Day 14 – Covalent bonds
Sci 10 Chemistry
Covalent Bonds
Non-metal + non-metal
A compound without any metals?!???!
What happens when 2 nonmetals react?
Remember: Metals want to give away their electrons and nonmetals
want to accept them.
• A compound made of only nonmetals (Hydrogen counts as a
non-metal) is called a covalent or molecular compound.
Atoms in molecular compounds don’t want to lose their electrons
SO …
• electrons are shared amoung multiple atoms to have
full valence shells
Animation:
http://bcs.whfreeman.com/thelifewire/content/chp02/02020.html
H and Cl
Hydrogen and chlorine are both gases and nonmetals (even though
hydrogen is found in Group 1 (the alkali metals)).
Neither H nor Cl want to give up their electrons to form an ionic
sompound so they share them instead, forming a covalent bond
(which gives us a covalent compound)
H now has 2e- in its valence shell
and Cl has 8, so they are both full.
The line between H and Cl
indicates there are 2e- shared
between the 2 atoms.
This form is called a Lewis Dot
Diagram.
HOBrFINCl’s
The following elements exist in a diatomic form (2 atoms are always
bonded together). These diatomic molecules only exist in pairs of
atoms.
Draw Lewis Diagrams for H2, O2, Br2, F2, I2, N2 and Cl2
Triple bond
Double bond
Molecular compounds
Give the structural formula (Lewis diagram with
lines representing shared electrons) for the
molecular compound that will form from the
following pairs of elements:
1. bromine + iodine
2. nitrogen + chlorine
3. carbon + fluorine
4. sulfur + bromine
Answers
Structural formula
Br
Cl
I
N
Cl
F
F C F
F
Br S
Br
Cl
Practice
Draw Lewis structures for the following compounds:
H2O, CO2, NH3, SCl2, CH4, C2H6, P4, CBr4, CH2Cl2
P4 et S8: Elemental shapes (Chem 11)
• No need to memorize this but just to show you that
certain atoms bond to others forming specific angles.
The compounds that are formed with have specific
shapes.
Practice . . . again
Show the bond formation between each of the following pairs of
elements by drawing Lewis diagrams. Indicate if the compound
formed is ionic or covalent. Try to write the formula for the
compound.
a) K and Se
f) C and Cl
b) Br and Cl
g) C and O
c) Sr and Br
h) N and I
d) B and H
i)
Ca and N
e) Al and S
j)
Al and Br
Naming Covalent Compounds
1. Is it a covalent compound (non-metal +
non-metal)? If yes,
2. Name the element that is furthest left on
the periodic table first. Use a prefix if
there is more than one atom of this
element.
3. Name the second element. Use a prefix
to indicate the # of atoms (even if there is
only 1) and add the ending –ide.
Prefixes
# of atoms
Prefix
1
mono(only use when naming the 2nd element i.e. names of
covalent compounds never start with mono-…)
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
Examples and practice
• NO = nitrogen monoxide
• N2O = dinitrogen monoxide
• Name NO2
– nitrogen dioxide
• Name CO
– carbon monoxide
Try It!
Name the following molecular compounds:
1.
PI3
phosphorus triiodide
2.
SO2
sulfur dioxide
3.
SO3
sulfur trioxide
4.
S2F10
disulfur decafluoride
5.
CCl4
carbon tetrachloride
6.
N 2 O5
dinitrogen pentoxide
Name to formula
• Look at the prefixes to write the formula
• Ex: phosphorus pentachloride
• PCl5
Find the formula
• nitrogen tribromide
– NBr3
• nitrogen dioxide
– NO2
• sulfur pentoxide
– SO5
Naming diatomic molecules
• For the HOFBrINCl elements, they always exist
in pairs of atoms as gases
• To name them, just use the name of the
element
– H2 (g) = hydrogen
– O2 (g) = oxygen
– N2 (g) = nitrogen
To do
•
Day 14 Covalent Practice