1. TEKS 8.5D recognize that chemical formulas are used to identify substances and
determine the number of atoms of each element in chemical formulas containing
subscripts
TEKS 8.5F recognize whether a chemical equation containing coefficients is balanced
or not and how that relates to the law of conservation of mass
Chemical
Formula
Notes

2. Atoms are the basic
units of matter.
Atoms join together
chemically to form
elements.

3. Elements are pure
substances made of
only one kind of atom.

4. Elements are
represented
by 1-2 letters
called symbols
on the Periodic
Table.

5. Molecule is a term
used to refer to 2
or more atoms
which are bonded.
Examples are O2
and CO2.

6. CO2 is both a
molecule and a
compound as well.

7. Compounds are
substances made of two
or more different
elements chemically
combined in a set ratio.

8. A chemical
bond, or electric
force, holds the
atoms together
in a compound.

9. The properties of a
compound are totally
different from the
elements that make up the
compound.
+
carbon
=
oxygen
carbon dioxide

10. For example, salt is composed
of sodium (Na); a silvery metal;
and chlorine (Cl); a stinky,
green gas.

11. When the two elements bond to
form NaCl, they form solid
white crystals which you can
eat!
Salt=>
(1 sodium, 1
chlorine)

12. Chemical formula
Chemical formulas
are used to show
the ratio of
elements in a
compound. The
elements present in
a compound are
identified with the
element’s symbol.

13. If more than 1 atom of
an element is in the
compound, it is shown
with a subscript.
O2

14. For example, water; H2O;
has 2 atoms of hydrogen.
Since oxygen has no
subscript, there is only 1
atom of oxygen

15. Sometimes,
substances contain
more than 1 molecule
of an individual
compound.

16. This is shown with a
coefficient.
Coefficients are written
in front of the
compound’s formula.
4 H2

17. For example, 2SO3 means
there are 2 molecules of
sulfur oxide. The total
number of the atoms in 2SO3
would be 8; 2 atoms of sulfur
and 6 atoms of oxygen.

18. Compound
Name
Elements present
Total # of atoms
# of molecules
H2O
water
2-hydrogen
1-oxygen
3
1
ZnCO3
zinc carbonate
1-zinc
1-carbon
3-oxygen
5
1
Al2O3
aluminum
oxide
2-aluminum
3-oxygen
5
1
18
3
24
1
6-sodium
3-sulfur
9-oxygen
6-carbon
12-hydrogen
6-oxygen
3Na2SO3
sodium sulfate
C6H12O6
glucose
CH4
methane
1-carbon
4-hydrogen
5
1
2HCl
hydrochloric
acid
2-hydrogen
2-chlorine
4
2