3.4 – Atoms Notes
The Atom
• The atom consists of 3 particles called ___________, ____________, and _____________.
o Proton – located ____________ the nucleus and has a ________________ charge
o Neutron – located _____________ the nucleus and has a _______________ charge
o Electron – located _____________ the nucleus and has a ______________ charge
• Although there are 3 parts to the atom, the proton and neutron account for basically all of the
mass of the atom. The electrons contribute very little overall mass to the atom.
• Atomic Number – number of ________________ of each atom of that element.
o this is what identifies the elements!
• Atomic Mass – the total number of ____________ and _____________ that make up the nucleus
of the atom.
• Isotope – atoms of the same element that have different atomic _____________.
Example:
Isotope Protons (atomic #) Neutrons Atomic Mass
Protium 1 0 1
Deuterium 1 1 2
Tritium 1 2 3
• This means that isotopes of the same elements have the same number of _______________,
but a different number of __________________.
Designating Isotopes
• There are 2 ways to write isotopes: Hyphen Notation and Nuclear Symbol
1) Hyphen Notation: Carbon – 12
-write out the element name in full, and then write out the atomic mass after the hyphen
2) Nuclear Symbol: 126C
-write out the element symbol, the superscript is the atomic mass and the subscript is the
atomic number
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