Science 3200
Unit 1 Part 2
Bonding
Bonding of elements is the attraction
between atoms or ions
 Bonds that are formed between two nonmetals (i.e. elements found to the right of the
ladder on the periodic table) result in
molecular compounds
 Bonds that are formed between a metal and
a non-metal (i.e. one from the left and one
from the right of the ladder) result in ionic
compounds

Bonding
Ex. State whether each compound is
molecular or ionic.
a. NaCl
b. CO2
c. CF4
d. LiBr
Bonding

Some atoms will combine with other atoms
of the same element. These atoms are
found in nature like this. These are:
Hydrogen (H2)
 Nitrogen (N2)
 Oxygen (O2)
 Fluorine (F2)
 Chlorine (Cl2)

- Bromine (Br2)
- Iodine (I2)
- Astatine (At2)
- Phosphorus (P4)
- Sulfur (S8)
Bonding
Covalent Bonding (Molecular Compounds)
 Sharing of electrons
 the two non-metals both want to gain electrons
(to be like the noble gases), since both cannot
gain electrons at the same time they share.
 The unit formed by a covalent bond is called a
molecule (it is neutral; it has no charge)
Bonding
Ionic Bonding
 Gaining and losing electrons to form stable
compound
 The unit formed by an ionic compound is a
formula unit
 These form neutral compounds by the number of
electrons lost is equal to the number taken up
Compounds
Molecular Compounds
 Involve the sharing of electrons resulting in
covalent bonding
 Composed of two non-metals
 Exist as individual molecules
 May or may not be in lowest whole number
ratios
Naming Molecular
Compounds

Mono-atomic elements


Mono means one, so these are elements that exist on their
own in nature.
Namely the noble gases:






He – helium
Ne – neon
Ar – argon
Kr – krypton
Xe – xenon
Rn – radon
No need to memorize these as they
are listed in the periodic table
Naming Molecular
Compounds

Diatomic molecular compounds
These are non-metals that exist in nature as two
atoms joined together.
 They are:

– hydrogen
 O2 – oxygen
 N2 – nitrogen
 Cl2 – chlorine
 F2 – flourine
 Br2 – bromine
 I2 - iodine
 H2
Naming Molecular
Compounds

Polyatomic molecular elements
These are non-metals that exist in nature with many
atoms joined together
 These are:

– sulfur
 O3 – ozone
 P4 – phosphorus (red)
 S8
Naming Molecular
Compounds

Trivial names
These are names on compounds that do not
follow the guidelines put out by IUPAC.
 These are:

– water
 H2O2 – hydrogen peroxide
 NH3 – ammonia
 C12H22O11 – sucrose
 CH4 – methane
 CH3OH – methanol
 C2H5OH - ethanol
 H2O
Naming Molecular
Compounds

For binary molecular compounds, we use prefixes to
indicate the number of atoms that are present in the
compound. These are:






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Mono – one
Di – two
Tri – three
Tetra – four
Penta – five
Hexa – six
Hepta – seven
Octa – eight
Nona – nine
Deca - ten
Naming Molecular
Compounds
When writing the name of a molecular
compound start with the first element, not
changing the name, except for adding the prefix.
Then write the name of the second element with
the prefix and changing the ending of the name
to –ide.
 Note: the prefix mono on the first element only is
optional.

Naming Molecular
Compounds
For example, name the compound CCl4
The first element is carbon and there is only one
of them.
The second element is chlorine and there are 4 of
them. Therefore the name would be
monocarbon tetrachloride
or
carbon tetrachloride

Naming Molecular
Compounds
Ex 2. Write the name for P4F6.
Sol’n: The first element is phosphorus and there
are four atoms.
The second element is fluorine and there are six
atoms. Therefore the name of this compound is:
tetraphosphorus hexafluoride
Naming Molecular
Compounds
Your turn. Name each of the following.
1. P4F5
2. C2O4
3. NO3
4. Cl2O
5. N3Br2
6. O6I2
Writing Molecular
Formulas
When writing molecular formulas you look up
each element on the periodic table to determine
the chemical symbol for the element. (Don’t
forget that the ending on the second element has
been changed to –ide)
 Use the prefix on each element to determine the
number of atoms present. Write this number to
the right of the symbol and as a subscript.

