Download e - Humble ISD

HHS-CHEM-2010/11
Chapter 4- page 86
“The Structure of the Atom”
Chemistry
Humble High School
Ms . B
Section 4.1 Early Theories of Matters
HISTORY OF THE ATOM
Read p- 88 from “ The greek philosophers Democritus…to…John
Dalton”.
• Describe
Which of Dalton’s beliefs about the atom are wrong?
Explain why.
• Explain Why were alpha particles deflected in Rutherford’s gold foil
experiment?
• Identify
HISTORY OF THE ATOM
460 BC
Democritus develops the idea of atoms
he pounded up materials in his pestle and
mortar until he had reduced them to smaller
and smaller particles which he called
ATOMA
(greek for indivisible)
HISTORY OF THE ATOM
1808
John Dalton
suggested that all matter was made up of
tiny spheres that were able to bounce around
with perfect elasticity and called them
ATOMS
HISTORY OF THE ATOM
1898
Joseph John Thompson
found that atoms could sometimes eject a far
smaller negative particle which he called an
ELECTRON
HISTORY OF THE ATOM
1904
Joseph John Thompson
Thompson develops the idea that an atom was made up of
electrons scattered unevenly within an elastic sphere surrounded
by a soup of positive charge to balance the electron's charge
like plums surrounded by pudding.
PLUM PUDDING
MODEL
HISTORY OF THE ATOM
1910
Ernest Rutherford
He fired Helium nuclei at a piece of gold foil
which was only a few atoms thick.
He found that although most of them passed
through. About 1 in 10,000 hit and bounced
back.
HISTORY OF THE ATOM
gold foil
helium nuclei
He found that while most of the helium nuclei passed through
the foil, a small number were deflected and, to his surprise,
some helium nuclei bounced straight back.
HISTORY OF THE ATOM
Rutherford’s new evidence allowed him to propose a more
detailed model with a central nucleus.
He suggested that the positive charge was all in a central
nucleus. With this holding the electrons in place by electrical
attraction
However, this was not the end of the story.
Rutherford’s problem:
In the following pictures, there is a target
hidden by a cloud. To figure out the shape of
the target, we shot some beams into the cloud
and recorded where the beams came out. Can
you figure out the shape of the target?
Target
#1
Target
#2
The Answers:
Target #1
Target #2
HISTORY OF THE ATOM
1913
Niels Bohr
studied under Rutherford at the Victoria
University in Manchester.
Bohr refined Rutherford's idea by adding
that the electrons were in orbits. Rather
like planets orbiting the sun. With each
orbit only able to contain a set number of
electrons.
Bohr’s Atom
electrons in orbits
nucleus
PLANETERE
MODEL
I’m an electron!
I’m a proton!
I’m a neutron!
I was walking along and I saw these two.
I was telling jokes to the neutron.
The proton and I were having fun.
They looked so happy there together.
I was p o s i t i v e l y charged!
I couldn’t have amassed more happiness.
The proton looked happy, so I wandered closer.
I could see the electron coming near.
The who? Huh?
They were HUGE next to me!
The electron was so tiny!! so cute!
Like a speck of dust, or something…
I didn’t want to seem noisy, so I kept walking.
Around and around the electron goes.
Hey electron, you’re making the proton dizzy.
The proton seems so happy with the neutron.
I’m having fun, but I still notice the electron.
It won’t bother me if the electron hangs around.
I guess I’ll just wander around out here.
I’m happy hanging out here.
The center is cool, but sometimes it can be a “Bohring”.
Electrons circle around the nucleus of an atom.
Protons are a main part of the nucleus of an atom.
Neutrons also hang out in the nucleus of an atom.
Electrons have a negative charge. 
Protons have a positive charge. +
Neutrons have no charge.
0
Electrons are little and have a mass of almost zero.
Protons are big and have a mass of one.
Neutrons are also big and have a mass of one.
What is an atom ?
• Definition : p- 90. Read Defining an atom.
Sec4.2 Subatomic Particles and the
Nuclear Atom
• Nucleus :center of the atom and Home of
Protons and Neutrons.
*Proton = atomic number
• Has a positive (+) charge
• Has a relative mass of 1
• Determines the Element
• Found inside the nucleus
What is the structure of an
atom?
*Neutron
• Has no (0) charge
• Has a relative mass of 1
• Determines the isotope
–Isotopes are two of the same
element with different masses
• Found inside the nucleus
What is the structure of an
atom?
• Electron
– Has a negative (-) charge
– Has a relative mass of 0 (zero)
– Determines the ion
– Found outside the nucleus
• Bohr model – electrons are in specific
energy levels
• Electron cloud model – electrons are in
a random cloud
HELIUM ATOM
Shell
proton
+
-
N
N
+
electron
What do these particles consist of?
-
neutron
ATOMIC STRUCTURE
Particle
Charge
Electron
(e-)
-1
Mass (g) or
amu
9.11 x 10-28
Or 0 amu
+1
1.67 x 10-24
Or 1 amu
Nucleus
0
1.67 x 10-24
Or 1 amu
Nucleus
Proton
(p+)
Neutron
(no)
Location
Electron
cloud
Sect.4.3 How Atoms Differ
Atomic number of an element is the number of
protons in the nucleus of each atom of that
element : it is what define an element
Element
# of protons
Atomic #
Carbon
6
6
Nitrogen
7
7
Oxygen
8
8
Sect.4.3 How Atoms Differ
Mass number is the number of protons and
neutrons in the nucleus of an isotope:
Mass # = p+ + n0
Nuclide
Oxygen - 18
Oxygen
- 16
Phosphorus - 31
p+
n0
Mass #
8
10
18
8
8
16
15
16
31
What is a chemical symbol?
• Chemical symbol tells us what atom it is
• Always a CAPITAL LETTER, sometimes
followed by a lower case letter
• Ex: Oxygen O; Nitrogen N; Sodium Na
• Copper Cu; Iron Fe
• Cobalt Co; Carbon Monoxide CO
• (Co is an element, CO is a compound)
ATOMIC STRUCTURE
4
2
He
Atomic mass (superscript)
the number of protons and
neutrons in an atom
Atomic number (subscript)
the number of protons in an atom
number of electrons = number of protons
Hint: mass # is always › Atomic #
Symbols

