Chapter 8- Chemical Bonding Concepts Prof. Onwuachi
1. Write electron configuration, Lewis dot symbols for carbon and
phosphorous and determine total valence electrons.
C => [He]2s22p2 •Ċ: 4 valence electrons
•
2
3
P => [Ne]3s 3p
: Ρ• 5 valence electrons
•
2. Determine the total valence electrons for atoms with the following
identities.
a) electron configuration 1s22s22p63s23p3 5 valence electrons
b) core configuration of [Ar]4s2 2 valence electrons
c) group IV and period 3 4 valence electrons
3. Draw the Lewis symbols (electron dot symbols) for each of the following
atoms or ions:
Cl
Al3+
O2Ar
N3..
3+
2: Ċl :
[Al]
[: Ő :]
:Är:
[:N:]-3
••
••
••
••
4. Write the chemical formula for the ionic compound formed between
following pairs of elements:
a) Ca and F => CaF2 b)Mg & N Mg3N2
c)Li & O Li2O
d)Barium and Iodine e) Cr3+ and O2BaI2
Cr2O3
5. Write the electron configuration for each of the following ions, and
determine which ones possess noble-gas configurations(obey octet or duet
rule , having a complete outershell).
a) Cl- [Ar]
b) Co3+ [Ar]3d6
c) Co2+ [Ar]3d7
d) Cr3+
e) Ti3+
f) Li+
[Ar]3d3
[Ar]3d1
[He]
6. Determine the one with larger lattic energy (circle one) in each of the
following pairs. (please give a reason)
a) CaO, MgO smaller internuclear distance
b) NaF, MgO
larger ion charge value
c) MgO, MgS smaller internuclear distance
d) Fe2O3 , FeO
larger ion charge value
7. Using the given set of ions and atoms, arrange them in order of increasing
sizes;
a) Fe2+ , Fe, Fe3+ ( Fe3+, Fe2+ , Fe)
b) S2-, Ar, Se2(Ar, S2- , Se2-)
c) Al, Cl-, S2-, K+
(K+, Al, Cl-, S2- )
d) S2-, Cl-, K+, Ca2+ (Ca2+ , K+ , Cl- , S2- )
8. Select the ions or atoms from the following sets that are isoelectronic with
each other;write Y=yes or N=no)
a) S2- , Se2-, Ar No
c) Ca2+, Cl-, S2-, K+ Yes
b) Cl-, Cl, Ar No
d) H-, Li+, He Yes
9. Using only periodic table, select the most electronegative atom in each of
the following
sets: a) As, Si, Ge, Ga
b) Li, Be, B, Al
c) Cl, F, I, Br
10. Using electronegativity table classify the following as ionic, polar covalent,
or non-polar
covalent bonds;
a) H-Br PC
b) K-H PC
c) Na-I PC
d) Br-Br NPC
e) N-H PC
11. Which of the following bonds are polar? (circle the more polar or more
electronegative one)
a) B-Cl
b) P-F
c) Br-Cl
d) O-Br
e) Hg-Sb
f) N-H, C-H, O-H
g) I-F, Br-Cl, I-Br
12. Draw Lewis dot structures for the following, and identify those that do not
obey octet rule. (Please draw all resonance structures if any)
a) CH3••
[ H - C - H ]H
b) CH3+
[ H - C - H ]+
H
c) SO3
You do c & d
d) SO32
13. Determine the formal charge of each atom in each of the followings;
∙∙
∙∙
a)[ :N = C= S: ]-
N(-),C(0), S(0)
..
:Cl:
b) [ :C ≡ N: ]-
C(-), N(0)
∙∙
c) S = Si
∙∙
H
S(0), Si(0), H(0), Cl(0)
14. Using the bond enthalpies table (bond dissociation energies in KJ/mol),
estimate
enthalpy change for each of the following gas-phase reactions:
H H
H H
a) H - C - C - O - H (g)  H - C - O - C - H (g)
H H
H H
[5D(C-H) + D(C-C) + D(C-O) + D(O-H)] –[4D(C-H) + 2D(O-H) + 2D(C-O)]
∆H = (3234) – (3294) = -60 kJ
H
H
b) H - C - N  C  H - C - C  N
H
H
[3D(C-H) + D(C-N) + D(C  N)] – [3D(C-H) + D(C-C) + D(C  N)]
∆H = (293) – (348) = -55 kJ
c) C2H4 (g) + 3 O2 (g)  2 CO2 (g) + 2 H2O (g)
{4D(C-H) + D(C = C) + 3D(O=O)} – {4D(C=O) + 4D(O-H)}
∆H = {3150} – {5048) = -1898 kJ