Selected topics Chapter 8 – Earth Chemistry

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Transcript Selected topics Chapter 8 – Earth Chemistry

Selected topics
Chapter 8 – Earth Chemistry
• All matter made of ATOMS
• Elements are substances with one kind
of atom.
• There are 92 naturally-occurring
elements.
• Listed in Periodic Table.
Nearly 99% of earth’s crust
made of just 8 elements:
Notice anything
about these
elements?
Where are they
in the periodic
table?
Why?
Notice that OXYGEN (O) AND SILICON (Si)
make up about 75% of the crust.
We will see that most minerals are
“silicate minerals”, containing Si and O.
These minerals make up the rocks of the crust.
Granite – composed of
several silicate minerals.
ATOMS
Example:Carbon
Atomic# 6
Mass# 12
Nucleus – 6 protons,6 neutrons
Outside nucleus – 6 electrons
ISOTOPES
Atoms of same element, but with
different number of NEUTRONS, so
different mass number.
carbon-12
carbon-14
nucleus
6 protons
6 neutrons
6 electrons (not shown)
6 protons
8 neutrons
6 electrons (not shown)
We talk about isotopes because they
are important in “dating” rocks and
other materials (finding out how
old they are). More on this later.
Carbon-14 decaying and
turning into nitrogen-14.
The ratio of carbon-12 to
carbon-14 can be used
to tell how old something is.