Ions and Isotopes
Ions
-
atoms that have lost or gained electrons
-
example: calcium atoms tend to lose
2 electrons in reactions
calcium starts with 20 protons and 20 electrons so that by losing 2
electrons it now is
an ion and is written as Ca2+ (it has 2 more protons than
electrons)
-
example: oxygen tends to gain
2 electrons in reactions
oxygen starts with 8 protons and 8 electrons and when it gains those 2
electrons it
becomes an ion that is written as: O2- (2
more electrons than protons)
Isotopes
-
these are atoms of the same element that have different
numbers of neutrons in the nucleus
-
their mass numbers will be different but atomic number is
the same
-
example: boron has an atomic mass of 10.81
which is an average of boron-11 that exist in
nature 80% of the time and boron-10 that only exist in 20% of the cases.
-
Hydrogen has 3 forms: natural hydrogen with 1 proton
and 1 electron, deuterium with 1 proton, 1 neutron, and 1 electron, and
tritium with 1 proton, 2 neutrons, and 1 electron.
Bromine-79 and bromine-81 has atomic mass (M) of 79.904
there is no bromine 80
Boron-11 (80 % abundant) and boron -10
(20 % abundant) has M = 10.81 (abundance shifts average mass)
Cobalt-60 and gold-181 are used in cancer research, both are man-made
Carbon-13 and oxygen-18 used to find pathways of photosynthesis
Rubidium-87 used in archeological dating
