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Chapter 6
ATOMIC MODELS
Atoms are made of smaller particles:
MATTER, PROPERTIES,
AND PHASES
MATTER and ATOMS
MATTER describes everything that we
can see, touch, smell, or feel. In other
words, mat ter is anything that has mass
and takes up space (including air and
almost everything else).
The smallest unit of matter is called an
ATOM. If you chop a piece of metal into
a bajillion pieces, the smallest bit you are
left with that still has the properties of
PROTONS (positively charged particles)
NEUTRONS (electrically neutral particles,
which means it has no charge),
ELECTRONS (negatively charged particles with almost no mass)
matter
anything that
has mass and
takes up space
atom
nucleus
the smallest
unit of matter
The word "a tom" is
derived from a Greek
word that means
“cannot be divided.”
the metal is called an atom.
the center of an
atom, formed by
protons and neutrons
Protons and neutrons stick
together to form the center
of an atom, called the
NUCLEUS, which has a net
positive charge. Electrons
(and the Greeks
didn't even have a
particle accelerator!)
60
(Remember a “model” is a
way to represent something
th at we can’t easily see.)
orbit, or circle around, the
nucleus, but too quickly to
The MODERN ATOMIC MODEL
shows an ELECTRON CLOUD rather
than individual electrons like the
model above to demonstrate where
you’re most likely to find an orbiting
electron. Denser area of the cloud
means higher probability of electrons.
pinpoint their exact locations.
61
Brief History of the Atomic Models
COLOR
JOHN DALTON was the first scientist to propose that elements
SIZE
DENSITY
MALLEABILITY (how easily something
are composed of indestructible atoms. He thought that there
can be flattened, shaped, or pressed)
were particles so small that we could not see them. He called
MAGNETISM (whether or not something is magnetic)
these particles atoms, and his theory on matter was known as
the ATOMIC THEORY OF MATTER.
BOILING POINT and MELTING POINT
(the temperature at which something boils or melts)
SIR JOSEPH JOHN (J. J.) THOMSON discovered
the presence of negatively charged particles
SOLUBILITY (how easily something
(electrons) in atoms and pictured them
dissolves into another substance)
embedded with positively charged particles,
kind of like raisins in oatmeal-raisin cookies.
IS:
HELLO MY NAME
ERN EST
HELLO MY
NAM E IS:
J. J.
A
PHYSICAL CHANGE is any change to the physical properties
of mat ter such as its size, shape, or state (solid, liquid, or
ERNEST RUTHERFORD worked out that atoms had small and
gas/vapor). The final product of any physical change is still
heavy positively charged centers, which he called a nucleus. He
composed of the same matter. For example, you can revert ice,
figured out that electrons were orbiting the nucleus in mostly
snow, or vapor back to water by either heating or cooling them.
empty space. He called the positive particles in the nucleus
Ice, vapor, and water are all H 20-just in different states.
protons. Rutherford’s student SIR JAMES CHADWICK proposed
the existence of uncharged particles in the nucleus, which he
CHEMICAL PROPERTIES describe the ability of something
called neutrons.
to undergo different chemical changes.
PHYSICAL and CHEMICAL
PROPERTIES and CHANGES
The way something looks, feels, smells, and tastes are all
Some examples of chemical properties:
FLAMMABILITY (how easily
something lights on fire)
PHYSICAL PROPERTIES. It's easy to classify matter by these
characteristics. Some common physical properties used to
REACTIVITY (how reactive something
differentiate matter are:
is to oxygen, water, light, etc.)
