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Structure
and bonding
Francine
Taylor-Campbell, Contributor
 |
|
Students of Vauxhall Comprehensive High School perform a skit during World Wetlands
Day 2006 celebrations at the University of the West Indies marine lab at Port
Royal on Thursday, February 2. - Andrew Smith/Photography Editor |
SYLLABUS
REQUIREMENTS - Explain
the formation of ionic and covalent bonds.
- Predict
the likelihood of an atom forming an ionic or covalent bond based on atomic structure.
- Write
formulae to represent ions and molecules.
- Explain
metallic bonding.
Now,
let us examine the following questions. 1.
Which solid does not contain covalent bonds? A.
Copper
B. Diamond
C. Graphite
D. Ice 2.
The elements X and Y form the compound X2Y. What is the correct electron arrangement
of the atoms X and Y?
| Atom
X | Atom
Y | | A.
2 : 7 | 2 |
| B.
2 : 2 | 2
: 7 | | C.
2 : 2 | 2
: 6 | | D.
2 : 1 | 2
: 6 | 3.
In which set do the three particles each have the same total number of electrons?
A.
Cl- Br- I-
B.
F- Ne Na+
C.
K+ Ca2+ Br-
D.
Li+ Na+ K+ 4.
What is the formula of iron (III) nitrate? A.
Fe (NO3)3
B.
Fe2 (NO3)3
C.
Fe2NO3
D.
Fe3 (NO3)2 5.
Elements X and Y react to form an ionic compound of formula XY. What could be
the proton (atomic) numbers of X and Y?
| | X | Y |
| A. | 3 | 8
| | B. | 6 | 8
| | C. | 8
| 16 |
| D. | 12 | 16 |
ANSWERS
AND COMMENTS
1. A. Covalent bonds are formed between non-metals. Diamond and graphite are made
up of carbon which is a non-metal, while ice (frozen H2O) consists of bonds between
hydrogen and oxygen which are also non-metals. This leaves copper which exhibits
metallic bonding.
2.
D. From the formula Y would form the ion Y2- and 2 X+ ions would combine to produce
X2Y. This means that Y is in Group 6 needing 2 electrons to be stable and X is
in group I since it has lost one electron to be stable. Thus the electron arrangement
for X is 2:1 and for Y is 2:6. 3.
B. Fluorine gains an electron to have the electron arrangement 2:8, the neon atom
is 2:8 and sodium loses an electron to have a 2:8 arrangement. This totals 10
electrons for all three particles. 4.
A. Iron (III) has a charge of +3 and the nitrate ion (NO3) - has a charge of -1.
These ions must combine in a way so that their charges cancel out to zero. Thus
it will take 3 nitrate ions (3 x -1) = -3 to cancel out the +3 charge on one iron.
-3 + 3 = 0. 5.
D. X has the arrangement 2:8:2 and Y has the arrangement 2:8:6. Thus as X loses
2 electrons to be stable, they are gained by Y which needs 2 to be stable. It
requires one X to bond with one Y. The formula is XY. It
is important to review the notes on this topic so that you can answer structured
and essay type questions as well. | 
