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Chemistry
Matter and Classification
Purpose of classification: To gain a better understanding and
appreciate the similarities and differences.
Matter: Has mass and occupies space.
We can divide matter into 2 categories:
Matter
Mixtures
Pure Substances
Heterogeneous
Elements
Metals
Nonmetals
Alloy
Compounds
Ionic
Molecular
Homogeneous
Solutions
Pure Substances
Substances that are the same or consistent throughout.
Can be a single element or a combination of elements.
Elements
Substance composed of only one kind of atom. 109 on the periodic table. Each
has a unique international symbol. Can be combined to make other pure
substances.
Compounds
Combination of two or more elements in specific proportions. Once combined the
compound acts as one, with consistent chemical and physical properties.
Mixtures
A combination of two or more compounds.
Homogeneous
A mixture in which all regions are consistent (the same)
Ex. Sugar water (a solution)
brass (an alloy - mixture of 2 metals; copper and zinc)
air (gas solution)
Heterogeneous
A mixture that can be easily separated, not consistent. Regions of differing properties.
Ex. Sand and water.
Chemical vs Physical Properties
Chemical
Describes the reactivity of a substance
Physical
Properties that describe the appearance or the composition of a
substance. In a physical change no new substance is being
formed.
Chemical Reactions
The process that occurs when a substance or
substances reacts to create a different
substance
Indicators of a Chemical Reactions
1. Involve the production of a new substance
2. Involve the flow of energy (exothermic and endothermic)
Exothermic - Release of energy in the form of heat, light,
sound etc
ex. Cellular Respiration, combustion
DEMO
Endothermic - Absorption of energy (It cools, uses light etc.)
ex. Photosynthesis, Ba(OH)2(s) + NH4SCN(s) DEMO
3. Involve the formation of a gas
ex. Hydrogen gas formation when Mg(s) is placed in HCl(aq)
DEMO
4. Involves the formation of a solid in a liquid (precipitate)
ex. KI(aq) + PbNO3(aq) DEMO
Read Pages 12 to 17 and answer the following
questions:
Pg 17 #1 to 9
The Development of an Atomic Model
As theories developed old ideas were not discarded, they were modified and
expanded upon.
Democritus 460BC
Democritus develops the idea of atoms
he pounded up materials in his pestle
and mortar until he had reduced
them to smaller and smaller particles
which he called
ATOMA
(greek for indivisible)
1808
John Dalton - Billiard Ball Model
Atom is in the shape of a billiard
ball and acts as a single,
indestructible and indivisible
particle. The larger the atomic
number the larger the atom or
“billiard ball”
Observations that supported this theory:
Law of Conservation of mass: The masses of the
reactants always equals the masses of the products.
Example: 2 g of hydrogen and 16 g of oxygen
would react to produce 18 g of water.
J.J Thomson "Raisin Bun" Model
Atoms have negatively charged
particles embedded in them like
raisins in a bun.
Observations that supported theory:
-electricity passed through a gas in a
vacuum tube produced a stream of
negatively charged particles.
Rutherford
“Nuclear” Model
An atom’s mass is concentrated in a
very small,dense and positively
charged nucleus. Electrons orbit the
nucleus at a distance.
Observations that supported theory:
Gold foil experiment- large positively
charged particles should go right
through the gold foil. Most did but
some came right back towards the
particle emitter.
Bohr
“Orbits” Model
Electrons are located in specific orbits, each having a specific
energy level, around the nucleus. It is the electrons in the
outermost orbit that react with neighboring atoms to form
compounds.
Observations that supported theory:
electricity passed through a gaseous element emits only certain
wavelengths of light.
Quantum Mechanical Model “Electron Cloud Model”
Electrons are in a cloud moving very quickly around a nucleus forming an
electron cloud.
Read pages 18 to 25 and answer
the following questions:
Pg 25: #1 to 8, 10 and 11.
2. Metals vs Non-metals
separated by the staircase line
Staircase line
Metals
Non-metals
3. Groups (or families)
vertical columns that have similar properties
4. Periods
Horizontal rows with repeated trends of reactivity.
Example:
Calcium
Atomic Number: _____
metal/nonmetal: _____
group:
period:
_____
_____
The periodic table can also list the physical
state (phase) of the element at SATP (room
temperature).
Regular Print - Solid
Clear Print - Gas
Bold - liquid (There are only 2, Mercury and Bromine)
Other physical properties such as electronegativity and molar
mass can also be determined by using the key on your periodic
table.
Families of the Periodic Table
Group IA: Alkali Metals
Elements are highly reactive.
Contain most reactive metal: Francium.
Silver colored
Very ductile
React with air or water
As you move from top to bottom they become more reactive
Group II A: Alkaline Earth Metals
Similar to alkalies but not as reactive in air.
Oxidize with air to form a protective coating
When mixed in solution are likely to form a compound with a pH greater than 7.
Group VIIA or 17: Halogens - “Salt Formers”
Reacts well with metals to form compounds similar to salts.
Most diverse Group. Contains all phases.
Contains most reactive non-metal: Fluorine
As you move up the column they become more reactive.
Group VIIIA or 18: Noble Gases.
Seldom reacts to form compounds.
formerly called the “Inert Gases”
Group B elements: Transition Metals
typical metals such as copper, iron, zinc and silver
wide variety of characteristics
Metal Non-Metal Staircase:
Metal vs Non-Metal Properties
Metals
Non-Metals
-solid (except Hg)
-s, l, g
-silver(except: copper, gold)
-all colors
-ductile & malleable
-brittle/inflexible
-conduct heat/electricity
-poor conductors of
heat and electricity
-reacts with acid to form
hydrogen gas
Metalloids
Nonmetals along the staircase line that have some of the
properties of metals, mainly they can conduct electricity.
(semiconductors)
Lanthanides and Actinides
Last Two Groups - found at the bottom of the periodic table
Rare Earths / Lanthanide Series: Name says it all, atomic #’s 58 - 71
Trans Uranium /Actinide Series: Made in nuclear reactors, #’s 90-103
Atom
Atomic Structure
The basic unit of matter. Smallest unit of matter that retains the
properties of the element. Consists of subatomic particles.
Subatomic Particles
1. Proton: symbol “p+”
-Positively charged particle located in the center of an atom
(nucleus). Makes up a large portion of the mass of an atom.
2. Neutron: symbol “n°”
-Neutral charged particle located in the center of the atom
(nucleus). Also makes up a large portion of the mass of the atom
***Atomic mass of any element is determined by the number of
protons and neutrons.
3. Electron: symbol “e-”
-Negatively charged particle surrounding an atom.
-Has very little mass. Moves about the nucleus in an electron
cloud. Cloud consists of mostly space.
If the nucleus was the size of a ping pong ball the first electron
would be about 0.5 km away!
Finding Numbers of Subatomic Particles
Protons = Atomic Number
*Proton number can never, never, never change.
Electrons = Atomic Number (neutral atom only!) *Electron number
can change if an ion.
Neutrons = Mass number - Atomic number.
Isotopes: Atoms that have a different number of neutrons from
another atom of the same element.
U 235 is a light isotope having 3 fewer neutrons than the most
common form of uranium
U 239 is a heavy isotope having 1 more neutron than the most
common form of uranium
Periodic Table
Elements on the periodic table are classified and arranged according to four basic patterns.
1. Atomic Number
the number of protons (positively charged particle) in the nucleus of an element.