1. The molecular formula tells us how many atoms are in a compound.
In this molecule are 2 atoms of hydrogen (H) and one atom of oxygen (O)
We write this as H2O
this number has to be small

2. a number here means 2 molecules of water
Common mistakes H O
2H2O
a number here means 2 molecules of water H O

3. a number here means 2 atoms of oxygen - a different compound
Common mistakes H O
HO2 O
a number here means 2 atoms of oxygen - a different compound

4. Common mistakes H
H2O2 O H O
This would also be a different chemical, because it would have two oxygen atoms and two hydrogen atoms.

5. Molecular formula KEY hydrogen atoms H2 oxygen atoms H2O carbon atoms
CO2 O C N
nitrogen atoms H N
NH3 H C
CH4

6. Can you give the Molecular formula?
KEY
hydrogen atoms H O O O
oxygen atoms C
carbon atoms C O N
nitrogen atoms N N H C H C H

7. Step 1 - identify the atoms
Naming compounds
Step 1 - identify the atoms H O

8. Step 1 - identify the atoms
Naming compounds
Step 1 - identify the atoms H O
H = hydrogen
a compound with hydrogen
is hydrous or a hydride
O = oxygen
a compound with oxygen
is an oxide

9. Naming compounds Step 2 - count the atoms 1 oxygen atom
2 hydrogen atoms
2 atoms is called di-

10. Step 3 - put it all together
Naming compounds
Step 3 - put it all together H O
di hydrous oxide
means 2 hydrogen atoms
& 1 oxygen atom
the common name for this compound is water

11. (tri-hydrous nitride)
NAME THE COMPOUND
KEY
hydrogen gas
(element)
hydrogen atoms H H O H O
water
(di-hydrous oxide)
oxygen atoms C
carbon atoms
carbon dioxide O C N
nitrogen atoms
ammonia
(tri-hydrous nitride) H N
Remember
mon - 1
di - 2
tri - 3 H C
methane

12. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)

13. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)

14. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)

15. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)

16. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)

17. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)

18. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)
2. Draw the particle diagrams H

19. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)
2. Draw the particle diagrams O H

20. hydrogen(g) + oxygen(g) —> water(g)
Combustion Equations
1. Word equation with state symbols
hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
H2(g) + O2(g) —> H2O(g)
2. Draw the particle diagrams H O O
H2(g) O2(g) —> H2O(g) H

21. hydrogen(g) + oxygen(g) —> water(g)
2. Replace words with symbols
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O O
H2(g) O2(g) —> H2O(g) H

22. But the reactants have 2 oxygen atoms The products have 1 oxygen atom
2. Replace words with symbols
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O O
H2(g) O2(g) —> H2O(g) H
But the reactants have 2 oxygen atoms
The products have 1 oxygen atom

23. Now the oxygens balance We multiply this molecule by 2
2. Replace words with symbols
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O H O O
H2(g) O2(g) —> H2O(g) H
Now the oxygens balance
We multiply this molecule by 2

24. But the hydrogens do not
2. Replace words with symbols
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O H O O
H2(g) O2(g) —> H2O(g) H H
We need more hydrogen atoms on this side so we add another hydrogen molecule
But the hydrogens do not

25. NOW we have the same atoms on both side of the equation
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O H O O
H2(g) O2(g) —> H2O(g) H H
5. Balance the symbol equationn to match
NOW we have the same atoms on both side of the equation

26. hydrogen(g) + oxygen(g) —> water(g)
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
2H2(g) + O2(g) —> H2O(g)
4. Balance the particle diagram first H O H O O
H2(g) O2(g) —> H2O(g) H H
5. Balance the symbol equationn to match

27. hydrogen(g) + oxygen(g) —> water(g)
2. Draw the particle diagrams
Combustion Equations
hydrogen(g) + oxygen(g) —> water(g)
2H2(g) + O2(g) —> 2H2O(g)
remember a number here means 2 molecules of water
4. Balance the particle diagram first H O H O O
H2(g) O2(g) —> H2O(g) H H
5. Balance the symbol equationn to match