Download Atomic Structure Notes

Atomic Models
Early Greek Theories
• 350 B.C - Aristotle
• Theory that matter was made of four
“elements”: earth, fire, water, air.
• Aristotle was wrong. However, his theory
persisted for 2000 years.
Aristotle
fire
earth
air
water
Democritus
• 400 B.C. - Democritus thought matter could
not be divided indefinitely.
• This led to the idea of atoms.
John Dalton
• 1800’s
• Proposed an Atomic Theory which states;
•
•
•
•
All matter is made of atoms.
Atoms of an element are identical.
Each element has different atoms.
Atoms of different elements combine in constant
ratios to form compounds.
• Atoms are rearranged in reactions.
Jelly beans
The Electron
• Late 1800’s
• J. J. Thomson
• A gas beam was
repelled away by a
magnet.
• The gas is made of
atoms, so….
• atoms must contain
CHARGED particles!
Magnet
The beam wad
repelled (away)
Thomson’s atomic model
• Thomson found that there
were small electrons
embedded in the atom like
chocolate chips in a
chocolate chip cookie.
• Atoms are solid spheres
made-up of a solid
positive mass (cookie) with
tiny negative particles
embedded in the positive
core
Negative electrons
Positively charged cookie.
Rutherford & the Nucleus
•
•
•
•
1908
Discovered by his famous ‘gold foil’ experiment.
He shot positively charged particles at a very thin piece of gold foil.
He expected the particles to go right through. Most did go through
or got deflected.
• But a few
BOUNCED
BACK!
•THEY HIT
SOMETHING
SOLID!
Rutherford’s gold foil experiment
•
•
•
•
This proved that:
the atom had a dense but very small positive core
the electrons were far away from the nucleus
Most of the atom is just EMPTY SPACE!
That would be like a basketball (nucleus) on the 50 yard line,
and you were an electron in a seat way up in the stands.
Neils Bohr
• Early 1900’s
• Electrons move in orbits, energy levels
• Electrons in Definite energy Levels around the
nucleus
• Electrons can move to
different energy levels if
they gain or lose energy.
Quantum Mechanical Model
or Electron Cloud Model
• Electrons move around the nucleus very fast.
•You can’t predict where an electron will be at any moment.
•The analogy here is that of a "beehive" where the bees are
the
electrons and they ‘buzz’ around the nucleus.
ATOMS AND
ELEMENTS
ATOMIC STRUCTURE
MATTER….
Is Everything!
 It’s the amount of mass in an object



It has volume: takes up space


Measured in kilograms
Measured in milliliters or cubic centimeters
All matter is composed of elements

88 natural elements
ELEMENTS ARE…
Purest of the pure substances
 There are 112 of them known so far
 They are organized on the Periodic Table
 The most common elements:

1. oxygen. ( air, water, rock, living things)
2. Hydrogen (water, living things, sun, stars)
3. Nitrogen (air 80%, living things, soil)
4. magnesium, iron, aluminum, carbon
AGENDA 3/21
Notes on atomic structure
 Atoms worksheet

EVERY ELEMENT ON THE PERIODIC TABLE IS ASSIGNED A
BOX WITH SPECIFIC INFORMATION IN IT.
ATOMIC SYMBOL
1
or two letter symbol
 First letter is always CAPITOL, second letter
always lower case.
Co (cobalt) is not same as CO (carbon monoxide)
 Examples:
C for carbon
 Ca for calcium
 Cl for chlorine
 Cf for californium

CF C
F
Cf
Not correct!!!
ATOMS
 Smallest

part of an element.
Too small to be seen.
 All
atoms are made of the same basic
‘ingredients’
 Atoms vary in size and mass.

Atoms are made up of:
Protons (+ charge)
 Electrons (-charge)
 Neutrons (neutral)

PROTON
 Dense,
positively charged particle
 There
are equal # of protons and electrons in a
neutral atom.
+ = -
 Proton’s
 Proton
mass = 1 amu
# is their Atomic number.
Ex: 6 protons is element 6 or carbon
NEUTRON
 Difficult


to ‘find’ because they have no charge
Same mass as a proton (1 amu),
but has NO CHARGE (neutral)
Neutrons are in the nucleus.
No
charge
NEUTRAL
ATOMS
Since protons are positively charged
 And electrons are negatively charged,


A neutral atom has EQUAL # protons and electrons!
+
=
Ex: chlorine 17 protons
-
17 electrons
MASS NUMBER



Mass Number = # protons + # neutrons in nucleus
Protons and neutrons make up the mass of the
nucleus (and 99.9% of the atom’s mass)
Ex: Chlorine’s mass number is 35
17 protons and 18 neutron = 35
NUMBER OF NEUTRONS
Mass number of oxygen
atomic number (protons)
number of neutrons
16
-8
8
Mass number of uranium
atomic number (protons)
number of neutrons
* The number of neutrons in an atom can vary.
238
-92
146
WORKSHEET
AGENDA 3/22
Notes on isotopes
 Isotope worksheet

