Atom Notes

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Atom Notes
Adapted from Harris Middle School NEISD
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An atom is the basic unit of all matter. It is
the smallest particle into which an element
cannot be broken down into a simpler substance.

• There are 2 main locations in an atom
• atomic nucleus (the center with most of the
  mass of the atom)
• electron cloud (surrounds the nucleus)
• There are 3 subatomic particles in an atom
• subatomic means smaller (than the atom itself)
• 3 particles protons, neutrons and electrons
• the numbers of these particles make atoms
• different from one another.

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Name of subatomic particle Charge of Particle Where it is found Size/mass
proton Positive () inside the nucleus- identifies the atom 1 atomic mass unit
electron Negative (-) in electron cloud / orbiting around nucleus- determines reactivity of element Almost zero 1/1836 amu (very small!)
neutron Neutral (0) inside the nucleus- just adds mass/weight 1 atomic mass unit
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periodic table chart where all elements are
arranged by atomic number and properties-this is
your cheat sheet to make models of atoms!!

• the atomic of protons elements identity
• of electrons of protons in an atom
  (neutral)
• Symbol is 1 or 2 letters- First letter is always
  capitalized if it has 2 letters the second is
  lower case
• the atomic mass of protons of neutrons
• of neutrons atomic mass atomic
• atoms of an element can have different numbers of
  neutrons (these atoms are isotopes)

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Label the subatomic particles in the picture
p proton n0 neutron e- electron
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Color the protons blue
Color the neutrons red
Color the electrons green