compounds will have the highest dipole moment?
What is the effect of the following processes on the bond order in N-, and 02?
(i) N2 → N+2 + e– (ii) 02 → O+2 + e–
Briefly describe the valence bond theory of covalent bond formation by taking an example of hydrogen. How can you interpret energy changes taking place in the formation of dihydrogen?
Which of the following statements are correct about CO32- ?
(a) The hybridization of central atom is sp3.
(b) Its resonance structure has one C – O single bond and two C = O double bonds.
(c) The average formal charge on each oxygen atom is 0.67 units.
(d) All C – O bond lengths are equal.
Is there any change in the hybridisation ofB and N atoms as a result of the following reaction ? BF3 + NH3 ——-> F3 B.NH3
(a) How many a and n bonds are present in
(b) Why Hf is more stable than H2?
(c) Why is B2 molecule paramagnetic?
Which of the following statements are not correct?
(a) NaCl being an ionic compound is a good conductor of electricity in the solid state.
(b) In canonical structures there is a difference in the arrangement of atoms.
(c) Hybrid orbitals form stronger bonds than pure orbitals.
(d) VSEPR theory can explain the square planar geometry of XeF4.
Match the items given in Column I with examples given in Column II.
| Column I | Column II |
| (i) Hydrogen bond | (a) C |
| (ii) Resonance | (b) LiF |
| (iii) Ionic solid | (c) H2 |
| (iv) Covalent solid | (d) HF |
| (e) 03 |
Why does type of overlap given in the following figure not result in the bond formation?
In which of the following substances will hydrogen bond be strongest?
(a) HCl
(b) H20
(c) HI
(d) H2S
What is an ionic bond? With two suitable examples explain the difference between an ionic and covalent bond?
Write Lewis structure of the following compounds and show formal charge on each atom. HN03, No2, H2so4
Explain why CO2-3 ion cannot be represented by a single Lewis structure. How can it be best represented?
Which molecule/ion out of the following does not contain unpaired electrons?
(a) N+2
(b) 02
(c) O22-
(d) B2
Match the species in Column I with the bond order in Column II.
| Column I | , . Column II |
| (i) NO | (a) 1.5 |
| (ii) CO | (b) 2.0 |
| (iii) o–2 | (c) 2.5 |
| (iv) 02 | (d) 3.0 |
Diamagnetic species are those which contain no unpaired electrons. Which among the following are diamagnetic?
(a) N2
(b) N22-
(c) 02
(d) o22-
Match the species in Column I with the geometry/shape in Column II.
| Column I | Column II |
| (i) H30+ | (a) Linear |
| (ii) HC = CH | (b) Angular |
| (iii) Cl0–2 | (c) Tetrahedral |
| (iv) NH+4 | (d) Trigonal bipyramidal |
| – | (e) Pyramidal |
Use Lewis symbols to show electron transfer between the following atoms to form cations and anions (a) K and S (b) Ca and O (c) Al and N.
Arrange the bonds in order of increasing ionic character in the molecules: LiF, K2O, N2, SO2 and ClF3.
In N0–3 ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are
(a) 2, 2 (b) 3, 1 (c) 1,3 (d) 4, 0
Predict the shapes of the following molecules on the basis of hybridization. BC13, ch4, co2, nh3
Assertion (A): Among the two O – H bonds in H20 molecule, the energy required to break the first O – H bond and other O – H bond is the same.
Reason (R): This is because the electronic environment around oxygen is the same even after breakage of one O – H bond.
(a) A and R both are correct, and R is the correct explanation of A.
(b) A and R both are correct, but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A and R both are false.
Which hybrid orbitals are used by carbon atoms in the following molecules?
(a) CH3-CH3 (b) CH3-CH = CH2 (c) CH3-CH2-OH (d) CH3-CHO (e) CH3COOH.
Compare the relative stability of the following species and indicate their magnetic properties: O2, O2, O2– (Superoxide),O22- (peroxide)
Explain the diamagnetic behaviour of P2 molecule on the basis of molecular orbital theory.
The energy of σ2pz: molecular orbital is greater than 2px and 2pv molecular orbitals in nitrogen molecule. Write the complete sequence of energy levels in the increasing order of energy in the molecule. Compare the relative stability and the magnetic behaviour of the following species:
N2, N+2, N–2, N22+
Arrange the following bonds ‘in order of increasing ionic character giving reason.
N-H, F-H, C-H and O-H
What is meant by the term average bond enthalpy? Why there is difference in bond enthalpy of O – H bond in ethanol (C2H5OH) and water?
Match the species in Column I with the type of hybrid orbitals in Column II.
| Column I | Column II |
| (i) SF4 | (a) sp3cf |
| (ii) if5 | (b) d2sp3 |
| (iii) NO2+ | (c) sp3 d |
| (iv) NH4 | (d) sp3 |
| (e) sp |