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MODELS OF THE ATOM
SCIENCE 9
ALL ATOMS ARE NOT CREATED
EQUAL
• Atoms can vary from one to the next of the same
element in the number of neutrons they have in their
structure
• Two atoms that have the same number of protons but
different number of neutrons are called isotopes
• Carbon has three isotopes:
• carbon-12
• 6 protons, 6 neutrons, 6 electrons
• carbon-13
• 6 protons, 7 neutrons, 6 electrons
• carbon-14
• 6 protons, 8 neutrons, 6 electrons
HOW CAN THIS BE WRITTEN?
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There is a shorthand method for writing isotopes
It is called atomic notation
The mass number is written on the top left corner
The atomic number is written on the lower left
corner
12
6𝐶
CHARGED ATOMS ARE IONS
• Atoms are capable of gaining and losing electrons
• When they lose or gain electrons, they are called
ions
• The number of protons determines the identity of an
element
• The number of electrons can change and the
element still remain the same
• It is more common for atoms to have more or less
electrons than protons than for them to be equal to
each other
EXAMPLE
• sodium atom (Na)
• 11 protons, 12 neutrons, 11 electrons
• sodium ion (Na1+)
• 11 protons, 12 neutrons, 10 electrons
• Protons are positively charged and electrons are
negatively charged
• Ions have an unequal number of protons and
electrons
ELECTRONS DETERMINE CHEMICAL
COMBINATIONS
• Neils Bohr attempted to make a model of an atom to
help explain the chemical behavior of atoms and ions
• Protons and neutrons are found in a nucleus
• Outside the nucleus are electrons in pathways called
orbits
• Electrons have energy and can move from one orbit to
another
• The further an electron is from the nucleus, the more
energy it has
• The number of electrons found in the first three orbits is
2, 8, 8
BOHR MODEL OF THE ATOM
ENERGY AND ELECTRONS
• When an atom is energized, electrons move from a
lower energy level to a higher one
• The electrons move further away from the nucleus
• This is called an excited state
• When the electron releases its energy and moves
back to the orbit with which is came, it is said to be
in a ground state
• The number of electrons that move from one orbit
to another coupled with the orbits within which they
move give off specific colors of light
ATOMIC SPECTRA
• Every element on
the periodic table,
when given energy,
produces a unique
spectra of light
• This is how scientists
identify unknown
elements