Chapter 16- Elements of Chemistry
Big Idea: **
Each atom has a sort of stickiness that enables it to connect to other atoms
These groups of atoms are called **
Example:
1. Two atoms of hydrogen chemically combined with one atom of
oxygen becomes water
2. Two atoms of hydrogen chemically combined with two atoms of
oxygen becomes hydrogen peroxide- a disinfectant
16.1 Chemistry: the Central Science
Chemistry – def. – **
Chemistry is considered the central science because it touches all other sciences.
It springs from the principles of **
Serves as a foundation for the most complex science- **
It is also important as a backbone of **
Basic research- **
Applied research- **
16-2 The Submicroscopic World
Atoms are so small that a single grain of sand contains about 125 million trillion of them
Some atoms link together to form larger but still incredibly small basic units of matter called **
Example: water – H2O – two atoms of hydrogen chemically combined with one atom of oxygen
An 8-oz glass of water contains a trillion trillion water molecules
Levels of magnification
Macroscopic – matter large enough to be seen, measured and handled
Microscopic- matter that is so fine that it can only be seen with a microscope
Submicroscopic- the realm of atoms and molecules
Phases of Matter
Matter on this planet can exist in three phases- **
At the submicroscopic level, solid, liquid, and gaseous phases are distinguished by how the
submicroscopic particles hold together.
Solids
Solid phase- **
Solids have definite volume and definite shape
Liquids
Liquid phase- **
Liquids have definite volume but no definite shape.
Gases
Gas phase- **
Gases have no definite volume and no definite shape
Applying pressure to a gas squeezes the gas particles closer together, which decreases the
volume.
16.3 Change of Phase
In order to change the phase of a substance, you must either **
Melting – **
Freezing- **
Evaporating (evaporation)-**
Condensing (condensation)- **
Subliming (sublimation)- **
The underlying cause of phase changes is always the **
Heat of fusion- **
For water, this is 334 J/g
Heat of vaporization- **
For water, this is 2256 J/g- this is why you can briefly touch a wetted finger to a hot stove
without harm
16.4 Physical and Chemical Properties
Physical PropertiesDefinition- **
Chemical PropertiesDefinition- **
Physical Properties
Physical Properties of a substance can change when conditions change without changing its chemical
identity
Cooling liquid water to below 00 C causes the water to change to solid ice. But it is still water,
no matter what phase it is in. The only thing that changes is how the H2O molecules are
arranged. This is an example of a physical change.
Physical change
Definition- **
These can be things like change in size, density, phase, etc.
IMPORTANT NOTE: PHASE CHANGES ARE ALWAYS PHYSICAL CHANGES.
Chemical Properties
Definition- **
Examples:
1. Methane gas has a chemical property of reacting with oxygen to produce carbon dioxide
and water along with appreciable heat. (how many heat their homes)
2. Copper has a chemical property of reacting with carbon dioxide and water to produce a
new greenish-blue solid known a patina. (why copper statues turn green)
3.Gold does not react with acid but iron does.
Chemical Change
During a chemical change, there is a change in the way the atoms are chemically bonded to
one another
A ** is the force of attraction between two atoms that holds them together
So a chemical change is any change in a substance that involves a rearrangement of the way
the atoms are bonded
Chemical Reaction
We call chemical changes- reactions
So a chemical change means the same thing as a chemical reaction
During a chemical reaction, new materials are formed by a change in the way atoms are
bonded together.
16.5 Determining Physical and Chemical Changes
After a**, the molecules are the same ones you started with.
Water vapor (gas) is still H2O even after the liquid water has boiled into the vapor.
After a **, the original molecules have been taken apart and new molecules are in their place.
Chemically reacting iron with oxygen makes a new substance – rust which is reddish brown
instead of silver.
How to tell if a chemcial or physical reaction has taken place
Guidelines:
In a physical change, a change of appearance is the result of a new set of conditions imposed
on the same material. Restoring the original conditions restores the original appearance
Frozen water melts on warming
In a chemical change, a change in appearance is the result of the formation of a new material
that has its own unique set of physical properties. Look for evidence of different properties
Iron is a material used to build cars. Rust is not.
16.6 the Periodic Table
The ** is a listing of all the known elements with their atomic masses, atomic numbers
and
atomic symbols.
Most of the known elements are metals
Metals are elements that are shiny, opaque and good conductors of heat and electricity
Metals are malleable, which means they can be hammered into different shapes or bent
without breaking
Metals are ductile, which means they can be drawn into wires.
More on metals
All but a few metals are solid at room temperature
Exceptions: Mercury (Hg) is a liquid at 250 C (770 F)
Gallium (Ga), Cesium (Cs) and Francium (Fr) will become liquids at 300 C (860 F)
Another notable exception: Hydrogen (H) which normally behaves like a nonmetallic gas will
take on the properties of a liquid metal at very high pressures
Metals can be found to the left of the zigzag line and takes up 2/3 of the periodic table
Nonmetals
Located at the far right side of the periodic table (with the exception of hydrogen)- to the right of the
zigzag line
Nonmetals are very poor conductors of electricity and heat and may be transparent
Solid nonmetals are not malleable or ductile
They are brittle and shatter when hammered
At 300 C some are solids- carbon (C), other are liquid – bromine (Br) and still others are gases- helium
(He)
Metalloids
Six elements are classified as metalloids – these are situated between the metals and nonmetals and
have both metallic and nonmetallic properties
Boron (B)
Germanium (Ge)
Silicon (Si) Arsenic (As)
Antimony (Sb)
Tellurium (Te)
Mrs.Semmler’s note: aluminum (Al) is also considered a metalloid by some, as are Polonium (Po) and
Astatine (At)- you are safe if you identify metalloids as bridging the zigzag line.
