Transcript Atomic Structure + Isotopes

The Atom
Quick!
Time yourself
writing the
numbers from
1000-1050.
Then, multiply
the time by
20,000
How small is an atom?
A human hair is about 1 million atoms across
And… a million is a lot! It would take you at least 20 days without
sleeping (at just over 1-second per number) to count to 1,000,000 out
loud.
50 million (all the people in Oregon x 12.5 or almost twice the number of people in California)
atoms lined up = 1 cm. In other words, if all of the people in Oregon were
atoms & they lined up holding hands, the line would be less than 1mm
long
If each atom in a single marble were the same size as a grain of sand,
you would end up with enough sand to cover the whole of Oregon with a
layer close to a thousand feet (2/3 or a mile) thick.
If you walked around the equator of the earth continually without
stopping to sleep or eat, it would take about 12,500 hours or 520 days.
It's a big place!
If a golf ball could be magnified to the size of the whole earth, most
of its atoms would be more or less the size of a golf ball
Atomic Structure
Parts of an Atom

Proton
• +1 charge
• In nucleus
only
• Mass= 1amu
(1.6 x 10-24g)

Neutron
• 0 charge
• In nucleus

Electron
• -1 charge
• Around
only
• Mass=
1amu (1.6 x
10-24g)
•
nucleus- in
shells
Mass= 9.1 x
10-34g
(relatively
insignificant)
Electrons

But… Electrons take up by far
the most space, 10,000 times
more than the nucleus

Nucleus = basketball then
electrons stretch out in a
diameter of 7.5km (all the way to
Phil’s Trails, Target, Elk
Meadow School- almost)

Nucleus= marble then electrons
stretch 100m (size of a football
field)
Atomic Structure

Atomic Number = # of protons and #
of electrons

Mass number = # of protons +
neutrons
Try these…


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
I have an atomic number of 13
• Aluminum
I have an atomic mass of 32
• Sulfur
I have 83 electrons
• Bismuth
Number of neutrons in Cobalt (Co)
• 32
Have 10 neutrons
• Neon AND Fluorine
But wait!

How many neutrons does Chlorine
have?
18.5?

Isotopes= atoms with the same # of
protons, but different # of neutrons (and
thus different mass)
• Ex: sodium-23, sodium-24
• Symbol:
Mass
Radioisotopes

Unstable isotopes= radioactive=
radioisotopes
• Carbon-14 decays into carbon-12 over time
by kicking off neutrons (or parts of neutrons)

Have many uses!
• Americium-241= smoke detectors
• Technetium-99= thickness gauges
Back to Chlorine….

Atomic Mass on the periodic table is a
weighted average of the atomic masses
of all isotopes (see p.119)

Average Atomic Mass = (% of isotope 1)(mass of
isotope 1) + (%of isotope 2)(mass of isotope 2)
+…

Chlorine = 75.77%(35) + 24.33%(37) = 35.5 amu
So…

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What is the most common isotope of
Hydrogen? Hydrogen-1
How about Zinc? Zinc-65
Nope
Is this the most common Li isotope?
Carbon is 98.89% carbon-12 and 1.11%
carbon-13. What’s the average atomic
mass?
98.89%(12) + 1.11%(13) = 12.011 amu
A couple more…


What’s the most common isotope of
Gallium-70
gallium?
If element X is 57% X-25, 29% X-26 and
14% X-27, what’s the average atomic
mass of X?
57%(25) + 29%(26) + 14%(27) = 25.57 amu