1. Chapter 2 The Material World
Molecules
Chapter 2
The Material World

2. Review – Counting Atoms

3. Counting Atoms
When counting atoms in a molecule you must look at:
The number of elements present
Remember: focus on the upper case letters
The subscripts
Element
Element
Ca3(PO4)2
Element
Subscript
Subscript
Subscript

4. How many atoms are in the following molecule?
HCl 2

5. How many atoms are in the following molecule?
H2SO4 7

6. How many atoms are in the following molecule?
Ca(OH)2
Remember: subscripts on the outside of the brackets apply to everything inside (distribute) 5

7. Representations of the Atom

9. Bohr-Rutherford Model
Draw the Bohr-Rutherford model for Chlorine Cl
17p+
18n0

10. Simplified Atomic Model
Draw the simplified atomic model of Chlorine Cl
17p+
18n0
2e-
8e-
7e-

11. Lewis Dot Model
Draw the Lewis dot model of Chlorine Cl

12. What is a molecule ?
A group of atoms connected to one another by a chemical bond.
Variety of molecules is virtually limitless
How atoms combine to form molecules is determined by:
The number of valence electrons (electrons in the outermost shell)
The type of atom (metal, non-metal or metalloid)

13. Particle Model
Draw the particle model for water
Dalton!
H2O

14. We’ll get back to bonds later
Ball and Stick Model
Bond!
H2O
We’ll get back to bonds later