More on metalloids
Example of both characteristics: silicon is used in computer circuits and power strips as it will only
conduct electricity at certain temperatures. If the temperature of the circuit gets too high, the silicon
chips in the circuit will shut down until the temperature lowers.
This semi-conductor property keeps appliances and computers from becoming damaged during power
surges.
** note: Germanium would make a better semi-conductor than silicon (it is located closer to the metals)
but silicon is much more abundant (hence cheaper)
Periods and Groups
Horizontal rows – Periods
The properties of elements gradually change as you move across a period
This is called a periodic trend
One example of a periodic trend is that the size of atoms increases as you move from the lower
left to the upper right corners of the table
Another important periodic trend is how easily atoms lose electrons- some atoms hold on to
their electrons tightly- others give them away readily.
Atoms on the lower left side of the table lose electrons easily. For atoms to the upper right,
however, losing electrons is difficult.
Vertical Columns- Groups (sometimes also called Families)
Down any group, the properties of elements tend to be similar (so they are said to be ‘grouped’ or ‘in
the same family’)
Group names
Some of these groups have special names- read pgs 318 and 319 to find out more
Group 1 – alkali metals
Group 2 – alkaline earth metals
Group 16 – chalcogens
Group 17- halogens
Group 18- noble gases- unreactive gases
Transition metals
Elements of groups 3 through 12 are called transition metals because of their central location
Tend to be harder than the alkali metals and less reactive with water so they are used for structural
purposes
Most notable transition metals- iron (Fe), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag) and gold
(Au)
Lesser known but important for their non-corrosive properties are titanium (Ti), molybdenum (Mo)
and manganese (Mn) – used in implant devices for things like hip replacements.
Inner Transition Metals
Lanthanide series – atomic numbers 58 to 71
Similar physical and chemical properties
Tend to be found in the same locations on earth
Difficult to purify
Some lanthanide elements are used in the fabrication of light-emitting diodes (LEDs) of
computer monitors and flat-screen TVs.
Actinide series – atomic numbers 90 to 103- although elements heavier than uranium are not found
naturally on the planet but are synthesized in laboratories (man-made)
Likewise have similar properties and are difficult to purify
Causes a problem for the nuclear power industry that requires purified samples of uranium
(U) and plutonium (Pu)
16.7 Elements to Compounds
Element is generally used an entire macroscopic or microscopic sample.
Atom is used when talking about the submicroscopic particles in a sample.
Example- gold is an element that is made up of gold atoms
The fundamental unit of an element is indicated by its elemental formula.
For most elements the fundamental unit is made up of one atom; others can form molecules
Gold exists in single atom units for the fundamental unit is Au.
Seven elements (diatomic elements) can only be found in pairs: N2, O2, H2, F2, Cl2, Br2, I2
Compounds
When atoms of different elements bond to one another, they form compounds.
A compound is represented by a chemical formula
Example: sodium atoms and chlorine atoms bond to form the compound sodium chloride, NaCl
Nitrogen atoms and hydrogen atoms bond to form the compound ammonia, NH3
Subscripts (the small lowered numbers) indicate the ratio in which the atoms combine (there is one
nitrogen atom for every three hydrogen atoms)
Note: if there is only one atom, we don’t use the number ‘1’.
Other examples
Naming Compounds
To name compounds, there are some questions you must answer about the compound. Your answer
will determine how the compound is named.
Is the compound only two elements – a metal and a non-metal? Use guideline 1
Or is the compound only two elements – two non-metals? Use guideline 2
Or, is the compound made up of more than two elements? Use guideline 3
Guideline 1 – metal/non-metal binary(two element) compounds
The first element retains its elemental name
The second element adds an –ide ending to its root name
NaCl – sodium chloride (was chlorine)
CaF2 – calcium fluoride (was fluorine)
Li2O – lithium oxide (was oxygen)
Sr3P2 – strontium phosphide (was phosphorus)
Metal/nonmetal compounds using metals that can form more than one charge
Some atoms can form ions that can have more than one charge
Ex- Fe (iron) can form two types of ions
Fe +2 or Fe+3
Cu (copper) can form two types of ions
Cu+2 or Cu+1
These metals require a roman numeral denoting the charge of the ion used
FeS – iron (II) sulfide
Fe2S3 – iron (III) sulfide
CuO – copper (II) oxide Cu2O – copper (I) oxide
Guideline 2 – 2 non-metal compounds
The first element retains its elemental name
The second element adds an –ide ending to its root name
Both elements get prefixes indicating how many of each are in the compound
Commonly used prefixes
1 – mono
2 – di
3- tri
4- tetra
5- penta
6- hexa
7- hepta
8- octa
9 – nona
10- deca
Examples
Note: don’t use mono for the first element
Also- O-O combination drop one of the O’s
A-O combination drop the O
CO – carbon monoxide (not monocarbon monooxide)
N2O4 – dinitrogen tetroxide (not dinitrogen tetraoxide)
N2P4 – dinitrogen tetraphosphide
Guideline 3- compounds made up of more than two elements
The compound will contain a polyatomic ion
Polyatomic ions are groups of elements that have a charge and special names that are used.
Follow the general rules for naming (either using the elemental name for the first element or
changing second element name to an –ide ending for the second element) and use the polyatomic ion
name
Polyatomic ions
Examples
SO4+2 – sulfate
NH4+1 – ammonium
NO3-1 – nitrate
NO2-1 - nitrite
CO3-2 - carbonate
Compounds that contain polyatomic ions
NaSO4 – sodium sulfate
FeSO4 – iron (II) sulfate
NH4O – ammonium oxide
NH4OH – ammonium hydroxide
Cu2CO3 - copper (I) carbonate