httpsyoutube hhbqIJZ8wCM What is an Atom The simplest particle of an element that retains its properties Who is Democritus This Greek philosopher was among the first to suggest the existence of atoms ID: 639874
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Slide1
Atomic Structure
Unit 3Slide2
What is an Atom?
https://youtu.be/
hhbqIJZ8wCMSlide3
What is an Atom?
The simplest particle of an element that retains its properties.Slide4
Who is Democritus?
This Greek philosopher was among the first to suggest the existence of atoms Slide5
What did Democritus think?
He believed that atoms were indivisible and indestructibleHe thought that atoms looked like a billiard ballSlide6Slide7
What is Dalton’s Atomic Theory?
E
lements
are composed of tiny
indivisible
particles called
atoms
Atoms of
same
element are
identical
John Dalton
(1766 – 1844)Slide8
What is Dalton’s Atomic Theory?
John Dalton
(1766 – 1844)
Atoms of different elements
can combine
in simple
ratios
to
form compounds
In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another
elementSlide9
Who discovered the electron?
J. J.
Thomson
In 1897Slide10
How did Thomson discover the electron?
A cathode raySlide11
Some Modern
Cathode Ray Tubes
Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.Slide12
What did J.J. Thomson conclude?
ALL atoms must contain
negative
particles.
He knew that atoms did not have a net negative charge and so there must be
something balancing
the negative charge.Slide13
What does Thomson’s Atomic Model look like?
Thomson believed that the electrons were scattered throughout the atom.
It
was called the “
plum pudding
” model.Slide14
What does Thomson’s ‘plum pudding’ Model look like?Slide15
Who discovered the nucleus?
Ernest Rutherford
In 1911Slide16
How did he discover the nucleus?
The Gold Foil ExperimentSlide17
What did this experiment prove?
There is a dense positive center in the atom!Slide18
What else did the Rutherford Atomic Model show?
The atom is mostly empty space
Electrons are scattered throughout the atomSlide19
What does Rutherford’s Atomic Model look like?Slide20
What is the center of the atom called?
The nucleusSlide21
What is the nucleus made up of?
The nucleus is made up of protons and neutronsSlide22
Was ALL of Dalton’s atomic theory true?
NoSlide23
What was changed from Dalton’s theory?
One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles:
Electrons, protons, and neutrons
are examples of these particlesSlide24
What are the three Subatomic Particles?
Particle
Charge
Mass (g)
Location
Electron
(e
-
)
-1
0.001
Electron cloud
Proton
(p
+
)
+1
1
Nucleus
Neutron
(n
o
)
0
1
NucleusSlide25
What is the Atomic Number?
The “atomic number” of an element is ALWAYS the number of protons
in the nucleus
***The number of protons can
NEVER
change!Slide26
Example
Element
Atomic #
# of protons
Carbon
6
6
Phosphorus
15
15
Gold
79
79Slide27
What is the Mass Number?
This is the number of protons and neutrons in the nucleus of an atomSlide28
What is the charge of an atom?
All atoms are NEUTRAL# of Protons = # of electronsSlide29
What is a Complete Symbol?
This is the symbol of the element, its mass number and its atomic number.Slide30
How do you write a complete symbol?
X
Mass
number
Atomic
number
Subscript
→
Superscript →Slide31
How is a complete symbol written on the periodic table? Slide32
Let’s try together
Find each of these:
Atomic Number
Mass Number
Br
80
35Slide33
On your own!
Find each of these:
Atomic Number
Mass NumberSlide34
How do you calculate P.E.N?
A=P=EAtomic Number
Protons
ElectronsSlide35
How do you calculate P.E.N?
M-A=NMass Number
Atomic Number
NeutronsSlide36
Let’s practice together!
If
an element has an atomic number of 34 and a mass number of 78, what is the:
number of protons
number of
electrons
number of
neutrons
complete symbolSlide37
On your own!
If an element has 91 protons and 140 neutrons what is the
Atomic number
Mass number
number of electrons
complete symbolSlide38
Symbols
If an element has 78 electrons and 117 neutrons what is the
Atomic number
Mass number
number of protons
complete symbolSlide39
Topic: Bohr Model
Essential Questions: What does an atoms structure look like?
How are electrons configured in atoms?Slide40
What is the Bohr Model?
What is the Bohr Model?
This Model shows electrons in orbit (also called energy shells) around the nucleus
P
+
: 1
E
-
: 1
N
0
:
1-1=
0
1p
+
e
nucleus
Electron Energy ShellSlide41
Constructing a Bohr Model
LET’S PRACTICE WITH NITROGEN!How do we make a Bohr Model?
Determine # protons & Neutron
draw them in inner circle
Determine # Electrons place in orbits around the nucleus as follows
1
st
orbit= 2e- max
2
nd
orbit= 8e- max
3
rd
orbit= 8e- maxSlide42
Nitrogen-14
Bohr ModelP
+
E
-
N
0
Determine # protons & Neutron
draw them in inner circle
Determine # Electrons place in energy levels as follows
1
st
energy level= 2e- max
2
nd
energy level= 8e- max
3
rd
energy level= 8e- maxSlide43
Let’s Talk About Valence Electrons
How do valence electrons effect an elements reactivity? What are Valence Electrons?
What’s the
Octet Rule
?
Electrons in the outer most shell
Determine
elements
chemical properties
Atoms gain, lose, or share electrons in order to have 8
valence electronsSlide44Slide45
Let’s Try It Together!!Slide46
Collaborate! Work With A Partner!Slide47
Exit Ticket. Try on Your Own!
Raise your hand Silently with Questions!Slide48
What is an ISOTOPE?
Atoms of the same element can have different numbers of neutrons
.
Thus, different mass numbers
.
***Remember the number of protons can NEVER change.Slide49
How do you name Isotopes?
We put the mass number after the name of the element
:
carbon-12
carbon-14
uranium-235
Mass Number here!Slide50
Example of an Isotope
Isotope
Protons
Electrons
Neutrons
Nucleus
Hydrogen–1
(protium)
1
1
0
Hydrogen-2
(deuterium)
1
1
1
Hydrogen-3
(tritium)
1
1
2Slide51
How heavy is an atom of oxygen?
It depends, because there are different kinds of oxygen atoms. (isotopes)Slide52
What is Average Atomic Mass?
The weighted average of the masses of the isotopes of an element
.Slide53
What is the unit used to Measure Atomic Mass?
The unit we use is the Atomic Mass Unit
(
amu
)Slide54
How do you calculate average atomic mass?
Step 1: Multiply the atomic mass of each isotope by it’s abundance (change to a decimal)
Step 2:
A
dd the results.Slide55
Let’s practice together
Isotope
Symbol
% in nature
Carbon-12
12
C
98.89%
Carbon-13
13
C
1.11%
Carbon-14
14
C
<0.01%
Carbon = 12.011Slide56
Example:
Element X has 2 naturally occurring isotopes. The isotope (10X) has a relative abundance of 19.91%. The isotope (11X) has a relative abundance of 80.08%. Calculate the average atomic mass of this element.