THERE ARE TWO FORMS OF CARBON…
Carbon- 14 has
Carbon-12 has
6 protons
+6 neutrons
Total mass = 12
6 protons
+8 neutrons
________________
Total mass = 14
Carbon-12 and Carbon-14 are Isotopes.
So… what is an isotope?
ISOTOPE


Atoms of the same element with a different
number of neutrons
So…
Same # of Protons
 Different # neutrons
 Different mass number

Element
lithium
Number of Number of Number of
Protons
Neutrons Electrons
3
silver
6
17
35
61
108
47
207
Lead
calcium
Atomic
Number
3
6
carbon
chlorine
4
Mass
Number
20
20
Periodic Table of Elements
Dmitri Mendeleev
□ First Table made by arranging the 63
known elements in order of
□ atomic weight
□ grouping them by similarity of properties.
□ Predicted
□ the existence of new elements
□ pointed out that some of the known
atomic weights were wrong
□ He left space on his table for new
elements, and predicted yet-to-bediscovered elements
Aren’t you glad it
doesn’t look like this now?
This gives me a headache.
Gaps where he knew that
missing elements should be.
The Modern Periodic Table
□ What season comes after our current season?
After that?
□ The periodic tables has:
□ Horizontal Rows (label these from top to
bottom #’s 1 through 7. The row number
corresponds to how many energy levels the atom in that
row have.)
□ These rows show TRENDS!
□ For example, as you move across a row, elements go
from metallic to less metallic.
□ When you finish a row, the next row repeats those
properties. Just like the seasons repeat themselves
year after year.
MORE about the P.T. !
□ What are some things you have in common with
your family?
□ The periodic table also has
COLUMNS. They are called:
□ Groups or Families –
□ Elements in the same group have similar
physical and chemical properties
http://www.youtube.com/watch?v=f3p8pa
K24ac
More about Groups on the P.T.
□ The groups can be labeled 1 through
18 (most modern way)
□ or 1A, 1B, 3B, 4B, etc. (old-fashioned)
□ Groups with an A have a “little of
everything” metal, non-metal, reactive,
non-reactive
□ Groups with a B are “transition metals”
and pretty much alike.
Hey! Label your table!
1
2
3
H
He
1
2
Li
Be
B
C
3
4
5
Na Mg
11
4
K
19
5
7
Ca Sc
O
F
Ne
6
7
8
9
10
Al
Si
P
S
Cl
Ar
13
14
15
16
17
18
Ti
V
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
Kr
23
24
35
36
I
Xe
53
54
20
21
22
Rb Sr
Y
Zr Nb Mo Tc Ru Rh Pd Ag Cd
In
39
40
41
42
49
Hf
Ta
W
72
73
74
37
6
12
N
38
Cs Ba
55
56
Fr
Ra
87
88
Nonmetals
25
26
27
28
29
30
METALS
43
44
Re Os
75
76
47
45
46
Ir
Pt Au Hg
Tl
77
78
81
79
48
31
80
32
33
34
Sn Sb Te
50
51
Pb Bi
82
83
52
Po At Rn
84
85
86
Rf Db Sg Bh Hs Mt
104
105
106
107
108
Metalloids
109
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
57
58
59
Ac Th Pa
89
90
91
60
U
92
61
62
63
64
65
66
Np Pu Am Cm Bk Cf
93
94
95
96
97
98
67
68
69
70
71
Es Fm Md No Lr
99
100
101
102
103
And color code, too!
Come get three colored pencils but you don’t’ have to use these offensive colors.
1
Nonmetals
2
3
4
5
Metals
6
7
Metalloids
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 349
Properties of Metals,
Nonmetals, and Metalloids
METALS
malleable, lustrous, ductile, good conductors of heat and electricity
NONMETALS
gases or brittle solids at room temperature, poor
conductors of heat and electricity (insulators)
METALLOIDS
(Semi-metals)
dull, brittle, semi-conductors (used in computer chips)
Periodic Trends
□ Wow! Can’t you just wait?
□ The periodic table shows all sorts of
trends, but we will keep it very basic.
Atomic size
(radius)
□ The size of the
atom
increases as
you go down
the table.
□ Size decreases
as you go
across.
Electronegativity - the tendency
of an atom to attract electrons
Ionization Energy - the amount of
energy required to remove an
electron from the atom or molecule
Electron Affinity - the amount of energy
released when an electron is added to a
neutral atom or molecule to form a
negative ion.
Melting/Boiling Point
Highest in the middle of a period.
1
2
3
4
5
6
7
The elements get more metallic as you go
down the table, and less metallic as you go
across.