science 9 models of the atom. all atoms are not created equal atoms can vary from one to the next of...
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S C I E N C E 9
MODELS OF THE ATOM
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?
• 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
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