Chemistry.notebook
Quiz # 3
1.
Particle
April 16, 2012
Charge
Location
Nucleus
2.
3. Which of the following element(s) above are very stable?
Chemistry.notebook
April 16, 2012
Curricular Outcome of the Day
Counting Atoms
What elements & how many atoms
of each element is found in a
chemical formula? (307-16)
Scrapbook due Wednesday (10)
Rules for Counting Atoms
1. The symbol of an element represents one atom of
that element.
Example: Na – 1 atom of Sodium
2. The subscript number indicates the number of
atoms for that element.
Examples: H2 – 2 atoms of Hydrogen
H2SO4 – 2 atoms of Hydrogen
H
1 atom of Sulfur
4 atoms of Oxygen
O
O
O
Na
O
H
Chemistry.notebook
April 16, 2012
3. A subscript outside a bracket multiplies
by all the elements inside the brackets.
Examples: Mg3(PO4)2 – 3 atoms of Magnesium
1×2 = 2 atoms of Phosphorous
4×2 = 8 atoms of Oxygen
Al2(SO4)3 - 2 atoms of Aluminum
1×3 = 3 atoms of Sulfur
4×3 = 12 atoms of Oxygen
Mg
Ca
4. A coefficient is a number written in front of a chemical
formula. The coefficient indicates the number of molecules of
that compound. A coefficient multiplies the number of atoms
of each element in the formula.
Examples:
2H2O = H2O + H2O = 4 atoms of H & 2 atoms of O
3CuSO4 = CuSO4 + CuSO4 + CuSO4 = 3 atoms of Cu
3 atoms of S
12 atoms of O
4Pb(NO3)2 = Pb(NO3)2 + Pb(NO3)2 + Pb(NO3)2 + Pb(NO3)2
= 4 atoms of Pb
1×2×4 = 8 atoms of N
3×2×4 = 24 atoms of O
Chemistry.notebook
Examples:
H2O
CaCl2
2NaOH
2Mg(CH3COO)2
April 16, 2012
Chemistry.notebook
April 16, 2012
Try these:
A) MgCl
2
Na2CO3
K2CrO4
B) 4Mg(OH)
2
C) 4Al (SO )
2
33
Ca3(PO4)2
3 BaCl2