Download BellWork 2/16/2015

Mg2+
ClFe2+
O2These elements are written to describe what? Grab
a textbook and look it up if needed.
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Isotopes are atoms that have a different
number of neutrons.
An atom is still the same element if it has
different neutrons - it’s just a different
version!
Neutrons can be added to an atom without
altering the number of protons and electrons
it has.
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For example, the element carbon has 13
different isotopes!
You are familiar with C-12 (the C stands for
carbon, and the 12 is it’s atomic mass)
◦ This isotope has 6 neutrons
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C-14 (atomic mass 14) is used for carbon
dating and has 8 neutrons!
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In an isotope, the number of protons and
electrons never changes- only the number of
neutrons is different
This means that each isotope of a particular
element has a different atomic mass than
another isotope of the same element
◦ Remember: C-12 has an atomic mass of 12 and C14 has an atomic mass of 14!
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There are several different ways to write
symbols for isotopes, each of which is
perfectly legitimate.
The other ways to write
each of these hydrogen
isotopes from top to
bottom are:
Hydrogen-1 or H-1
Hydrogen-2 or H-2
Hydrogen-3 or H-3
Example
Write down the three different notations for a carbon atom with 6
protons and 6 neutrons.
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1)
2)
3)
4)
5)
Calculate the number of neutrons there are
in the following isotopes (use your periodic
table to find the atomic numbers)
Carbon-14
Nitrogen-15
Sulfur-35
Calcium-45
Iodine-131