Science 10
Chemistry
Mr McDonald
Matter
http://www.meta-synthesis.com/webbook/31_matter/matter2.jpg
Elements
• We have the periodic table of the elements
• There is order to the table based on
characteristics of the elements
– What are some of these characteristics?
Atoms
• Recall
• Mass number – total number of protons and neutrons
in the nucleus
• Atomic Number – number of protons
• Number of protons is constant but neutron and
electron numbers can be different
– Electrons: be in a full outer shell (if so called an ION)
– Neutrons: be the same as protons but if not it’s an isotope
Electron shells
• For the first 20 elements the shells are:
– 2, 8, 8, (2)
• These are the only electrons that you need to know.
• But after the 20th element the shells can contain more
electrons, based on orbitals.
Various models of the atom
•
•
•
•
Dalton’s – “billiard ball” model
Thomson – “raisin bun” model
Rutherford – “Electron Cloud” model
Bohr – best model to date
Bohr
• Makes an
extension of the
Rutherford model
that the electrons
are at certain
energy levels
from the nulceus
Bohr Diagrams
• Shows the total number of electrons
surrounding the atom
Electron Dot Diagrams
• Used to describe the amount of valence (outer
shell) electrons for each atom.
Review of terms
• Nucleus: The central part of an atom; contains
the protons and neutrons.
• Electrons: small, negatively charged particles.
Are found in electron shells OUTSIDE the nucleus.
• Electron Shells (orbital): 3D space where
electrons are likely to be found.
• Valence electrons: Electrons found in outermost
electron shell. It is these electrons that move
from atom to atom.
• Octet Rule: All atoms strive for a FULLY FILLED
outer (valence) electron shell. For most atoms
(1st row excluded—where 2 electrons is a “full”
shell”), this is eight electrons. Atoms can gain or
lose electrons to achieve an octet (8) of electrons.
Ions
• Ion: An atom that has either gained or lost an
electron to achieve a stable octet of electrons.
– Cation: an atom that has LOST electrons to form a
positively charged ion. Example: Na  Na+ + e– Anion: an atom that has GAINED electrons to
form a negatively charged ion. Example: F + e- 
F- . All elements that form negatively charged ions
have their name changed by adding “… ide” to the
end. Thus, fluorine becomes a fluoride ion.
Compounds
• Binary compounds
– Ionic compounds
• Compound between non-metal and metal
• Conducts electricity in aqueous solution
– Molecular compounds
• Between non-metal and non-metal
Determining formula
• Need to determine the stable ion for each
atom, we write the positive ion first and the
negative ion last
• Take the charge of each element and “crossover” to give how the elements combine
• If you have a factor of one another, can
simplify
• Step 1:
Si4+ O2• Step 2:
Si4+ O2- 
Si2O4
• Step 3:
Si2O4
SiO2
Naming compounds
• Naming of compounds are different
depending on the type of compound (ionic
and molecular)
Naming compounds
• When there are more than one element need to describe
this in the naming.
# of atoms
Prefix
# of atoms
Prefix
1
mono
6
hexa
2
di
7
hepta
3
tri
8
octa
4
tetra
9
nona
5
penta
10
deca
Rules for the Prefix System
• ONLY use the Prefix system for non-metal/non-metal compounds—
NEVER for ionic compounds! (Exceptions: Classical (ous/ic) system:
Used for metal ions with more than two possibilities; also used on
occasion for metalloid compounds.
• If the first element named has only one atom, we do NOT use the
Mono prefix—it is assumed the first element has one atom unless
otherwise specified.
• Compounds where the first element named is hydrogen are acids—
they use an entirely different naming system (see later PPT). Note
that acids are always aqueous solutions; if the element is a gas, it is
named using the prefix system. Example: HCl (g) is called hydrogen
chloride; HCl (aq) is called hydrochloric acid.
• In some compounds, the vowel at the end of the prefix is dropped;
this is done to make the name easier to say. Example: N2O
dinitrogen monoxide (not monooxide). This is usually done when
the second named element starts with a vowel (like oxygen).
Homework
• Pg38
• # 9(NOT #b, #c do Cl),
• 13a,d,f, 15b,c,d, 18a,b,d,e,f
• Draw the ionic form of (charge):
–N
F
Al
Be
Ca
B
Some examples
• Name
– SO2 SO3 OF2 O2F2
• Write formula
– Sulfur difluoride sulfur tetrafluoride
– Sulfur hexafluoride disulfur difluoride
Naming for ionic compounds
• There is no use of prefixes.
• The formula is based on the electron transfer
between the two elements
– Which is based on the ions
• Remember that ionic compounds are more of
a crystal lattice so the formula is just a formula
unit
Some examples
• Name
– LiCl KBr CaCl2 MgO
• Write formula
– Sodium fluoride barium bromide
– Magnesium fluoride aluminium chloride
Using the Stock system
• Some elements can have more than one
cation
• This is used to identify which cation to use
• For example copper(II) is Cu2+ and copper(III) is
Cu3+
Polyatomic Ions
• Different atoms bonded by covalent bonds to
give an ion.
• These are unit when placed in a compound
they are treated as one unit
• When naming these compounds you would
follow the same rules as ionic compounds.
Example
•
•
+
Ammonium NH4
2Sulfate SO4
• If these combine, the cross-over method
would be used to give
+
2• NH4 SO4 -> (NH4)2SO4
• Ammonium Sulfate
Hydrogen Compounds
• Compounds with Hydrogen are a little
different
• They can be acids, or compounds with
hydrogen and carbon.
• We will learn about simple acids in section 2.3
and the hydrogen and carbon compounds in
later chemistry courses.
Seatwork/Homework
• Pg 55 all odd numbered letters and 6
• Naming sheets for compounds