Writing Molecular
Formulas
Ex. Write the formula for diboron hexahydride.
The first element is boron which is B and di
means 2.
The second element is hydride (or hydrogen)
which is H and hexa means 6.
 We have B2H6
Writing Molecular
Formulas
Ex. Write the formula for nitrogen triiodide.
The first element is nitrogen which is N and
since there is no prefix there is only one.
The second element is iodide (or iodine) and tri
means 3.
 We have N1I3 or NI3.
Writing Molecular
Formulas
Your turn. Write the formulas for each of the
following.
a. Carbon disulfide
b. Dinitrogen pentabromide
c. Silicon trifluoride
d. Hexaphosphorus pentachloride
Ionic Compounds
Ionic Compounds:
 Involve the transfer of electron(s), i.e gaining and
losing electrons, resulting in ionic bonding
 Made up of two oppositely charged ions (metal
and non-metal, or combination involving a
polyatomic ion)
 Are always written as empirical formulas (lowest
whole number ratio)
Naming Ionic Compounds

There are two categories of ionic compounds
that we will deal with.
1. Binary ionic
 Simple
ions (only single charges)
2. Polyatomic ions (complex ions)
Naming Ionic Compounds

Binary ionic compounds are composed of a metal
ion (+) and non-metal ion (-).

Binary simply means that only 2 ions are involved.
Ex. NaCl – the combination of a sodium ion and
a chloride ion.
Naming Ionic Compounds
Rules for naming simple binary ionic compounds
(meaning a compound with only two elements):
1. Name the metal (+) by writing the full name of
the metal.
2. Name the non-metal (-) by shortening the name
of the atom and adding the –ide ending.
Naming Ionic Compounds
Ex. NaCl  sodium chloride
CaF2  calcium fluoride
K2O  potassium oxide
**Note: Do NOT use prefixes – they are for
molecular compounds only (i.e. two non-metals)
Naming Ionic Compounds
Your turn. Name the following:
1. LiBr
2. AlCl3
3. Rb2S
4. Mg3P2
5. CaO
Writing Ionic Formulas
Rules for writing binary ionic formulas:
1. Write down the symbols of the ions involved.
2. Cross over the charges and write as subscripts.
3. Determine the lowest whole number ratio of
ions that will give a net charge of zero.
4. You do not need to write 1’s.
Writing Ionic Formulas
Ex. 1) Write the chemical formula for
potassium bromide.
2) Write the chemical formula for calcium
oxide.
3) Write the chemical formula for magnesium
iodide.
Writing Ionic Formulas
Your turn. Write the chemical formula for each
compound:
1. Sodium sulfide
2. Aluminum bromide
3. Barium iodide
4. Magnesium nitride
5. Aluminum nitride
Naming Compounds with
Polyatomic Ions
A polyatomic ion is two or more atoms
covalently bonded together that carry an overall
charge. Since they have a charge they can gain
or lose electrons to form ionic compounds.
 These ions are listed on your sheet but this list is
not exhausted, i.e. There are more polyatomic
ions than what’s listed.

Naming Compounds with
Polyatomic Ions
To identify these compounds look at the
elements involve. If you have more than two
elements in the compound and the compound is
not in your trivial names list than it contains a
polyatomic ion.
 You name these the same way you name ionic
compounds: look up the element/polyatomic ion
and write the names down changing the second
name to have the ending –ide.

Naming Compounds with
Polyatomic Ions
Ex 1. (NH4)3PO4
Ex 2. Cr(NO3)3
Naming Compounds with
Polyatomic Ions
Your turn. Write the name of the following
compounds.
1) Zn(OH)2
2) Pb(NO3)2
3) Mg(CH3COO)2
4) Na3BO3
5) K2Cr2O7
Writing Compounds with
Polyatomic Ions
When writing the formulas for compounds
containing a polyatomic ion(s), you treat the ion
as a single unit, not as individual elements.
 If you need to write a subscript for a polyatomic
ion, then you must enclose the ion in brackets.
 Remember to use the charges on the polyatomic
ions to determine how many you need to have a
balanced compound, NOT the subscripts!!!

Writing Compounds with
Polyatomic Ions
Ex 1. sodium chlorite
Ex 2. iron (III) sulfate
Ex 3. ammonium permanganate
Writing Compounds with
Polyatomic Ions
Your turn. Write the formula for each of the
following.
1. Sodium hydroxide
2. Potassium bicarbonate
3. Potassium carbonate
4. Magnesium hydroxide
5. Ammonium sulfate