Download Chemistry Unit Notes Organizing the Periodic Table All the elements

Chemistry Unit Notes
Properties of Matter
Organizing the Periodic Table
Matter is anything that takes up space and has mass.
All the elements in a column on the table are called a chemical group. These
elements have similar physical and chemical properties. These elements also form
similar kinds of compounds when they combine with other elements.
The Noble Gases
The last column of elements on the periodic table is referred to as the noble gases.
These gases are unreactive and almost never form compounds with other elements.
Physical Properties
A physical property is a characteristic or description of a substance that may help to
identify it. A physical property does not involve a substance becoming a new
substance.
Example: colour, texture, odour, lustre, clarity, or taste.
1.
Alkali Metals
The first column of elements on the periodic table is referred to as the alkali metals.
These elements are all shiny, silvery metals that are extremely reactive. Because they
combine so easily with other elements they are only found in nature in the form of a
compound.
The States of Matter – whether matter is a solid, liquid or gas at room
temperature.
State
Solid
Liquid
Halogens
Gas
th
Fluorine, chlorine, bromine and the other halogens occupy the 17 column on the
periodic table. The halogens are the most reactive non-metals and they almost always
appear in nature in the form of a compound.
Rows on the Periodic Table
The elements that are found side-by-side show similar properties and gradual changes
in these properties. These horizontal rows are called periods. As you move from left
to right in a row the atomic number increases and the elements change from metals to
nonmetals to the noble gases.
Has a fixed volume
Has a fixed volume
Always fills the entire
container
Hardness – is a measure of the resistance of a solid to being scratched or dented.
A harder material will scratch or dent a softer one.
Example: diamonds are harder than glass.
3.
Malleability – if a solid is malleable it can be hammered or bent into different
shapes.
Example: Aluminum foil
Ductility – is when a solid can be pulled into long, thin wires.
Example: Copper is used for electrical wiring
4.
Metalloids
Elements that have both metallic and nonmetallic properties are called metalloids.
These are the elements that make up the staircase on the periodic table.
Has a fixed shape
Always takes the shape
of its container
Always takes the shape
of its container
Volume
2.
Hydrogen
Hydrogen is in a group of its own because it is unique to all other elements on the
periodic table. Hydrogen has the ability to react like a metal as well as a non-metal.
Hydrogen exists in combinations with other elements.
Shape
5.
Melting and Boiling Points – the temperatures at which substances change
state.
Example: Ice changes to Water at 0°C, this is known as its melting point.
6.
Crystal Form – some solids form into definite structures of cubes or blocks with a
regular pattern.
Example: grains of salt
7.
Solubility – is the ability of a substance to dissolve in a solvent such as water.
Example: Kool-Aid
Chemical Changes:
8.
9.
Viscosity – refers to how easily a liquid flows: the thicker the liquid, the more
viscous it is (slower).
Example: Molasses flows slower than water
Density – is the amount of matter per unit volume of that matter (kg/m3).
Example: Lead is “heavier” than a feather
Chemical change – the original substance is changed into one or more different
substances that have different properties. Most chemical changes are difficult to
reverse.
Examples: Burning, cooking and rusting.
Clues that a Chemical Change has Happened:
Chemical Properties
A chemical property describes the behaviour of a substance, as it becomes a new
substance.
Example: Dynamite explodes when exposed to a flame because the dynamite
combines with oxygen in the air. This reaction produces new substances.
1. Combustibility – is a property that describes the ability of
a substance to react with oxygen to produce carbon dioxide, water and energy.
Example: Gasoline is flammable or combustible
2. Reaction with Acid – the ability of a substance to react
with acid.
Example: when magnesium metal is added to acid, it produces bubbles of gas and
the metal disappears.





A new colour appears
Heat or light is given off
Bubbles of gas are formed
A solid material (or precipitate) forms in a liquid
The change is difficult to reverse
These clues suggest that a chemical change might be happening; don’t jump to
any conclusions!!! You need to consider several clues in order to determine what
type of change has taken place.
The Particle Theory
The theory that has been used by scientists to explain matter is called the particle
theory of matter.
Physical and Chemical Changes
The particle theory of matter consists of 4 principles:
Some of the most useful and powerful properties of matter are those related to how
and why matter changes.
