Transcript Atomic structure

Warm-up Quiz
Please write the name of the following
elements on p 34
Then write the Agenda and LG


I.
II.
III.
IV.
V.
VI.
Pu
Pt
Sn
Sc
S
Na
S.MORRIS 2006
The smallest particle of an element that
retains the properties of the element is
called an atom.
 Atoms are extremely small (a copper atom
has a diameter of 0.000000000128 m)
 Atoms can be seen using a scanning
tunneling microscope.

HISTORY OF THE ATOM
460 BC
Democritus develops the idea of atoms
Matter is composed of empty space
through which solid atoms move
ATOMA
(greek for indivisible)

384-322 BC Aristotle
◦ One of the most influential philosophers
◦ Criticized Democritus, saying that he did not
believe that the nothingness of empty space
could exist
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
Dalton created the atomic theory model:
1.
2.
3.
4.
All elements are composed of tiny,
indivisible particles called “atoms”
Atoms of the same elements are identical.
*Each element is unique
Atoms of different elements can physically
mix or chemically combine (forming
compounds)
Chemical reactions occur when atoms are
separated, joined, or rearranged
Much of his theory is still accepted.
HISTORY OF THE ATOM
1886 – E. Goldstein discovered
positive particles in atoms.
He observed rays traveling in the
opposite direction of cathode rays.
These particles were termed
“protons” (p+) by Ernest Rutherford
in 1920.
HISTORY OF THE ATOM
1898
Joseph John Thompson
passed electric current through a glass filled
with gas. He discovered that a beam of
negative charges travelled from the cathode
(-) to the anode (+)
Joseph John Thompson
He called these smaller negative particles
ELECTRONS
HISTORY OF THE ATOM
1904
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
PLUM PUDDING
MODEL
like plums surrounded by pudding.
HISTORY OF THE ATOM
1910
Ernest Rutherford
oversaw Geiger and Marsden carrying out his
famous gold foil experiment.
they fired Helium nuclei at a piece of gold foil
which was only a few atoms thick.
they found that although most of them
passed through. About 1 in 10,000 were
deflected and, to their surprise, bounced
straight back
HISTORY OF THE ATOM
This experiment caused Rutherford to
conclude:
1. Atoms are mostly space
2. Atoms have a solid nucleus at the
center which contains most of the
mass
This overturned the “plum pudding model”
of the time.
HISTORY OF THE ATOM
helium nuclei
They found that while most of the helium nuclei passed
through the foil, a small number were deflected and, to their
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
HISTORY OF THE ATOM
1913
Niels Bohr
studied under Rutherford at the Victoria
University in Manchester—parachuting into
England after escaping the German
invasion of Denmark.
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. Each
orbit has a fixed energy level and therefore
the electrons do not lose energy.
1931 - James Chadwick

Discovered the neutron, the neutral
subatomic particle in the nucleus
Warm-up P 4 – Page 36-37
SHOW WORK!
lsotope copy LG & agenda

1. If my product has a ∆H of 50 and my reactant
has a ∆ H of 20, is this an endothermic or
exothermic reaction?

2. A student placed citric acid into water, and the
temperature fell from 60.2 °C to 50.2 °C for
40.00 g of water, how many joules were
absorbed? The specific heat of water is 4.12 J/g
°C.
ATOMIC STRUCTURE
Subatomic particles
Particle
Charge
Mass
Location
proton
+ charge
1 AMU
nucleus
No charge 1 AMU
nucleus
neutron
electron
- charge
Nil (0)
AMU
Orbitals
/electron
cloud
Subatomic Particles
The nucleus is the tiny positive core of the atom which
contains most of the mass of the atom.
The proton (p+) is the positively (1+) charged particle
found in the nucleus of the atom.
The neutron (no) is the particle with no charge (0) found
in the nucleus of the atom.
Subatomic Particles

The electron (e-) is the negatively (1-)
charged particle found in the electron cloud
outside of the nucleus.
ATOMIC STRUCTURE
He
2
Atomic number
the number of protons in an atom
Identifies the element
4
Atomic mass
the number of protons and
neutrons in an atom
Mass of the nucleus
number of electrons = number of protons
Atomic number =
Protons =
Electrons
Mass number Atomic number =
Neutrons

Since an atom is electrically neutral, the
number of protons equals the number of
electrons.