Br
Find each of these:
a) number of protons:
b) number of neutrons:
c) number of electrons:
d) Atomic number:
e) Mass Number:
Bromine
Symbols

If an element has an atomic
number of 34 and a mass
number of 78, what is the:
a) number of protons:
b) number of neutrons:
c) number of electrons:
d) complete symbol:
Symbols
 If an element has 91
protons and 140 neutrons
what is the
a) Atomic number:
b) Mass number:
c) number of electrons:
d) complete symbol:
Symbols
 If an element has 78
electrons and 117 neutrons
what is the
a) Atomic number:
b) Mass number:
c) number of protons:
d) complete symbol:
Isotopes
• Dalton was wrong about all
elements of the same type being
identical
• Atoms of the same element can
have different numbers of
neutrons.
• Thus, different mass numbers.
• These are called isotopes.
Naming Isotopes
• We can also put the mass
number after the name of the
element:
carbon-12
carbon-14
uranium-235
Isotopes are atoms of the same element having
different masses, due to varying numbers of
neutrons.
Isotope
Hydrogen–1
(protium)
Hydrogen-2
(deuterium)
Hydrogen-3
(tritium)
Protons Electrons
Neutrons
1
1
0
1
1
1
1
1
2
Nucleus
Isotopes
Elements
occur in
nature as
mixtures of
isotopes.
Isotopes are
atoms of the
same element
that differ in
the number of
neutrons.
Calculating Atomic Mass
• Problem 4-3 page 103
• Practice problems # 15-16 page 104
The Atomic Structure - Atomic Math
Challenge
Atomic Number
Symbol
Name
Atomic Mass
Atomic number equals the number of
Atomic mass equals the number of
protons
protons
or
+
electrons .
neutrons
Assignment: Finish the rest of the worksheet and turn it in to your
teacher.
The first energy street can hold only
two Electron. The second energy
street, called the Energy Freeway,
can hold 8 electrons. The third
energy street, called the Energy
Superhighway, can hold 18 of them .
Energy Superhighway Can
hold 18 electrons( 2,6,10)
Energy Freeway
Can hold 8 (2,6)
Energy Street
Can hold 2
electrons
Nucleus Arcade
Contains protons & neutrons
ATOMIC STRUCTURE
There are two ways to represent the atomic
structure of an element or compound;
1.
2.
Electronic Configuration
Dot & Cross Diagrams
ELECTRONIC CONFIGURATION
With electronic configuration elements are represented
numerically by the number of electrons in their shells
and number of shells. For example:
We know
2e in
1st
shell
2
+
Nitrogen
14
5 = 7
7
5e in 2nd shell
So,
Nitrogen
configuration = 2 , 5
N
ELECTRONIC CONFIGURATION
Write the electronic configuration for the following
elements;
a)
B
11
5
b)
2,3
d)
Cl
35
17
2,8,7
Na
23
11
c)
2,8,1
e)
Si
28
14
2,8,4
O
16
8
2,6
f)
Ca
40
20
2,8,8,2
DOT & CROSS DIAGRAMS
With Dot & Cross diagrams elements and compounds
are represented by Dots or Crosses to show electrons,
and circles to show the shells. For example;
X
Nitrogen
X X
N
XX
X X
N
7
14
DOT & CROSS DIAGRAMS
Draw the Dot & Cross diagrams for the following
elements;
X
8
17
X
a) O
b)
Cl 35 X
16
X
X
X
X
X
X
X X X Cl X X
X
X
X
O
X
X
X
X
X
X
X
X
X
SUMMARY
1. The building block of Matters is Atom; Definition of an atom
2. The subatomic particles are: Proton, Neutron, Electron.
3. a) Protons are +ve and defines the Element.
b) Neutrons are neutral and defines the isotopes.
c) Electrons are –ve and defines the chemical properties of the element.
4. Isotopes are atoms of the same element that differ in the number of
neutrons.
5. The Atomic Number of an atom = number of protons in the nucleus.
6. The Atomic Mass of an atom = number of P + N in the nucleus.
7.
8.
The number of Protons = Number of Electrons= overall charge = 0
Electrons orbit the nucleus in shells.
9.
Each shell can only carry a set number of electrons= 2,8,18
ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or
Shells around the nucleus of an atom.
•
first shell
a maximum of 2 electrons
•
second shell
a maximum of 8 (2,6) electrons
•
third shell
a maximum of 18 (2,6,10) electrons
Chapter 5 p-116
Electrons in Atoms
• Read p-118