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ATOMS
The smallest unit of an element that retains properties of
the element.
History of the Atom
John Dalton
Matter is made up of atoms
Atoms cannot be divided.
All atoms of the same element are
alike.
Different elements are made of
different atoms.
Thomson
Described atom as a positive
ball with negative electrons spread
evenly throughout.
Rutherford
Said an atom had a
positive nucleus with negative
electrons orbiting it- it had NO
NEUTRONS.
History of Atom continuedElectron Cloud Model
Electrons form a cloud around the
nucleus.
Bohr
Bohr’s model had a nucleus
containing protons and
neutrons. The electrons
orbited on energy levels.
This is the model we use in class.
This is the accepted model and
allows for the unpredictable
wave nature of electrons.
Atomic Structure
The smallest unit of an element is an atom. (Anything
smaller is not an atom!)
Atoms have 3 structural parts
Protons
Neutrons
Electrons
Protons
Atomic number
Have a positive charge
Are located in the nucleus
Chemical symbol
Give an atom its identity
Element
Equal to the atomic number
Atomic mass
Neutrons
Have NO charge (NEUTRAL)
Are located in the nucleus
Mass = protons + neutrons
● Round the atomic mass to
nearest whole number
(14.007 to 14)
● Subtract the number of
protons from the mass
(14 - 7)
● There are 7 neutrons
To determine the number of neutrons, subtract
the number of protons (atomic number) from
the atomic massThe NEWS about atomsNEUTRAL NEUTRONS are in the NUCLEUS!
Electrons
Smallest, lightest particle
Located outside the nucleus in the electron cloud
Equal to the number of protons in a neutral atom
(6th grade assumes all atoms are neutral)
Negatively charged
When drawing an atom, each shell or
energy level is ONE row on the periodic
table.
(Row 1 has 2 elements- Energy level 1 has
2 electrons. Row 2 has 8 elements - Energy
level 2 has 8 electrons.)
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
boron
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
neutrons
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
boron
B
atomic
number
atomic mass
number of
protons
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
neutrons
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
boron
B
5
atomic mass
number of
protons
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
neutrons
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
boron
B
5
11
number of
protons
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
neutrons
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
boron
B
5
11
5
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
neutrons
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
number of
neutrons
boron
B
5
11
5
6
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
number of
electrons
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
number of
neutrons
number of
electrons
boron
B
5
11
5
6
5
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
number of
neutrons
number of
electrons
boron
B
5
11
5
6
5
carbon
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
Let’s Practice! (p6 in IA Notebook)
element
symbol
atomic
number
atomic mass
number of
protons
number of
neutrons
number of
electrons
boron
B
5
11
5
6
5
carbon
C
6
12
6
6
6
● DON’T FORGET to ROUND the ATOMIC MASS!!
● REMEMBER
○ Atomic number = protons
○ Electrons = protons (in a neutral atom)
○ Mass = protons + neutrons
● Chemical symbols are ALWAYS Capital/ lower-case
letters!
Elements
Simplest form of matter
Made up of only ONE type of atom
Atoms of an element are basically alike (ALWAYS have the same
number of PROTONS), but the number of NEUTRONS may vary
(ISOTOPES)
Can be represented by a chemical symbol. (Chemical symbols are 1
- 2 letters. The first is always CAPITALIZED and second is
LOWER-CASE)
Isotopes of Hydrogen
Atomic Number 1
Atomic Mass 1
Atomic Number 1
Atomic Mass 2
Atomic Number 1
Atomic Mass 3
Most Common
Elements
There
are a little over 100 elements found in nature.
A limited number of those form the largest part of Earth’s
crust, living matter, the oceans, and the atmosphere.
Water- hydrogen and oxygen
Air- nitrogen and oxygen
Living things- carbon, hydrogen, and oxygen
Most common elements are- aluminum, calcium, carbon,
hydrogen, iron, magnesium, nitrogen, oxygen, potassium,
silicon, sodium
Earth’s crust- oxygen, aluminum, and silicon