3 Oct 2016
Objectives:
Neutron to Proton ratio and
nuclear stability
1.
1.
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Write in space on
back sheet.
The masses of protons, neutrons and
electrons in g are very small and difficult
to work with.
Chemists developed a method of
measuring the mass of an atom relative to
the mass of a specifically chosen atomic
standard.
…atomic standard
Carbon-12 atom
One carbon-12 atom was assigned a mass
of exactly 12 atomic mass units (amu).
One atomic mass unit (amu) is defined as
th
1/12 (one twelfth) of the mass of a
carbon-12 atom.
1 amu is close to the mass of a single
proton or single neutron.
See p 102 Table 4-2
Add to your “Periodic Table of The Elements”
Add to your “Periodic Table of The Elements”
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All atoms are neutral
have no net charge
Number of protons (+) = number of electrons (-)
np + (ne-) = 0
Problem
Solving
Using average atomic mass to
identify an element
53
Problem
Solving
Using average atomic mass to
identify an element
53
Problem
Solving
Using average atomic mass to
identify
Details an element
53
Problem
Solving
Using average atomic mass to
identify
Details an element
Isotopes and Atomic Structure
Complete the table - what patterns do you notice?
Isotopes and Atomic Structure
Complete the table - what patterns do you notice?
Isotopes and Atomic Structure
Complete the table - what patterns do you notice?
Isotopes and Atomic Structure
Complete the table - what patterns do you notice?
The Band of Stability
Ratio gradually
increases to maximum
of 1.5: 1 for largest
atoms
For atoms with low
atomic number
(<20) 1:1 n/p ratio
page 811 textbook
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