Download ISOSTOPE NOTES - Mr. Collier`s 9th Grade Physical Science

Notes on Isotopes
• Remember Protons are (+) and
Electrons are (-).
• Neutrons were the last subatomic particles to be discovered
because they have no electrical
charge.
• All atoms of an element have the same
number of protons. (Atomic #)
• Neutral atoms have equal protons and
electrons
• The number of neutrons can vary from
one atom of an element to another.
–These variations are called
ISOTOPES.
• Isotopes are atoms of the same element
that have different masses because they
have different numbers of neutrons.
–Subatomic particles are so small that we
don’t use grams, we use AMU (atomic
mass units)
–Protons and Neutrons have about the
same mass: 1AMU.
–Electrons have so little mass they don’t
affect the atom’s mass.
• Mass number tells us how
many protons and neutrons
are in the nucleus of an atom.
–It is always a whole number.
Isotope Notation
• 2 Forms:
Carbon-12 (12 is the mass number)
• Carbon will always have 6 protons
How many neutrons does Carbon-14 have?
there are 14 total protons and neutrons.
6 of them are protons.
So 14 (total) – 6 (protons) = 8 Neutrons
How many neutrons does Carbon-13 have?
• Mass Number is specific to an isotope.
– Not written on periodic table
– Rounding the atomic mass usually gives you
the most common mass number, but not
always.
• Atomic Mass (atomic weight) is the
weighted average mass of all of the known
stable isotopes of an element.
– Most have decimals because they are
averages.
– This is the # on the periodic table