Download Chapter 4

Chapter 3&4
4 types of matter
Solid to liquid - MELTING
Liquid to gas - VAPORIZATION
Gas to liquid - CONDENSATION
Liquid to solid - FREEZING
Solid to gas – SUBLIMATION
Gas to solid – DEPOSITION
CHAPTER 4
- Atomic theory - originally, they thought
that everything was made up of 4
things….Earth, Wind, Fire, & Water.
- They were wrong!
- Democritus – ancient Greek philosopher;
who came up with the concept of the
atom. He said that everything was made
up of extremely small particles that could
not be cut into anything smaller.
Dalton’s Atomic Theory
1. All elements are made of atoms that can
not be divided.
2. All atoms of the same element are
EXACTLY alike and have the same
mass.
3. Atoms of one element CAN NOT
change into another type of element. In
a chemical reaction, they can not be
created or destroyed, only rearranged.
4. Every compound is made of atoms of
different elements combined in specific
ways.
JJ Thomson – discovered electron using
cathode ray tube experiment
Rutherford – discovered nucleus using gold
foil experiment
Neils Bohr – made first accurate model of
atom using a nucleus with electrons spinning
around outside
3 parts of an atom
ATOMIC NUMBER
Atomic # never changes.
Mass Number
Symbol is A
Total number of protons and neutrons in an
atom.
Called mass number because, when we find
the weight (mass) of an atom, we use both
the protons and the neutrons.
Isotopes
Atoms with the same number
of protons and a different
number of neutrons are called
isotopes.
An isotope is identified by its
mass number, which is the
sum of the protons and
neutrons in the nucleus of the
atom.
Example: Carbon has three isotopes
Carbon-12 has 6 protons and 6 neutrons
Carbon-13 has 6 protons and 7 neutrons
Carbon-14 has 6 protons and 8 neutrons
IONS
Ion – an electrically charged atom
2 types
(+) ion is a cation - positive
(- ) ion is an anion - negative
Isotopic Symbol
Calculating Molecular Mass
To find the weight of a molecule, you must
do the following steps.
1. write down the molecular formula
2. find the number of each type of atom
3. multiply the coefficient of each atom by
the atomic wt. (on periodic table)
4. add them together
Chapter 4.2
Mendeleev created the periodic table!!!!!
He set it up in patterns. He predicted that
some elements had not been discovered yet
and left space for them on the table.
No one believed him, until the elements
were discovered and had the characteristics
he said they would have.
He set it up according to increasing atomic
mass. Today it is by atomic number.
Periodic Table
Period – horizontal row (across)
G
R
O
U
P
- vertical row (up and down)
Group 1A – Alkali Metals, +1 charge
Group 2A – Alkaline Earth Metals +2 charge
Group 6A – Chalcogens, -2 charge
Group 7A – Halogens, -1 charge
Group 8A – Noble Gases, NO charge
How to read an element square on the
periodic table
Each periodic table has the same basic
features, but things are not always in the
same place.
Atomic mass – this is the average mass of an
atom (remember that because of isotopes, not
all atoms of the same element have the same
weight because of the neutrons). Measured
in AMU or atomic mass units.
How Elements Form
Elements form in the stars. Kind of like the
big bang.
Stars are formed of Hydrogen plasma. It is
super-heated H gas. The electrons in plasma
do not spin around the nucleus of the atoms.
They float everywhere. This leaves the H
nuclei free to bounce into other H nuclei,
forming new elements. Nuclear FUSION.
4.3 Metals
Properties of metals
1. conduct electricity & heat
2. shiny
3. malleable – you can bend it and
shape it with a hammer, flatten it
4. ductile – you can stretch it out into
wires
5. Reactivity – how easily it will get
into a chemical reaction. Most
metals will react easily. They lose
electrons and turn into CATIONS.
-
Alkali Metals – Group 1
Highly reactive (explosive reactions).
Li, Na, K, Rb, Cs, Fr
Cations +1 charge
Not found alone in nature, they are
always found in a compound
Alkaline Earth Metals – Group 2
- reactive, but not as much as alkali metals
- Be, Mg, Ca, Sr, Ba, Ra
- Cations +2
-
Transitions Metals
the middle block in the periodic table
All of them are metals
All of them are cations, but their charges
vary
Not as reactive as group I or II. Used in
jewelry, coins, wires.
