Download Physical Science EOCT Review Domain 1: Chemistry

Physical Science EOCT Review
Domain 1: ChemistryAtomic and Nuclear Theory
and the Periodic Table
Domain 1: ChemistryAtomic Theory
Dalton’s Atomic Theory (experiment based)
John Dalton
(1766 – 1844)
1) All elements are composed of
tiny indivisible particles called
atoms
2) Atoms of the same element are
identical. Atoms of any one
element are different from
those of any other element.
3) Atoms of different elements combine in
simple whole-number ratios to form
chemical compounds
4) In chemical reactions, atoms are combined,
separated, or rearranged – but never
changed into atoms of another element.
Sizing up the Atom
Elements are able to be subdivided into
smaller and smaller particles – these are
the atoms, and they still have properties
of that element
If you could line up 100,000,000
copper atoms in a single file, they
would be approximately 1 cm long
Despite their small size, individual
atoms are observable with instruments
such as scanning tunneling
microscopes
Subatomic Particles
Particle
Charge
Mass (g)
Location
Electron
(e-)
-1
9.11 x 10-28
Electron
cloud
Proton
(p+)
+1
1.67 x 10-24
Nucleus
Neutron
(no)
0
1.67 x 10-24
Nucleus
The Rutherford Atomic Model
• Based on his experimental evidence:
–The atom is mostly empty space
–All the positive charge, and almost all
the mass is concentrated in a small area
in the center. He called this a “nucleus”
–The nucleus is composed of protons
and neutrons
–The electrons distributed around the
nucleus, and occupy most of the volume
–His model was called a “nuclear model”
Atomic Number
• Atoms are composed of protons,
neutrons, and electrons
– How then are atoms of one element
different from another element?
• Elements are different because they
contain different numbers of PROTONS
• The “atomic number” of an element is
the number of protons in the nucleus
• # protons in an atom = # electrons
Atomic Number
Atomic number (Z) of an element is
the number of protons in the nucleus
of each atom of that element.
Element
# of protons
Atomic # (Z)
Carbon
6
6
Phosphorus
15
15
Gold
79
79
Mass Number
Mass number is the number of
protons and neutrons in the nucleus
of an isotope: Mass # = p+ + n0
Nuclide
Oxygen - 18
Arsenic
- 75
Phosphorus - 31
p+
n0
e- Mass #
8
10
8
18
33
42
33
75
15
16
15
31
Symbols
Find each of these:
a) number of protons
b) number of
neutrons
c) number of
electrons
d) Atomic number
e) Mass Number
80
35
Br
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.
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.
Atomic Mass
How heavy is an atom of oxygen?
It depends, because there are different
kinds of oxygen atoms.
We are more concerned with the average
atomic mass.
This is based on the abundance
(percentage) of each variety of that
element in nature.
We don’t use grams for this mass because
the numbers would be too small.
Measuring Atomic Mass
• Instead of grams, the unit we use
is the Atomic Mass Unit (amu)
• It is defined as one-twelfth the
mass of a carbon-12 atom.
– Carbon-12 chosen because of its isotope purity.
• Each isotope has its own atomic
mass, thus we determine the
average from percent abundance.
To calculate the average:
• Multiply the atomic mass of
each isotope by it’s
abundance (expressed as a
decimal), then add the
results.
• If not told otherwise, the mass of the
isotope is expressed in atomic mass
units (amu)
Atomic Masses
Atomic mass is the average of all the
naturally occurring isotopes of that element.
Isotope
Symbol
Carbon-12
12C
Carbon-13
13C
Carbon-14
14C
Composition of
the nucleus
6 protons
6 neutrons
6 protons
7 neutrons
6 protons
8 neutrons
Carbon = 12.011
% in nature
98.89%
1.11%
<0.01%
The Periodic Table:
A Preview
A “periodic table” is an
arrangement of elements in which
the elements are separated into
groups based on a set of repeating
properties
The periodic table allows you to
easily compare the properties of
one element to another
The Periodic Table:
A Preview
Each horizontal row (there are 7 of
them) is called a period
Each vertical column is called a
group, or family
Elements in a group have similar
chemical and physical properties
Identified with a number and
either an “A” or “B”
More presented in Chapter 6
Domain 1: ChemistryRadioactivity and Nuclear
Chemistry
Types of Radioactive Decay
• Alpha Decay (α)
– Alpha particles are just helium nuclei.
– Mass number = 4 (4 amu)
– Charge = 2+
– Low penetration power (Paper & clothing stop
them.)
• Beta Decay (β)
–Beta particles are just electrons.
–Mass number = 0 (1/1837 amu)
–Charge = -1
–Medium penetration power (Metal
foil stops them).
• Gamma Decay (γ)
– Gamma radiation is high energy
electromagnetic radiation.
– Mass number = 0
– Charge = 0
– High penetration power (Thick lead shield
stops them.)
Radioactive Decay of a
Hypothetical 31P Sample
• Simulating Radioactive Decay
– You just won $1,000, but…
– …you can only spend half of it
in month 1…
– …half of the remainder in month
2, etc.
