Diatomics
In nature, some atoms don’t exist as individuals. They may “latch onto” one or more
other particles of the same kind. The ones that bond with only one more are called the
diatomic elements, or diatomics.
ex.
A fluorine atom will pair with a second fluorine atom to make an F2 molecule.
Draw the shell diagram
for this diatomic in the
box on the right.
To remember which elements are diatomic, think of Count “HOFBrINCl”.
ex.
Draw the shell diagrams for O2 and N2 below.
Substance
Representative Particle
Examples
elements
atoms
K, Li, Al, Ne, etc.
diatomic elements
molecules
H2, O2, F2, Br2, I2, N2, Cl2
ionic compounds
formula units
NaCl, BaO, Al(OH)3, etc.
molecular compounds
molecule
H2O, SF3, Br2Cl3
The Law of Conservation of Mass – Balancing Equations
def’ns:
In a chemical reaction, the substance(s) that you start with are
called reactant(s). They are located on the left side of the equation.
The substance(s) that you end up with are called the product(s).
They are located on the right side of the equation.
ex.
When sodium is added to oxygen, we get sodium oxide.
Na(s)
+
O2(g)

Na2O(s)
reactants
product
The Law of Conservation of Mass states that in a chemical reaction, matter is
neither created nor destroyed. Thus, in a chemical equation, there must be the
same amount of individual atoms on both sides. The process used to make
sure that this is the case is called balancing equations.
exs. Balance the following chemical equations.
(1)
Na +
O2 
Na2O
(2)
K
+
Cl2 
KCl
(3)
Al
+
Br2 
AlBr3
Assignment – Balancing Equations #1
Directions:
Balance the following equations. Show any and all work below the equation. The last
one is an example of a type of question you would see in a grade 11 chemistry class.
(1)
Li
+
S

Li2S
(2)
Mg
+
N2

Mg3N2
(3)
Na
+
H2O 
NaOH
(4)
Al2O3
(5)
P4
+
O2

P4O10
(6)
FeS2 +
O2

Fe2O3
(7)

Al
+
+
H2
+
SO2
O2
barium chloride + magnesium sulfate  barium sulfate + magnesium chloride