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Atomic Structure and Bohr Model

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by

Emily Holdsworth

on 2 May 2016

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Transcript of Atomic Structure and Bohr Model

Atom: The smallest unit of matter that retains the identity of the substance.
What is an atom?
First
Proposed by
Democritus
in 400 B.C
The Atomic
Structure

Atoms are composed
of 2 regions:
1. NUCLEUS
: the center of the atom that contains the
mass
of the atom
2. ELECTRON CLOUD
: the region that surrounds the nucleus that contains most of the
space
in the atom.
What's
in the
Nucleus?

The nucleus contains 2 of the 3 subatomic particles.
PROTON: Positively charged subatomic Particle
Neutron: neutrally charged subatomic particles
What's in
the
electron
cloud?
The 3rd subatomic particle resides outside of the nucleus in the electron cloud.
Electron
: the subatomic particle with a
negative
charge and relatively no mass.
How do
these
particles
interact?
Protons and neutrons live compacted in the tiny positively charged nucleus. This accounts for most of the
mass
of the atom.
The negatively charged electrons are small and have relatively no mass but occupy a large
volume
of space outside the nucleus.
How do the
subatomic
particles
balance
each other?

In a neutral atom: Protons = Electrons!
If
20
protons are present in an atom, then
20
electrons are there to balance the overall charge of the atom -- atoms are
Neutral!
Neutrons have
no
charge therefore they do not have to equal the # of protons or electrons.
How do we know
the # of subatomic
particles in
an atom?

Atomic Number:
indicates the number of
protons
in an atom.
Example:
Hydrogen's atomic # is 1, so hydrogen has
1
proton.
Example:
Carbon's Atomic #
is
6
, so carbon has
6
protons.
The # of
Protons

identifies
the atom!
2 Protons= ??
HELIUM!
29 Protons = ??
COPPER!!
How do we know
the # of subatomic particles in an atom?
Mass
Number= protons + neutrons

*It is important to round the mass number to the next whole number*
E
Example:
Since Carbon has a mass of 12, how many neutrons does it have? Hint: The atomic number for Carbon is 6.
Mass #
-
Protons
= Number of neutrons *
12 - 6 =
6 Neutrons
Determining
the number
of protons
and neutrons.
Li has a mass # of 7
and an atomic # of 3.
Protons = 3
(same as the
atomic
number)
Neutrons = 7 - 3 = 4
(
mass
# -
atomic
#)
Ne has a mass # of
20 and an atomic #
of 10.
Protons =
10
Neutrons =
(20 - 10) =10
How do we determine the amount of electrons?
When the atom is
neutral
, the
electrons
are
equal
to the number of
protons
.
Therefore in a neutral atom,
Electrons
=
Protons
=
Atomic Number
Example:
He has a mass # of 4
and an atomic # of 2
P=
2
N=
2
E=
2
Determine the number of subatomic
particles in the following:
Cl has a mass
# of 35 and an atomic # of 17.
P= ?
17
n= ?
35 -17
=18!
e= ?
17
K has a mass # of 39 and an
atomic # of 19. P= ?
19
N = ?
39-19 = 20!
e = ?
How exactly
are the
particles
arranged?

Bohr Model
of the Atom :)
Nucleus:
All of the protons and neutrons

Electron Cloud:
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
2 electrons
The second
energy level holds
8 electrons
The 3rd energy level holds
18
electrons
The 4th energy level
can
hold
up
to 32 electrons
.
What does Carbon
look like?
Mass#?
12
Atomic # =?
6
P = ?
N = ?
E = ?
6
12 - 6 = 6
6 p
6 n
The Bohr Model
and Atomic
Structure
Elements Name=
Krypton
Symbol=
Kr
Atomic # =
36
Atomic Mass =
83.80
Mass # =
84
P = ?
E = ?
N = ?
36
36
84 - 36 = 48!!
1st Shell =
2 electrons
2nd Shell =
8 electrons
(10 total)
3rd Shell =
18 electrons
(28 total)
4th Shell:
(36 - 28 = need 8 more)
8 electrons!
ALL DONE!
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
Full transcript