– After how many months would
you be left with less than $1?
– What is the half life for this
prize?
Common Half-Lives &
Radiation*
ISOTOPE
Carbon-14
Potassium-40
Radon-222
Radium-226
Thorium-230
Thorium-234
Uranium-235
Uranium-238
HALF-LIFE
5,730 years
1,25 X 109 years
3.8 days
1,600 years
75,400 years
24.1 days
7.0 X 108 years
4.46 X 109 years
RADIATION
Beta
Beta, gamma
Alpha
Alpha, gamma
Alpha, gamma
Beta, gamma
Alpha, gamma
Alpha
Radiocarbon Dating
• In the upper atmosphere 14C forms
at a constant rate:
14
7N
14
6C
→
+ 01 n →
14
7N
+
0
-1 β
14
6C
+ 11 H
T½ = 5730 Years
• Live organisms maintain 14C/13C at
equilibrium.
• Upon death, no more 14C is taken up
and ratio changes.
• Measure ratio and determine time since
death.
Nuclear Fission
The atom has been split.
Fission
• splitting a nucleus into two or more
smaller nuclei
• 1 g of 235U =
3 tons of coal
235
92
U
Fission
• Nuclear chain reaction self-propagating
reaction, a continuous
series of nuclear fission
reactions.
• critical mass the minimum amount of
a substance than can
undergo a fission
reaction and can sustain
a chain reaction.
Nuclear Fusion
• Fusion produces the energy of the
sun.
• Most promising process on earth
would be:
4
3
1
2
1H
+ 1H
→
2 He
+ 0n
• Plasma temperatures over
40,000,000 K to initiate a selfsustaining reaction (we can’t do
this yet).
Fusion
• combining of two nuclei to form one
nucleus of larger mass
• thermonuclear reaction – requires
temp of 40,000,000 K to sustain
• 1 g of fusion fuel =
20 tons of coal
• occurs naturally in
stars
2
1
3
1
H+ H
Applications of Nuclear
Reactions
• Dating of ancient artifacts (Carbon-14).
• Smoke detectors (Americium-241).
• Radioactive tracers in medicine (Iodine131, barium-140, phosphorus-32).
• Cancer treatment (Cobalt-60).
More Applications of Nuclear
Reactions
• Electricity generation (Uranium-235).
• Artificial (lab-made) elements (beyond Z =
92).
• Bombs (Uranium-235).
• Fusion (Combining two small nuclei to
form a large nucleus.)
• Interested in learning more?.
Radioactive Waste Disposal
• Low level waste.
–Gloves, protective clothing,
waste solutions.
• Short half lives.
• After 300 years these materials
will no longer be radioactive.
Radioactive Waste Disposal cont.
• High level waste.
–Long half lives.
• Pu, 24,000 years and extremely
toxic.
• Reprocessing is possible but
hazardous.
–Recovered Pu is of weapons
grade.
Domain 1: ChemistryPeriodic Table
Mendeleev’s Periodic Table
• By the mid-1800s, about 70
elements were known to exist
• Dmitri Mendeleev – Russian
chemist
• Arranged elements in order of
increasing atomic mass
• Thus, the first “Periodic Table”
Mendeleev
• Left blanks for
undiscovered elements
–When they were discovered, he
had made good predictions
• But, there were problems:
–Co and Ni; Ar and K; Te and I
A better arrangement
• In 1913, Henry Moseley –
British physicist, arranged
elements according to
increasing atomic number
• The arrangement used today
• The symbol, atomic number
& mass are basic items
included
The Periodic Law says:
• When elements are arranged in
order of increasing atomic
number, there is a periodic
repetition of their physical and
chemical properties.
• Horizontal rows = periods
– There are 7 periods
• Vertical column = group (or family)
– Similar physical & chemical prop.
– Identified by number & letter
Electron Configurations in Groups
1) Noble gases are the elements
in Group 8A
•
•
Previously called “inert gases”
because they rarely take part in a
reaction
Noble gases have an electron
configuration that has the outer s and
p sublevels completely full
Electron Configurations in Groups
2) Representative Elements are
in Groups 1A through 7A
•
•
•
Display wide range of properties, thus
a good “representative”
Some are metals, or nonmetals, or
metalloids; some are solid, others are
gases or liquids
Their outer s and p electron
configurations are NOT filled
• Elements in the 1A-7A groups
8A
1A
are called the representative
2A elements
3A 4A 5A 6A 7A
outer s or p filling
Valence Electrons in
Representative groups
•
•
•
•
•
•
•
•
1A
2A
3A
4A
5A
6A
7A
8A
1 valence electron
2 valence electrons
3 valence electrons
4 valence electrons
5 valence electrons
6 valence electrons
7 valence electrons
8 valence electrons
except He with 2 valence
electrons
12
Helium only has 2
valence electrons
8
3 4 5 67
Memorize this rhyme.
• “1+, 2+, 3+, skip, 3-, 2-, 1-, zip”
• This tells you the Ionic charge and
oxidation numbers for the elements in the
8 REPRESENTATIVE GROUPS, 1A-8A,
as you count form left to right.
