Download Chemistry Review - Grade 11 & 12 Notes

Chemistry Review
Chapter Outline
• What are atoms?
• How do atoms interact to form molecules?
• Why is water so important to life?
What are Atoms?
• All matter is composed of very small
particles called atoms
• Atoms themselves are composed of
smaller, subatomic particles called
protons, neutrons and electrons
What are Atoms?
Name of
Particle
Location of Charge of
Particles
Particle
Mass of
Particle
Proton
Nucleus
Positive
1 amu
Neutron
Nucleus
Neutral
1 amu
Electron
Orbits
around
nucleus
Negative
1/2000
amu
What are Atoms?
• Bohr Model of the Sodium Atom
What are Atoms?
• There are approximately 100 different
types of atoms
• These correspond to the 100 elements
present on the Periodic Table of the
Elements
• Elements on the Periodic Table are
organized by atomic number, atomic
mass, and similar properties
What are Atoms?
• Atomic Number =
# of protons =
# of electrons
Atomic Mass =
# of protons +
# of neutrons
What are Atoms?
•
•
•
•
Using the Periodic Table
# protons= atomic number
# electrons= atomic number
# neutrons= atomic mass – atomic number
What are Atoms?
• The protons and neutrons are in the
central nucleus
• Electrons arrange themselves into distinct
orbitals around the nucleus
• The first orbital nearest the nucleus holds
a maximum of 2 electrons
• The remaining outer orbitals hold a
maximum of 8 electrons each
• For example, sodium is atomic number 11
and atomic mass 23
• #protons= 11
• #electrons= 11
• #neutrons= 23-11 = 12
• The sodium atom has 11 electrons: 2, 8
and 1 electron in the outer orbital
What are Atoms?
• For example, chlorine is atomic number 17
and atomic mass 35
• #protons= 17
• #electrons= 17
• #neutrons= 35 – 17 = 18
• The chlorine atom has 17 electrons: 2, 8,
and 7 electrons in the outer orbital
How do atoms interact to form
molecules?
• The Octet Rule states that atoms are most
stable if the outer orbital is either full (8
electrons) or empty (0 electrons)
• Atoms will lose or gain electrons in order
to fill the orbital and achieve stability
• When atoms lose or gain electrons, they
become charged atoms called ions
How do atoms interact to form
molecules?
• For example, sodium has one outer
electron and will lose the one electron in
order to become stable → +1 sodium ion
• For example, chlorine has seven outer
electrons and will gain one electron in
order to become stable → -1 chlorine ion
How do atoms interact to form
molecules?
• Ions of opposite charge attract to form
ionic compounds
• +1 Na ion + -1 Cl ion → NaCl compound
• The bond that keeps the ions together is
called an ionic bond
What are Atoms?
• Outer orbitals of Na and Cl ions
How do atoms interact to form
molecules?
• Metallic and non-metallic elements on the
periodic table form ionic compounds by
losing/gaining electrons
• Non-metallic and non-metallic elements
form covalent compounds by sharing
electrons
How do atoms interact to form
molecules?
• For example, H atom has one outer
electron: it needs one more electron to
become stable
• C atom has four outer electrons: it needs
four more electrons to become stable
• Four H atoms will share their electrons
with one C atom so the C atom will be
stable
How do atoms interact to form
molecules?
• One C atom will share its four electrons
with four H atoms in order for the H atoms
to become stable
• The bond that forms between the atoms is
called a covalent bond: the equal sharing
of electrons between atoms
How do atoms interact to form
molecules?
• Outer orbitals of H and C atoms
How do atoms interact to form
molecules?
• Non-metallic and non-metallic atoms do
not always share their electrons equally
• For example, H and O are non-metallic
elements
• When H and O atoms share electrons, the
O atom has a stronger pull on the H
atom’s electrons → the O atom becomes
slightly negative, the H atom slightly
positive
How do atoms interact to form
molecules?
• This unequal sharing of electrons creates
a polar covalent bond between H and O
atoms
• The molecule as a whole has no net
charge, but there are distinct poles of
charge
• The molecule is a polar covalent
compound
Why is water so important to life?
• Water is a polar covalent molecule held
together by polar covalent bonds between
H and O atoms
Why is water so important to life?
• Because water is a polar covalent
molecule, the slightly positive H regions of
one water molecule will attract the slightly
negative O regions of another water
molecule
• This electrical attraction between the water
molecules is called hydrogen bonding
Why is water so important to life?
Why is water so important to life?
• The extraordinary properties of water are
due to water’s intramolecular polar
covalent bonds and intermolecular
hydrogen bonds
Why is water so important to life?
• Water is a good solvent: it interacts with
many other molecules that are ionic or
polar covalent
• Water molecules are cohesive (stick
together) due to hydrogen bonding
between water molecules
Why is water so important to life?
• Because of hydrogen bonding between
water molecules, it takes a large amount
of added energy to change water from
solid→liquid→gas (energy of vaporization)
• Because of hydrogen bonding between
water molecules, one must remove a large
amount of energy in order to change water
from gas→liquid→solid (energy of fusion)
Why is water so important to life?
• Water can dissociate (separate) into +1 H atoms
and -1 OH ions in a solution
• The amount of +1 H ions vary within and
between biological and chemical systems
• Systems that have an excess of +1 H ions are
described as acidic
• Systems that have an excess of -1 OH ions are
described as basic
• Systems that have equal amounts of +1 H ions
and -1 OH ions are described as neutral
Why is water so important to life?
• The pH scale measures the degree of
acidity/ alkalinity in a system
• Acidic < pH 7
• Neutral = pH 7
• Basic > pH 7
• A chemical that ends to maintain a
solution at a constant pH is called a buffer
• When the solution becomes too basic,
buffers release +1 H ions into the solution
to decrease pH
• When the solution becomes too acidic,
buffers collect and remove +1 H ions from
the solution in order to increase pH