Example: Freezing water, Applying heat to an Egg, etc…
Physical Changes:
Physical change - the substance involved remains the same substance, even though
it may change state form. Most physical changes are easy to reverse.
Examples:
Changes of states – melting, boiling, freezing, condensation and sublimation
Dissolving – process can be reversed by evaporating the liquid.
1. All matter is made up of tiny particles.
2. One substance is made up of all the same particles and different substances are
made of different particles.
b. It is easier to move your hand through air than through
8. Explain in terms of the particle theory, what happens when:
a. A liquid freezes into a solid
b. A vapour condenses into a liquid.
9. In which type of matter: solids, liquids or gases are the particles
water.
further apart?
Classifying Matter
3. Particles are always moving; the more energy the particles have, the faster they
move.
An atom is a particle found in an element.
A molecule is a combination of two or more atoms. Molecules can be made up of the same atoms or
can be made up of different atoms.
4. There are attractive forces between two particles. These forces are stronger when
the particles are closer together.
For example: Oxygen (O2) – in the element oxygen there are two oxygen atoms in each molecule.
For example: Salt (NaCl) – one atom of Sodium and one atom of Chlorine in each molecule of salt.
Types of Substances
Substances can be classified into two categories using the particle theory of matter: pure
substances and mixtures.
Particle Theory Questions
1. State what happens to the distance between particles when a substance changes
a. from a solid to a gas
b. from a liquid to a solid
2. Why is it easier to compress a gas than a liquid?
3. What causes a solid to have a definite shape and volume?
4. Gas particles are considered to have very little attraction for one another. Explain.
5. Why is a solid iron more dense than liquid iron?
6. Explain why solids, liquids and gases expand when heated. Use the particle
theory.
7. Use the particle theory to explain why:
a. Gases have low density.
A pure substance contains only one kind of particle. For example: a bag of sugar contains only
sugar particles.
Types of Pure Substances
Elements are pure substances that cannot be broken down into simpler substances. Elements are
the “building blocks” of every substance.
For example: Hydrogen (H) or Oxygen (O)
Compounds are pure substances that contain two or more different elements in a fixed proportion.
They are formed when elements combine together in chemical reactions.
For example: Water (H2O) – there are always twice as many hydrogen particles as there are of
oxygen particles.
A mixture contains at least two different pure substances or two different types of particles.
For example: a cookie is made up by a combination of pure substances.
Types of Mixtures
A homogenous mixture (solution) is made up of different substances that cannot be easily seen
when mixed together.
For example: when Kool-Aid crystals are added to water, the crystals disappear as they dissolve.
A heterogeneous mixture is a substance made up of different substances that can be easily seen
and can be separated by physical means.
4. Classify each as a pure substance, homogenous mixture or heterogeneous mixture.
a) Sand b) Salt c) Soil d) Pop e) Air f) Gold g) Salad h) Sugar i) Wood j) Sugar and Water -
Chemical Names and Chemical Formulas
A chemical symbol is an abbreviation for the name of an element.
Example: Al – Aluminum
O – Oxygen
**Notice that a single-letter symbol is always capitalized and that the first letter of a
two-letter symbol is always capitalized and the second letter is not.
For example: garbage or pizza
A chemical formula is the combination of symbols that represents a particular
compound. A chemical formula indicates which elements are found in the compound,
as well as the number of atoms of each element that are found in the compound.
Examples:
NaCl – 1 atom of Na – sodium
- 1 atom of Cl – chlorine
H2O – 2 atoms of H – hydrogen
- 1 atom of O - oxygen
Rules For Naming Ionic Compounds
Questions
1. Make a picture to help explain the differences between;
a) an element and a compound
b) a homogeneous mixture and a heterogeneous mixture.
2. Give two example of molecules that are made from the same element (poster in class).
3. Read the following statements and state whether each description is referring to an element or a
compound.
a) a clear, colourless liquid that can be split into two gases with different properties.
b) a yellow solid that always has the same properties and cannot be broken down.
c) a colourless gas that burns to produce carbon dioxide and water.
1. Metals combine with nonmetals in many compounds.
2. Write the name of the metal first and the nonmetal second.
3. Change the ending of the nonmetal to “ide”.
Rules For Writing The Formulas for Ionic Compounds
1. Metals combine with nonmetals in many compounds.
2. Each atom has its own combining capacity (charge/hooks).
3. Atoms combine so that each atoms combining capacity if full. Each atoms needs to
be “balanced”.
