WORKSHEET ON CHEMICAL BONDING
COVALENT BONDING
Covalent bonding involves the sharing of electron pairs between two atoms. This is most
often between non-metal atoms (but there are a number of compounds between metals and
non-metals that are covalent). A single covalent bond involves one shared pair of electrons.
In many compounds, atoms will share electrons to enable their valence shell to become like
the nearest Noble Gas. This is normally 8 electrons (the “Octet Rule”), apart from Hydrogen.
Draw “dot and cross” diagrams (outer electrons only) to show the bonding in the following
covalent molecules:a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
Hydrogen fluoride – HF
Chlorine – Cl2
Oxygen – O2
Nitrogen – N2
Silicon tetrachloride – SiCl4
Ammonia – NH3
Carbon dioxide – CO2
Hydrogen cyanide – HCN
Ethane – C2H6
Ethene – C2H4
DATIVE (CO-ORDINATE) COVALENT BONDING
You have seen in question 3 that some molecules have atoms which are electron deficient.
Positive ions also have “missing” electrons. You have also seen that some molecules have
non-bonding pairs of electrons (lone pairs). These molecules can donate their lone pair of
electrons into the empty orbital of an atom or ion. An extra covalent bond can then be
formed.
2) Draw “dot and cross” diagrams (outer electrons only) to show the bonding in the
following covalent molecules or ions which contain dative bonds. Indicate the dative
bonds clearly on your diagrams.
The ammonium ion – NH4+
The hydroxonium ion – H3O+
The compound formed between BF3 and NH3
Once a dative covalent bond has been formed, is there any difference between this and an
“ordinary” covalent bond?
e) Does making a dative bond using the lone pair of electrons on the N atom in ammonia
break the “octet rule” for the N atom? Explain.
a)
b)
c)
d)
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