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THE BUILDING BLOCKS OF MATTER:
ATOMS AND ELEMENTS
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• HTTPS://WWW.YOUTUBE.COM/WATCH?V=_LNF3_30LUE
ATOMS ARE. . .
• BASIS OF ALL MATTER
• SMALLEST PART OF A SINGLE
ELEMENT THAT RETAINS THE
PROPERTIES OF THE ELEMENT
PARTS OF AN ATOM
NUCLEUS
• MADE UP OF PROTONS AND NEUTRONS
• PROTONS
• HAVE A POSITIVE CHARGE(+)
• NEUTRONS
• HAVE A NEUTRAL CHARGE
ELECTRON CLOUD
• AREA AROUND NUCLEUS WHERE ELECTRONS ARE
FOUND
• ELECTRONS
• HAVE A NEGATIVE CHARGE(-)
WHY ARE ELEMENTS DIFFERENT FROM
EACH OTHER?
• ATOMS OF DIFFERENT ELEMENTS CONTAIN
DIFFERENT NUMBERS OF PROTONS
• EXAMPLE
• OXYGEN = 8 PROTONS
• COLORLESS GAS AT ROOM TEMPERATURE
• SODIUM = 11 PROTONS
• SILVERY SOFT METAL AT ROOM TEMPERATURE
• PERIODIC TABLE ORGANIZES ELEMENTS AND
PROVIDES INFORMATION
THE ATOM’S “CENTER”
• PROTONS AND NEUTRONS ARE GROUPED
TOGETHER TO FORM THE “CENTER” OR
NUCLEUS
OF AN ATOM.
Notice that the electrons are not apart of the nucleus
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ELECTRONS (-)
• NEGATIVELY CHARGED
PARTICLES
• FOUND IN ORBITS/LEVELS;
EACH ORBIT/LEVEL CAN
HOLD A MAXIMUM NUMBER
OF ELECTRONS ( 1ST = 2, 2ND = 8,
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3RD = 8 OR 18, ETC…)
• EQUAL TO THE NUMBER OF
PROTONS
• INVOLVED IN THE
FORMATION OF CHEMICAL
BONDS
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PROTONS (+)
• THE ATOMIC NUMBER EQUALS
THE NUMBER OF PROTONS IN A
SINGLE ATOM OF THE ELEMENT.
• PROTONS ARE POSITIVELY
CHARGED PARTICLES
• HELP MAKE UP THE NUCLEUS OF
THE ATOM
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• HELP IDENTIFY THE ATOM (COULD
BE CONSIDERED AN ATOM’S DNA)
• THE ATOMIC NUMBER ALSO
EQUALS THE NUMBER OF
ELECTRONS IN A SINGLE ATOM
OF THIS ELEMENT.
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ATOMIC NUMBER
• THE NUMBER OF PROTONS IN THE NUCLEUS OF AN
ATOM
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What would
be the atomic
number of this
atom?
NEUTRONS
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• NEUTRAL
PARTICLES; HAVE
NO ELECTRIC
CHARGE
• HELP MAKE UP THE
NUCLEUS OF THE
ATOM
• CONTRIBUTE TO
THE ATOMIC
MASS
Numbers on the
Periodic Table
11
Na
22.990
sodium
ATOMIC NUMBER
• NUMBER OF PROTONS IN
A SINGLE ATOM OF THIS
ELEMENT
• EQUAL TO THE NUMBER
OF ELECTRONS IN A
SINGLE ATOM OF THIS
ELEMENT
11
Symbol of the
element
Na
22.990
sodium
Name of the
element
Numbers on the
Periodic Table – cont.
11
Na
22.990
sodium
Atomic Mass
• Average mass of all
protons and neutrons
in an atom
Mass Number
• Atomic Mass rounded
to the nearest whole
number
• Number of protons +
neutrons one atom
MASS NUMBER
• THE TOTAL NUMBER OF PROTONS AND NEUTRONS IN AN
ATOM’S NUCLEUS
• EXPRESSED IN ATOMIC MASS UNITS (AMU)
• EACH PROTON OR NEUTRON HAS A MASS OF 1 AMU
What would be the mass
number of this atom?
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 3
 4
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3 protons + 4 neutrons =
a mass number of 7 amu
Why did we not account for the
electrons when calculating the
mass number?
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REMEMBER:
• ATOMIC # = PROTON # = ELECTRON #
MASS #
- ATOMIC #
= NEUTRON NUMBER
PRACTICE
ATOMIC # =
ATOMIC # =
ATOMIC MASS =
ATOMIC MASS =
MASS # =
MASS # =
# PROTONS =
# PROTONS =
# NEUTRONS =
# NEUTRONS =
# ELECTRONS =
# ELECTRONS =
BOHR MODEL OF AN ATOM
• FIRST MODEL TO HAVE A
NUCLEUS WITH PROTONS
AND NEUTRONS
• SHOWS
• ELECTRONS
• LOCATED IN ENERGY
LEVELS AROUND THE
NUCLEUS
• VALENCE ELECTRONS
• ELECTRONS IN THE
ENERGY LEVEL
FARTHEST FROM THE
NUCLEUS
BOHR MODEL OF AN ATOM
MAXIMUM NUMBER OF ELECTRONS PER ENERGY
LEVEL
PRACTICE