The Structure of an Atom

1
The Structure of an Atom
2
Atoms

• All atoms are made up of protons, neutrons and
  electrons- these are subatomic particles
• Protons are positively charged particles found in
  the nucleus of an atom
• Neutrons are neutral particles also in the
  nucleus of an atom
• Electrons are negatively charged particles that
  orbit around the nucleus in an electron cloud
• These subatomic particles can be distinguished by
  mass, charge and location in an atom

3
Atomic Number and Mass Number

• Atomic Number- the number of protons in an
  element
• Atomic identifies an element
• Atoms of different elements have different atomic
  numbers
• Since elements are electrically neutral, the of
  protons equals the of electrons
• Mass Number- total number of protons and neutrons
  in an element
• p n0 mass number

4
Isotopes

• In Daltons atomic theory, all atoms of a given
  element are the same
• They have the same number of protons and
  electrons
• Atoms of the same element can have different
  number of neutrons these are called isotopes
• Same atomic number, different mass number

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Reading Information on Periodic Table
Atomic Number Symbol Name
6 C Carbon 12.011
Memorize Atomic of protons of protons
of electrons Atomic mass of protons of
neutrons
Average Atomic Mass
Why is the mass of carbon a decimal?
6
Practice
What is the atomic number of Li? How may
electrons are in Li? What is the mass number? How
many neutrons are in Li?
3 Li Lithium 6
Look at the periodic table in the back of you
book What is the name of an element that has 47
protons?
7
With your partner

• Pg 112 in your book
• 8 and 9
• Hand in