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Atomic Structure and Bohr Model
Transcript of Atomic Structure and Bohr Model
What is an atom?
in 400 B.C
Atoms are composed
of 2 regions:
: the center of the atom that contains the
of the atom
2. ELECTRON CLOUD
: the region that surrounds the nucleus that contains most of the
in the atom.
The nucleus contains 2 of the 3 subatomic particles.
PROTON: Positively charged subatomic Particle
Neutron: neutrally charged subatomic particles
The 3rd subatomic particle resides outside of the nucleus in the electron cloud.
: the subatomic particle with a
charge and relatively no mass.
Protons and neutrons live compacted in the tiny positively charged nucleus. This accounts for most of the
of the atom.
The negatively charged electrons are small and have relatively no mass but occupy a large
of space outside the nucleus.
How do the
In a neutral atom: Protons = Electrons!
protons are present in an atom, then
electrons are there to balance the overall charge of the atom -- atoms are
charge therefore they do not have to equal the # of protons or electrons.
How do we know
the # of subatomic
indicates the number of
in an atom.
Hydrogen's atomic # is 1, so hydrogen has
Carbon's Atomic #
, so carbon has
The # of
2 Protons= ??
29 Protons = ??
How do we know
the # of subatomic particles in an atom?
Number= protons + neutrons
*It is important to round the mass number to the next whole number*
Since Carbon has a mass of 12, how many neutrons does it have? Hint: The atomic number for Carbon is 6.
= Number of neutrons *
12 - 6 =
Li has a mass # of 7
and an atomic # of 3.
Protons = 3
(same as the
Neutrons = 7 - 3 = 4
Ne has a mass # of
20 and an atomic #
(20 - 10) =10
How do we determine the amount of electrons?
When the atom is
to the number of
Therefore in a neutral atom,
He has a mass # of 4
and an atomic # of 2
Determine the number of subatomic
particles in the following:
Cl has a mass
# of 35 and an atomic # of 17.
K has a mass # of 39 and an
atomic # of 19. P= ?
N = ?
39-19 = 20!
e = ?
of the Atom :)
All of the protons and neutrons
All of the electrons .
The electron cloud is divided up into energy levels.
Each energy level can hold a certain number of electrons.
The 1st energy level or shell can hold
energy level holds
The 3rd energy level holds
The 4th energy level
to 32 electrons
What does Carbon
Atomic # =?
P = ?
N = ?
E = ?
12 - 6 = 6
The Bohr Model
Atomic # =
Atomic Mass =
Mass # =
P = ?
E = ?
N = ?
84 - 36 = 48!!
1st Shell =
2nd Shell =
3rd Shell =
(36 - 28 = need 8 more)
Number of Energy Levels: 4
First Energy Level: 2
Second Energy Level: 8
Third Energy Level: 18
Fourth Energy Level: 8
For most of the time, electrons fill up the energy levels to the max capacity before moving on the the next energy level. However, sometimes levels 3 and 4 don't follow this rule. We won't be worrying about this too much in class.
**Label the atom in your notes**
round to 12