Atomic # = # of protons = # of electrons
Element
Protons
electrons
Pb
Atomic
Number
82
?
?
?
?
8
?
?
?
?
30
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Neutrons = Atomic mass – Atomic number
Element
Atomic mass
Atomic number
Neutrons
Potassium
39
19
20
Boron
11
5
6
Argon
40
18
22
Warm-up – Page 36-37
SHOW WORK!
Also copy LG & agenda

1. My product has a H of 50J and my reactant
has a ∆H of 20J, is this ∆H an endothermic or
exothermic reaction?

2. A student placed citric acid into water, and the
temperature fell from 60.2 °C to 50.2 °C for
40.00 g of water, how many joules were
absorbed? The specific heat of water is 4.12 J/g
°C.
When you are done . . .
Please place test and answer sheet in
appropriate stacks at the front
 Get new Atomic Structure practice and
use your periodic table to fill it out.
 Please also get out your note packet from
last class, as we will fill in another short
section today.

When you are done . . .
Please place test and answer sheet in
appropriate stacks at the front
 Get new Atomic Structure practice and
use your periodic table to fill it out.
 Ms. Matte will call you to the front
individually to see your test grade.

Benchmark
Do not write on the test.
 You may use your own periodic table
 You may get a blank sheet of notebook
paper for scratch paper
 Please use a pencil

Please get out your note packet from last
class, as we will fill in another short
section today.
 Copy down the Learning Goal and
Agenda.
 We will do the Benchmark after Lunch in
period 6


Ions are charged atoms
• Anion – atom gains an electron giving it a
negative charge
• Cation – atom loses an electron giving it a
positive charge
Oh no
Protons
Never
Change!!!!
Ion
Atomic
Number
Atomic
Mass
Number
Protons
Neutrons
Electrons
Mg 2+
12
24
12
12
10
Ag 2+
47
108
47
61
45
S 2-
16
32
16
16
18
Cl 1-
17
35
17
18
18
Ion
Atomic
Number
Atomic
Mass
Number
Protons
Neutrons
Electrons
M 2+
12
24
12
12
10
Ag 2+
47
108
47
61
45
S 2-
16
32
16
16
18
Cl 1-
17
35
17
18
19
Isotopes are atoms that have
the same number of protons but
different numbers of neutrons.
All isotopes have the chemical
properties of that element.

In order to identify the various isotopes of an
element, chemists add a number after the
elements name. The number added is called the
mass number and it represents the sum of the
number of protons and neutrons in the nucleus.
Potassium-39 Potassium-40 Potassium-41
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P+
19

No
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E-
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Number of neutrons = mass number – atomic number
20
19
19
21
19
19
22
19
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
Atomic mass of an element is the weighted average
mass of the isotopes of that element.
Unit is amu
Example: The atomic mass of Chlorine (Cl) is 35.5 amu.
Chlorine exists naturally as 75% chlorine-35 and 25%
chlorine–37
75% = 75/100=.75
25% = 25/100=.25
.75 x 35 amu = 26.25 amu
.25 x 37 amu = 9.25 amu
Weighted average atomic mass of Cl =
(26.25 + 9.25) = 35.5 amu
• Ex...
Natural copper (Cu) consists of 2 isotopes ...
Copper – 63
Copper – 65
69%
31%
• To calculate avg. mass...
Step 1 : mass x abundance for each isotope
Step 2 : add the two values from step 1 together
63 x .69 =
43.47
43.47
+20.15
65 x .31 =
20.15
63.62 amu
Isotopic Symbol
X = element symbol
 A = mass number
 Z = atomic number
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