4. When writing the formula the metal symbol is first and the nonmetal symbol is
second.
5. The number of each kind of atom needs to be specified. (H2O)
Counting Atoms
Inside the Atom
Rules for Counting Atoms
When taking a closer look at the makeup of an atom, Scientists have discovered
that most of the atom is empty space that is filled with quickly moving electrons.
At the very core of the atom is a positively charge center called the nucleus.
1. The symbol of an element represents one atom of that element.
Example: Na : 1 atom of Sodium
These parts of the atom are known as the subatomic particles. Scientists have
discovered 3 types of subatomic particles.
2. The subscript number indicates the number of atom for that element.
electron
Examples:
H2 : 2 atoms of Hydrogen
H2SO4: 2 atoms of Hydrogen
1 atom of Sulfur
4 atoms of Oxygen
neutron
proton
3. A subscript outside a bracket multiplies to all the element inside the brackets.
Examples:
Mg3(PO4)2 : 3 atoms of Mg
1*2 = 2 atoms of P
4*2 = 8 atoms of O
Ca4(SO4)3: 4 atoms of Ca
1*3 = 3 atoms of S
4*3 = 12 atoms of O
4. A coefficient is a number written in front of a chemical formula. The coefficient
indicates the number of molecules of that compound. A coefficient multiplies the
number of atoms of each element in the formula
Examples: 2H2O = 2*2 =4 atoms of H and 2*1=1 atoms of O
3CuSO4 = 3*1 =3 atoms of Cu
3*1 = 3 atoms of S
3*4 = 12 atoms of O
4Pb(NO3)2 2 = 4 atoms of Pb
1*2*4 = 8 atoms of N
3*2*4 = 24 atoms of O
The Subatomic Particles
Protons – These particles are positively charged particles that are found in the
nucleus. Protons are very important because the number of protons in the atom
determine what the atom is.
Example: an atom with 8 protons will always be an oxygen atom.
Neutrons – These particles are neutrally charged particles that are found in the
nucleus.
Electrons – These particles are negatively charged particles that are found
traveling in the space around the nucleus.
We represent the numbers of the subatomic particles by using standard atomic
notation.
35
Cl
17
mass number
chemical symbol
atomic number
Counting Subatomic Particles
Fill in the following table.
An atom itself has no electric charge because the number of electrons is equal to the
number of protons found in that atom. Therefore, the positive and negative charges
cancel each other out leaving a net charge of zero.
Atomic
Symbol
Atomic
Number
Atomic
Mass
# of
Protons
# of
electrons
# of
neutrons
B
5
11
5
5
11- 5 = 6
The atomic number found on the periodic table tells us how many protons we have in
each type of atom.
Example: Carbon has an atomic number of 6. How many protons does it have?
The atomic number found on the periodic table tells us how many protons we have in
each type of atom.
Example: Carbon has an atomic number of 6. How many protons does it have?
Answer: 6
The number of electrons found in an atom is exactly the same as the number of
protons found in that type of atom.
Example: How many protons does Lithium have? 3
Charged Atoms (aka. Ions)
Therefore, Lithium also has 3 electrons in each of its atoms.
Atoms can gain or lose electrons to form charged atoms called ions.
We can use the mass number to help us find the number of neutrons found in each
type of atom.
These atoms are called ions because the number of electrons in the atom do not equal
the number of protons in that same atom.
Number of Neutrons =
The element is still the same because the number of protons has not changed.
Mass Number
-
Example: Copper (Cu)
# of neutrons = 64 – 29 = 35
Therefore, Copper has 35 neutrons in each atom.
# of protons
Ions are formed when negatively charged electrons move from one atom to another.
If atoms lose electrons, there are more protons in the nucleus than electrons in the
space around it. Therefore, this type of ion would have a positive net charge.
If atoms gain electrons, there are more electrons than protons. Therefore, this type of
ion would have a negative net charge.
Example:
Name
Atomic
Symbol
# of
Protons
Neon atom
Ne
+10
Lithium ion
Li+
# of
# of Electrons
Electrons gained or lost
-10
none
Lost 1
Si
+33
-36
54

Gained 1
Net
Charge
0