Conduct electricity
Metals in Mixed Groups
- found just below the metalloids in groups
3A, 4A, 5A
- very unreactive.
- Al is a good example. Used in soda cans
because it does not react with the soda.
Synthetic elements
- Man-made elements. They do not last but
a few seconds in a lab.
- The correct way to name them now is to
use pre-fix symbols instead of fighting
over a name. Bbp would be 225, Uns
107
4.4
Nonmetals
- poor conductors of heat and electricity
- dull
- brittle (break/shatter when hit with a
hammer)
- form ANIONS
- found on right side of periodic table
- most are gases (10 out of 16)
Carbon Group – 14
- can gain or lose 4 electrons
- only carbon is a nonmetal, all others
are metalloids or mixed group metals
- carbon is a fossil fuel
Nitrogen Group – 15
- 2 nonmetals, Nitrogen and Phosphorus
- Anion (-3)
- Air is 80% N2 gas
- N and P are fertilizers
Chalcogen Group – 16
- Oxygen group
- Anion (-2)
- O, S, Se are nonmetals
- O2 gas is what we breathe
- O is the most abundant element in the
earth’s crust and the 2nd most abundant
element in the air.
- O is highly reactive
- S is a solid, yellow in color and smells
like rotten eggs
Halogens – 17
- highly reactive nonmetals
- anion (-1)
- deadly gases
- halogens form SALTS when combined
with other elements (NaCl)
- Br is a liquid at room temperature
Noble Gases – 18
- do not combine with any other element
- do NOT form ions because they have
8 electrons in their outermost shell.
- Will not react
- All of them are gases
Hydrogen –
- special element, all by itself.
- Nonmetal
- CATION +1
- Extremely reactive
METALLOIDS
- Characteristics of both metals and
nonmetals. ½ of each
- All are solids
- 8 metalloids
- Found between metals and nonmetals
on periodic table
- MOST IMPORTANT FACTOR!!!
Metalloids conduct electricity partially;
this means that they are used in ALL
electronic devices!!! Silicon chips
called semiconductors
Diatomic Elements
There are 7 elements that ALWAYS
combine with themselves. They are
NEVER found alone. Memorize these
Moles to Mass & Avogadro’s Number
A mole is defined as the number of
atoms in exactly 12 grams of carbon-12.
The mole is the SI unit for the amount
of a substance.
Chemists use the mole as a counting
unit—for example you use a dozen as a
counting unit for 12.
To convert between moles and grams,
chemists use the molar mass of
substance.
Molar mass has the unit grams/mole
(g/mol)
The mass in grams of 1 mol of an
element is numerically equal to the
element’s atomic mass from the periodic
table in atomic mass units.
For example, the atomic mass of copper
to two decimal places is 63.55 amu.
Therefore, the molar mass is
63.55 g/mol.
Scientists have also determined the
number of particles in 1 mole of a
substance, called Avogadro’s number.
One mole of a pure substance contains
6.0221367 x 1023 particles.
Avogadro’s number will be rounded to
6.022 x 1023 particles per mol.
Converting moles to mass
Determine the mass in grams of 3.50
mol of copper.
4.5
Radioactivity
Marie Curie came up with the name
radioactivity
Radioactivity means that an atom is
unstable. It loses small energy bursts
from its nucleus (creating radiation that
is harmful).
Alpha particle – is when 2 protons and 2
neutrons escape an atom – can be
stopped by paper
Beta particle – fast moving electron that
is released from an atom – stopped by
aluminum
Gamma Rays – high energy waves that
are emitted by an atom when it breaks
apart. DEADLY
Uses of Radioactive Isotopes
1. tracing the steps of chemical
reactions
2. nuclear power plants
3. industrial processes
4. treating disease
Tracers are radioactive isotopes that can
be followed through the steps of a
chemical reaction or industrial process.
Doctors use radioactive isotopes to detect
medical problems and to treat some
diseases.
In a process called radiation therapy,
radioactive elements are used to destroy
unhealthy cells.
Cancer cells of different kinds often are
treated from outside the body with highenergy gamma rays.