62
63
1
1
1
H
Hydrogen
1.0078
3
2
3
4
5
6
7
Li
period group
2
4
Be
3
Li
11
12
Sodium
22.990
Ma g nesium
24.305
3
4
5
6
19
20
21
22
23
Potassium
39.098
Calcium
40.078
Scandium
44.956
Titanium
47.867
37
38
39
Rubidium
85.468
Strontium
87.62
Yttrium
88.906
55
56
Caesium
132.91
Barium
137.33
87
Fr
group period
Francium
( 223 )
Lithium
6.941
72
16
17
18
S
Cl Ar
Aluminum
26.982
Silicon
28.084
Phos phorus
30.974
Sulfur
32.059
Chlorine
35.446
Arg on
39.948
34
35
36
Gallium
69.723
Germanium
72.63
Arsenic
74.922
Selenium
78.96
Bromine
79.904
Kr ypton
83.798
45
46
47
48
49
50
51
52
53
Rhodium
102.91
Palladium
106.42
Silver
107.87
Cadmium
112.41
Indium
114.82
Tin
118.71
Antimony
121.76
Tellurium
127.60
I
54
Iodine
126.90
Xe
77
78
79
80
81
82
83
84
85
86
Iridium
1.0078
Platinum
195.08
Gold
196.97
Mercur y
200.59
Thallium
204.38
Lead
207.2
Bismuth
208.98
Polonium
( 209 )
Astatine
( 210 )
Radon
( 222 )
108
109
110
111
112
113
114
115
116
117
118
Bohrium
( 264 )
Hassium
( 269 )
Meitnerium
( 226 )
Ununtrium
( 268 )
Flerovium
( 268 )
60
61
62
Promethium
( 145 )
44
Zirconium
91.224
Niobium
92.906
Moly bdenum
95.96
Technetium
98.9062
Ruthenium
101.07
72
73
74
75
76
Hafnium
178.49
Tantalum
180.95
Tungsten
183.84
Rhenium
186.21
Osmium
190.23
88
104
105
106
107
Radium
( 226 )
Rutherfordium
( 261 )
Dubnium
( 262 )
Seaborg ium
( 266 )
57
58
59
Lanthanum
138.91
Cerium
140.12
89
90
Actinium
( 226 )
Thorium
1.0078
Zr Nb Mo Tc
Ta W Re
Ru
Os
Co
Rh
Ir
92
U
Uranium
238.03
Pd A g Cd In
Pt Au Hg
Tl
Sn Sb
Pb Bi
Se
Te
Br
Kr
Xenon
131.29
Po At Rn
Fl Uup Lv Uus Uuo
Rg Cn Uut
63
64
65
66
67
68
69
70
Samarium
150.36
Euro p ium
151.96
Gadolinium
157.25
Terbium
158.93
Dys p rosium
162.50
Holmium
164.93
Erbium
167.26
Thulium
168.93
Ytterbium
173.04
Lutetium
174.97
93
94
95
96
97
98
99
100
101
102
103
Neptunium
( 237 )
Plutonium
( 244 )
Americium
( 243 )
Curium
( 247 )
Berkelium
( 247 )
Fermium
( 257 )
Mendelevium
( 258 )
Nobelium
( 259 )
Lawrencium
( 262 )
Pr Nd Pm Sm
Praseody mium Neody mium
140.91
144.24
Ni Cu Zn Ga Ge As
Ds
Rf Db S g Bh Hs Mt
Pa
15
Zinc
65.38
43
Protactinium
231.04
14
Co pp er
63.546
42
Ac Th
13
Neon
20.180
Nickel
58.693
Cr Mn Fe
91
Ne
Cobalt
58.933
41
La Ce
F
33
40
Ra
Fluorine
18.998
32
Iron
55.845
Hf
Ox yg en
15.999
31
Man g anese
54.938
Y
Nitrog en
14.006
P
O
10
Carbon
12.009
Si
N
Helium
4.0026
30
Chromium
51.996
V
17
9
29
Vanadium
50.942
Ti
16
8
Boron
10.806
Al
C
15
7
28
24
Ca Sc
B
14
6
He
12
9
27
10
13
5
18
2
11
8
26
Cs Ba
→ NEW AN D PEN DING DISCOVERIES
→ OTHER NONMETALS
7
25
Rb Sr
→ LANTHANIDES
→ ACTINIDES
→ POST-TRANSITION METALS
→ METALLOIDS
Ber y llium
9.0122
K
→ HALOGENS
→ NOBLE GASES
→ TRANSITION METALS
→ UNKNOWN PROPERTIES
Lithium
6.941
Na M g
→ ALKALAI METALS
→ ALKALINE EARTH METALS
Np Pu
Darmstadtium Roentg enium Co p ernicium
( 268 )
( 268 )
( 268 )
Unun p entium Livermorium Ununseptium
( 268 )
( 268 )
( 268 )
Eu Gd Tb Dy Ho Er Tm Yb
Am Cm Bk
Cf
Californium
( 251 )
Es
Einsteinium
( 252 )
Ununoctium
( 268 )
71
Lu
Fm Md No Lr
73
solution
There are two kinds of mixtures:
a homogenous mixture
1. Heterogeneous mixture: a mixture where the
substances aren’t evenly mixed. A salad is an example
of a heterogeneous mixture; every bite of a salad is
different no matter how many times you mix the salad.
