Download Structure of the Atom

9/29/2008
Structure of the Atom
Nucleus
• Center of atom
• Positively charged
• Contains the “mass”
of the atom
• Contains subatomic
particles
Subatomic Particles in
Nucleus
• Protons - positive
charge
• Neutron - neutral
charge (no charge)
• Protons + Neutrons =
Mass Number
Element Identity
• Elements are made up
of only one type of atom
• The number of
protons an element
has determines the
type of atom it is.
• Number of protons =
atomic number
Electron Cloud
• Surrounds Nucleus
• Subatomic particle
in electron cloud electrons
• Electrons - negative
charge
For example:
• Carbon’s atomic
number is 6;
therefore Carbon
has 6 protons.
• How many protons
does hydrogen
have?
• How many protons
does Oxygen have?
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Atomic Mass
• Measured in atomic
mass unit (amu)
• Mass number - atomic
mass rounded.
• For example: Average
atomic mass of
Potassium is 39.098
Mass number = 39
• What is the mass number
of Boron?
Practice
• How many neutrons
does Calcium have?
Mass number = ___
Protons = ____
Mass number minus
protons = _____
How many neutrons
does Xenon have?
Practice
• How many electrons
does Neon have?
• Remember atomic
number tells you
how many protons
the atom has.
Neon’s atomic number
is 10; therefore it
has 10 protons and
10 electrons.
Calculating Neutrons
• IF protons + neutrons =
Mass Number
• THEN Mass Number
minus protons = neutrons
• For example:
11 + n = 23 or
• 23 - 11 = n
n = 12,
• sodium has 12 neutrons
Calculating Electrons
• Atoms that are stable
have no electrical
charge; therefore,
protons must equal
electrons.
• For example: Sodium
has 11 protons and 11
electrons.
(The positives must equal
the negatives. )
Atomic Model
• Diagram representing the
subatomic particles in an
atom.
• Begin by filling in protons
and neutrons in the
nucleus (the center)
• Place electrons around the
nucleus
• Electrons are distributed in
the electron cloud in levels
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9/29/2008
Electron Cloud Levels
• 1st Level can only hold
2 electrons
• 2nd Level can only
hold 8 electrons
• 3rd Level can hold up
to 18 electrons
Electron Cloud Levels
Sulfur has ___
electrons.
2 will fill into the 1st
energy level
8 will fill into the 2nd
energy level
6 will fill into the 3rd
energy level.
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