1. Molecule & Compound Notes

2. Most atoms are elements unless they are combined with other atoms.

3. Two or more atoms chemically joined together forms a molecule.

4. Molecules can be made up of the same type of atom (O2) or different types of atoms (H2O).

5. A substance made of two or more different types of atoms (elements) that are chemically bound together in a set ratio forms a compound.

6. Chemical bond
Force that holds the atoms of molecules & compounds together.

7. Properties of a compound are totally different than the properties of the individual elements that make it up. + =
carbon
oxygen
carbon dioxide

8. Chemical formula
Uses element symbols & subscripts to show the ratio of elements in a compound.

9. A substance made of two or more different types of atoms (elements) that are chemically bound together in a set ratio forms a compound.

10. Salt=>
(1 sodium, 1 chlorine)
NaCl

11. Carbon dioxide=>
(1 carbon, 2 oxygen)
CO2

12. (6 carbon, 12 hydrogen, 6 oxygen)
Glucose=>
(6 carbon, 12 hydrogen, 6 oxygen)
C6H12O6

13. Chemical reaction
Occurs when bonds are formed or broken=> requires or gives off energy.

14. Chemical equation
Short, simple way to describe a chemical reactions using symbols & formulas instead of words.

15. Identifies the elements that make up the compound.
Symbol
Identifies the elements that make up the compound.
Fe HCl FeCl H 2
chlorine
iron
hydrogen

16. Number of atoms of that element in one molecule.
Subscript
Number of atoms of that element in one molecule.
Fe HCl FeCl H 2
2 chlorine atoms
2 hydrogen atoms

17. Number of each molecule in a reaction.
Coefficient
Number of each molecule in a reaction.
Fe HCl FeCl H2
2 molecules of HCl

18. Shows the directions of the reaction.
Yield sign
Shows the directions of the reaction.
Fe HCl FeCl H 2

19. Counting Atoms H2O 3 4H3PO4 32 Al2O3 5 3Na2SO3 18 Compound # of atoms
# of elements & their names
# of molecules
H2O 3
2-hydrogen & oxygen 1
4H3PO4 32
3-hydrogen, phosphorus & oxygen 4
Al2O3 5
2-aluminum & oxygen
3Na2SO3 18
3-sodium, sulfur & oxygen

20. Reactants
The substances you begin with in a chemical reaction (left side of the yield sign).

21. Products
The substances you end with in a chemical reaction (right side of the yield sign).

22. Basic Rules for Balanced Equations

23. Every chemical compound has a formula that CANNOT be altered!

24. NEVER change a formula when balancing equations!!

25. Law of conservation of mass:
During a chemical reaction, atoms cannot be created or destroyed…

26. So the number of atoms at the beginning of a reaction MUST match the number at the end of the reaction!

27. Coefficients can be added before an element or molecule.

28. Subscripts are always found after an element or molecule & cannot be changed without changing the substance!

29. How can you tell that the following equation is not balanced?

30. C3H8 + O2 => CO2 + H2O

31. For fun… let’s see if you can balance it!
(HINT: remember that you must have the same number of each atom on both sides!)

32. C3H8 + 5O2 => 3CO2 + 4H2O