Download Chapter 5 Isotopes

Chapter 3
Isotopes
Part II
Atoms
Nucleus is center
core.
 Nucleus is made
of Protons &
Neutrons.
 Electrons orbit the
nucleus.

Atomic Number


The Atomic Number
is the number of
protons found in the
nucleus.
All atoms of an
element have the
same Atomic
Number
Mass Number
Mass number is the number of neutrons
and protons in the nucleus.
 This number is not always the same for all
atoms in an element.

Isotopes
Isotopes


Isotopes of an
element have the
same number of
protons but different
numbers of
neutrons.
The charge is the
same, but they have
a different mass.
But how it that different from Atomic
Mass?
Atomic mass takes
into account the
relative abundance
of each isotope.
 The weight of
atoms are
measured in amu’s

What is an amu?


Amu is Atomic Mass
Unit.
It is defined as 1/12th
of the mass of a
Carbon-12 atom.
Relative abundance
 Most
elements have one isotope that
is the majority share of the element.
Calculating the Atomic Mass from
the sum of the isotopes.
The atomic mass takes the natural
abundance into consideration.
 Assume the sample is 1 gram.
 99.985% of 1.007825035 is 1.007673861
 0.015% of 2.014101779 is 3.02115 x10-4
 The sum of these is the atomic mass:
 1.007975976 amu

Worksheet