Test Review Chapter 12 chemical bonds
Test - June 3
What is a chemical bond?
A force that holds two or more atoms together and enables them to function as a unit
What does the bond energy of a chemical bond represent?
The energy required to break the bond
What is electronegativity?
The relative ability of an atom in a molecule to attract electrons to itself
What are the three types of bonds we studied? Describe each type of bond.
Ionic – transfer of e-
polar covalent- unequal sharing of e- covalent- equal sharing of e-
Which element is most electronegative?
K, Na, H
F, Br, Na
B, N, F
Rb, Sr, I
Indicate what type of bond forms in each of the following – use electronegativity difference.
O-O covalent
Al – O ionic 2.0 B- O polar covalent 1.5
Br – Cl polar covalent .2
K – Cl ionic 2.2
Cl – Cl covalent
Which of the following molecules contains a polar covalent bond?
H2O
CO F2
N2
C2H6
H-O 1.4 yes / C-O 1.0 yes / F-F 0 / N-N 0 / C-H .4 yes C-C 0 no
Which pair has the more polar bond?
H-F 1.9 or H-Cl .9
O-Cl .5 or O-Br .7
H-Cl .9 or H-I .4
H-Br .7 or H-Cl .9
H-I .4 or H-Br .7
P-S .4 or P-O 1.4
What types of elements react to form an ionic bond?
Metals and non-Metals
What are some characteristics of ionic compounds? High melting point, form electrolytes in water, form
crystal lattice, conduct current when melted
Which bond in each of these pairs has the greater ionic character?
Na-F 3.1 or Na-I 1.6
Ca-S 1.5 or Ca-O 2.5
Li-Cl 2.0 or Cs-Cl 2.3
Mg-N 1.8 or Mg-P .9
For each of these molecules – which end is negative relative to the other end?
HCl
CO
BrF
ClF
ICl
B-C
Si-C
What is the dipole moment? When an atom has a center of negative charge and a center of positive
charge. How is it drawn? Show it for S-Cl +----
What does it mean to say that in forming bonds and stable compounds, atoms try to achieve an electron
configuration like a noble gas? They will transfer, accept, or share e-
What do metals do to form ions? LOSE ELECTRONS Non-metals? GAIN ELECTRONS
Which simple ion would each of the following form? What noble gas has an electron configuration like
it?
Cl z=17 Cl 1- Ar
Sr z=38 Sr 2+ Kr
O z=8 O 2- Ne
rubidium z=37 Rb1+ Kr
For each of the following give a positive ion that would have that many electrons and write the
complete electron configuration for the ion. 1s 2s 2p 3s 3p 4s 3d
10 electrons
1s2 2s2 2p6
18 electrons
Na 1+
1s2 2s2 2p6 3s2 3p6
K 1+
For each of the following give a negative ion that would have that many electrons and write the
complete electron configuration for the ion. 1s 2s 2p 3s 3p 4s 3d
10 electrons
1s2 2s2 2p6
18 electrons
F 1-
1s2 2s2 2p6 3s2 3p6
Cl 1-
Which of the following has an ionic bond?
CO2
CaBr2
HBr
Cl2
NaCl
rule: metal + nonmetal ( 1.9 may not be met)
Why are valence electrons of an atom the ones likely involved in bonding to other atoms?
They are at the outer “edge” of the atom
What does octet mean and why is there an octet rule in writing Lewis structures?
Octet means 8. To form stable compounds atoms (except H) seek to achieve the same number of
valence e- as the noble gases - 8. Putting 8 dots (a line represents 2 dots) puts the atom in the right
configuration with the right number of bonds.
How many electrons are involved when two atoms in a molecule are connected by a double bond? 4
Write the simple Lewis structure for each of the following atoms
Xe 8 dots
Br 7 dots
O 6 dots
Na 1 dot
Mg 2 dots
Al 3 dots
Give the total number of valence electrons in each of the following molecules:
H2O 8
CO 10
F2 14
N2 10
C2H6 14
C4H10 26
Write a Lewis structure for each of the following compounds
H-I 6 dots on I
Cl – P- Cl 6 dots on each Cl 2 dots on P
\Cl
H\
/H
Cl\
Si
H/
Cl/
C
\H
No dots
Cl/
Cl \
6 dots on each Cl
H-O-H 4 dots on O