Ions
• Some compounds are composed
of particles called “ions”
– An ion is an atom (or group of atoms) that
has a positive or negative charge
– Atoms are neutral because the number of
protons equals electrons
– Positive and negative ions are formed when
electrons are transferred (lost or gained)
between atoms
Ions
• Metals tend to LOSE electrons,
from their outer energy level
– Sodium loses one: there are now more
protons (11) than electrons (10), and
thus a positively charged particle is
formed = “cation”
– The charge is written as a number
followed by a plus sign: Na1+
– Now named a “sodium ion”
Ions
• Nonmetals tend to GAIN one or
more electrons
– Chlorine will gain one electron
– Protons (17) no longer equals the
electrons (18), so a charge of -1
– Cl1- is re-named a “chloride ion”
– Negative ions are called “anions”
Areas of the periodic table
• Three classes of elements are:
1) metals, 2) nonmetals, and
3) metalloids
1) Metals: electrical conductors, have
luster, ductile, malleable
2) Nonmetals: gererally brittle and
nonlustrous, poor conductors of
heat and electricity
Metals
Metals
•
•
•
•
Luster – shiny.
Ductile – drawn into wires.
Malleable – hammered into sheets.
Conductors of heat and electricity.
Non-metals
• Dull
• Brittle
• Nonconductors
- insulators
Areas of the periodic table
• Some nonmetals are gases (O,
N, Cl); some are brittle solids
(S); one is a fuming dark red
liquid (Br)
• Notice the heavy, stair-step
line?
3) Metalloids: border the line
– Properties are intermediate between
metals and nonmetals
Metalloids or Semimetals
• Properties of both metals and
nonmetals
• Semiconductors
#1. Atomic Size - Group trends
• As we increase the
atomic number (or
go down a group). .
.
• each atom has
another energy
level,
• so the atoms get
bigger.
H
Li
Na
K
Rb
#1. Atomic Size - Period Trends
• Going from left to right across a period, the
size gets smaller.
• Electrons are in the same energy level.
• But, there is more nuclear charge.
• Outermost electrons are pulled closer.
Na
Mg
Al
Si
P
S Cl Ar
Atomic size and Ionic size increase
in these directions:
#2. Trends in Electronegativity
• Electronegativity is the tendency for
an atom to attract electrons to itself
when it is chemically combined with
another element.
• They share the electron, but how
equally do they share it?
• An element with a big
electronegativity means it pulls the
electron towards itself strongly!
Electronegativity Group Trend
• The further down a group,
the farther the electron is
away from the nucleus, plus
the more electrons an atom
has.
• Thus, more willing to share.
• Low electronegativity.
Electronegativity Period Trend
•
•
•
•
Metals are at the left of the table.
They let their electrons go easily
Thus, low electronegativity
At the right end are the nonmetals.
• They want more electrons.
• Try to take them away from others
• High electronegativity.
The arrows indicate the trend:
Ionization energy and Electronegativity
INCREASE in these directions
Domain 1: ChemistryPhases of Matter
Kinetic Theory
• Kinetic means motion
• Three main parts of the theory
– All matter is made of tiny particles
– These particles are in constant motion and
the higher the temperature, the faster they
move
– At the same temperature, heavier particles
move slower.
States of Matter
•
•
•
•
•
•
Solid
Particles are tightly packed
Stuck to each other in a pattern
Vibrate in place
Can’t flow
Constant volume
States of Matter
•
•
•
•
•
Liquid
Particles are tightly packed
Able to slide past each other
Can flow
Constant volume
States of Matter
•
•
•
•
•
Gas
Particles are spread out
Flying all over the place
Can flow
Volume of whatever
container their in
#1. Boyle’s Law - 1662
Gas pressure is inversely proportional to the
volume, when temperature is held constant.
Pressure x Volume = a constant
Equation: P1V1 = P2V2 (T = constant)
• The combined gas law contains
all the other gas laws!
• If the temperature remains
constant...
P1 x V1
T1
=
P2 x V2
T2
Boyle’s Law
#2. Charles’s Law - 1787
The volume of a fixed mass of gas is
directly proportional to the Kelvin
temperature, when pressure is held
constant.
This extrapolates to zero volume at a
temperature of zero Kelvin.
V1
V2
=
T1
T2
( P = constant)
• The combined gas law contains
all the other gas laws!
• If the pressure remains
constant...
P1 x V1
T1
=
P2 x V2
T2
Charles’s Law
#3. Gay Lussac’s Law 1802
•The pressure and Kelvin temperature of
a gas are directly proportional, provided
that the volume remains constant.
P1 P2
=
T1 T2
•How does a pressure cooker affect the time
needed to cook food?
•Sample Problem 14.3, page 423
The
combined gas law contains
all the other gas laws!
If the volume remains
constant...
P1 x V1
T1
=
P2 x V2
T2
Gay-Lussac’s Law
#4. The Combined Gas Law
The combined gas law expresses the
relationship between pressure, volume
and temperature of a fixed amount of
gas.
P1V1 P2V2
=
T1
T2
Sample Problem 14.4, page 424