HETERO is Greek for “ different,” so the mixture
has different parts; it’s not all the same.
2. Homogenous mixture: a mixture where the molecules
of each substance are equally mixed, and you can’t see
the different parts of the mixture. Sugar that has been
dissolved in water creates a homogenous mixture; you
can’t see the sugar and the water, just a liquid that
contains molecules of both.
HOMO is Greek for “same,” so the
mixture is the same throu g hout.
solvent
the substance into which
the solute dissolves
SOLUTIONS. A solution
is made of a SOLUTE and a
SOLVENT. A solute is the substance
SOLUBILITY is the ability of a substance to dissolve into
another substance. Lots of things affect solubility:
Temperature
is one factor:
Usually solid solutes are
more soluble in water at
higher temperatures, which
is why it is easier to
dissolve sugar in
hot water.
SOLUTE
SOLV ENT
that gets dissolved, and the solvent
is the substance that dissolves the
solute. For example, some sports drinks are a solution that is
made of water and powdered sports drink mix.
84
the substance that
is dissolved into the
other substance
SOLUBILITY
Sometimes homogenous mixtures
are called
solute
PRESSURE
and the
CONCENTRATION
of other solvents in a
solution also affect
solubility.
Gases can
be dissolved
into liq uid,
too!
Gas solutes,
like carbonation,
are the opposite. Gases
are more soluble in liquids at
colder temperatures. Carbonated
beverages remain fizzy longer
when they are cold because
gas is more soluble
in cold liquid.
85
Electrical Circuit
Batteries
An electric current will continuously flow if the charges can
Bat teries provide the energy source that pushes the electric
travel in a closed conducting loop, called a CIRCUIT. The
charges around a circuit. When connected to a circuit,
electric field keeps the charge moving.
a bat tery creates an electric field with a positive and
negative terminal at each end of the bat tery (which is
The components of a circuit are:
electrical conductor,
such as a wire, connects to the
power source to form a closed
loop (a connection with no
openings or breaks)
load (not necessary,
but usually there), a
device that the circuit
is powering, like a
lightbulb, fan, or
speaker.
the
+ or - sign you see on different sides of the bat tery).
The electrons, which are the moving charges in a current,
are at tracted to the positive terminal and repelled by the
negative terminal. They travel like traffic on a road (as long
as the circuit is a closed loop).
Voltage
The energy of flowing electrons
in a circuit is called
VOLTAGE.
Voltage, measured in volts (V), is
voltage
the amount of potential
energy an electron in a
circuit can gain
the electric potential difference
between two points in a circuit, such as the positive and
negative terminals of a battery. Voltage provides potential
energy to an electron, just like gravity provides potential
energy to a ball held above the ground The higher the voltage,
the greater the potential difference, and the more energy
power source
of electrical energy,
such as a battery
the current can supply. So a 9-volt battery will make a small
switch (not necessary,
but frequently there) is a device
to open and close a circuit
lightbulb glow much brighter than a AA battery would (which
is 1.5 volts).
IT’S LIKE A DRAWBRID G E ON A ROAD.
164
165