Atoms and Compounds
ICS III
Week 4
How to read the Periodic Table
All Atoms Have Mass

Mass number
 The
total number of protons and
neutrons in an element


Each proton and neutron have an
average mass of about 1 amu (atomic
mass unit)
 6 protons and 6 neutrons
 12.01 or 12
Atomic Mass Unit
 A weighted
average mass of the
atoms in a naturally occurring
sample
Practice with mass numbers

What is the mass number for Sodium?


What is the mass number for Oxygen?


22.99 or 23
16.00 or 16
What is the mass number for Hydrogen?

1.01 or 1
Elements vs. Compounds

Element
Simplest form of matter.
 Can not be broken down


Compound

Substance that contains two or more
elements chemically combined in a fixed
proportion
Element vs. Compound
O
 The element oxygen
 O2
 The compound dioxide (two oxygen)


Contains 2 oxygen elements bonded together
Element vs. Compound

2 Hydrogen elements (H) + 1 Oxygen (O) element


H 2O
1 Carbon elements (C) + 2 Oxygen (O) element

CO2
How to find the molecular mass of
a compound
Molecular Mass
 Molecular Weight

 All
matter has
mass, or weight
 The sum of the
atomic masses of
the atoms of each
element
•What is the molecular weight of CO2?
How to find the atomic mass of a
compound
CO2
 1 Carbon atom



1 x 12 = 12
2 Oxygen atoms

2 x 16 = 32
CO2
 12 + 32 = 44

How to find the atomic mass of a
compound

Find the atomic mass of H2O.


Find the atomic mass of NaCl.


18
58
Find the atomic mass of C6H12O6.

180
Mass of compounds
16
17
18
36
2
Amount vs. Weight
Substance amount
units
weight
Apples
1 dozen
12
555 grams
Donuts
1 dozen
12
250 grams
Feathers
1 dozen
12
5 grams
Bricks
1 dozen
12
10,000 g
•What do all these substances have in common??
•Amount…… 1 dozen or 12 units
•Conversion factor?????????
•What is different about all these substances???
•The weight….
Mole
The number of atoms in 12 grams of
carbon-12.
 The atomic mass of an element is the
weighted average of the mass of one mole
of its atoms
 1 mole of a compound = atomic mass of
the compound
 (Molar Mass)…


Mole Mass… Mass of one mole of compound
What is a mole?
The term mole is used to talk
about mass. One mole of a
substance is its relative atomic mass,
or relative formula mass, in grams.
For example, the relative
atomic mass of carbon is 12,
so one mole of carbon
atoms weighs 12 grams.
What is the mass of one mole of hydrogen atoms?
Molar Mass

The atomic mass of an element or
compound expressed in grams per mole
Atomic mass goes here
CONVERSION FACTOR
Moles and Mass

1 mole of ______ has a molar mass of . . . . . .
16 g/mol

17 g/mol
18 g/mol
36.5 g/mol
2 g/mol
2 grams of Hydrogen gas (H2) = 1 mole of Hydrogen gas (H2)
What is the mass of one mole?
Moles

Beaker of Water
Mass of water is 18 g
 How many moles??

1
mole
 1 mole H2O = 18 g
Moles

Beaker of HCl
Mass of HCl is 36 g
 How many moles??

1
mole
 1 mole HCl = 36 g
1 mole
1 mole
18 g
36 g
Amount vs. Weight
Substance amount
units
weight
Apples
1 dozen
12
555 grams
Donuts
1 dozen
12
250 grams
Feathers
1 dozen
12
5 grams
Bricks
1 dozen
12
10,000 g
•What do all these substances have in common??
•Amount…… 1 dozen or 12 units
•Conversion factor?????????
•What is different about all these substances???
•The weight….
Moles

Beaker of Water
Mass of water is 36 g
 How many moles??

2
moles
CST Questions

How many moles of carbon -12 are
contained exactly 6 grams of carbon -12
1.
2.
3.
4.
0.5 moles
2.0 moles
3.0 moles
16.0 moles
1. What is the Molecular mass?
12 g/mole
2. Convert grams into moles
6gC
1 mole CH4
x ----------------12 g CH4
CST Questions

How many moles of CH4 are contained in
96.0 grams of CH4?
1.
2.
3.
4.
3.00 moles
6.00 moles
12.0 moles
16.0 moles
1. What is the Molecular mass?
16 g/mole
2. Convert grams into moles
96.0 g CH4
1 mole CH4
x ----------------16 g CH4
How many moles?