The Composition of Chemical Compounds
Dr. Jared Heidinger M.D. Ph.D
• When neutral atoms collide,
an electron is transferred
from one atom to the other
• Ions – particles that have an
electrical charge due to a
transfer of electrons
• Monoatomic ions – single
atoms that have lost or
gained electrons
• high reactivity due to unfilled
or overfilled electron levels
• Cations - + charged ions
(metals, formed when they
lose an electron)
• Anions – neg. charged ions
(non-metals, formed when
they gain an electron have ide ending)
• When an atom loses an
electron its charge changes
from neutral to positive
• eg. Na - 1 electron = Na+
• The Na atom now has 11
protons and 10 electrons.
• The sodium atom now has a
net positive charge.
• When an atom gains an
electron its charge changes
from neutral to negative
• eg. Cl + 1 electron = Cl
• The Chlorine atom now has
17 protons and 18 electrons.
It has a net neg. charge
• Atoms or groups of atoms
with a net(overall) negative
or positive charge are called
ions.
• ASSIGN – pg. 68 - #’s 14,
17, 18
• “10-2” Worksheet and
“Atomic Structure” side two Ions
• Compounds contain two or
more elements
• Evidence - electrolysis
(electro = electrical; lysis =
loosen)
• Large scale electrolytic cells
are used to produce
separate water into oxygen
and hydrogen gas which can
then be used in industry
• Industries use this quality for
electroplating cars(chrome)
• Remember: phys. And chem.
charac. Of elements relate
directly to the number of
protons and electrons its
atom contains.
Two types of ions:
• Monoatomic ions(simple
ions) - form from the atoms
of an element
• eg. Cl forms Cl
• Polyatomic ions(complex
3ions) - PO4
ionic compounds
• In a chem. Rxn. The #’s of
protons and neutrons do not
change.
• Valence electrons are
involved in chemical
reactions
• for elements to join and
become compounds, they
must form chemical bonds
• chemical bonds: bonds
resulting from the forces of
attraction between atoms
• Ions are attracted to nearby
ions of opposite charge.
• The force that holds any two
oppositely charge ions
together is an ionic bond.
• In a substance many of
these attractions make it
possible for the compound to
stay together.
• This interaction between and + charges gives stability
to the substance
• This explains why ionic
compounds are solids at
room temperature
Formation of a
Compound
• When a compound is
formed, the sum of the
charges must be zero
• eg) 1 negative charge + 1
positive charge = zero
• so...
• eg) When aluminium is in its
ionic form it has a charge of
(3+)
• When chlorine is in its ionic
form it has a charge of (1-)
• When aluminum and chlorine
form an ionic compound the
formula is AlCl3
• It is like this because you
need 3 chlorine molecules
with a (1-) charge to even
out the 3+ charge aluminum
has.
Another example...
• Na+ + Cl- ---> NaCl
• The ion number tells us how
many electrons will be lost or
gained by the element.(ion
number found on periodic
table)
• the overall charge of the
product must be zero
• so if one Na ion has a
charge of 1+ in order for it to
join the chlorine ion it needs
to be balanced by a charge
of negative one.
• Since one chlorine ion has a
charge of negative one only
one is needed. Unlike the
previous example where 3
chlorine atoms were needed.
• The strength of an ionic
bond varies, depending upon
the kinds of atoms involved.
• All ionic compounds share
these similar
characteristics...
ionic compounds:
Characteristics
• metallic and non-metallic
elements
• ionic bonding(transfer of
electrons)
• solutions conduct electricity
• solid at room temperature
Solubility
• If a compound has high
solubility it will dissolve in
water.
• If it is insoluble the
compound will form a
precipitate(visible pieces of
matter, cloudiness in the
solution)
• Highly soluble ionic
compounds can be separated
by using a precipitating
agent such as alum, to make
the soluble compounds
removable.
Assignment
• “Chemistry: Practice Writing formulas”
worksheet
• “Review of Chapter 2: periodicity, atoms,
Ions” Worksheet
• “Ions” workSheet (teach how to use key)
Covalent Compounds
• Non-metal to non-metal
• electrons not transferred,
they are shared
• both atoms attract the
electrons, the electrons can’t
move to either atom, they
find a position in the middle
• The bond that forms when
electrons are shared is called
a covalent bond.
• Substances that are formed
in this way are called
covalent compounds.
• Attraction not as strong as
an ionic bond.
• For this reason, compounds
that are made by covalent
bonding, are also called
molecular compounds
• Molecular compounds are
generally softer than ionic
compounds and exist as
gases, liquids, or solids at
room temperature.
Molecular compounds:
characteristics
• Usually formed from nonmetallic elements only
• covalent bonding (shared
electrons, tug-of-war)
• solutions will not usually
conduct electricity
• solid, liquid, gas at room
temp.
Diatomic and Polyatomic
elements
• some molecular elements are
diatomic and some are
polyatomic in their natural
form
• H2, N2, O2, F2, Cl2, Br2, I2,P4,
S8 (Highlight and
memorize!!!)
Naming Compounds
• IUPAC (International Union
of Pure and Applied
Chemistry)
• makes rules and guidelines
for all aspects of the study of
chemistry
• Handout - Chemical
Nomenclature
Rules for Naming Binary Ionic
Compounds(two elements)
• includes both elements in
the compound
• metallic element name
appears first.
• non-metallic element
appears last, and its ending
is changed to -ide.
Rules continued...
• name does not show the
charge of the elements in
the compound
• name is not capitalized,
lower case letters are used.
• Some compounds have common names
(eg. - water) Become familiar with the
systematic and common name.
Multi-valent ions
• some transition metals have
two possible charges
• eg. Cu has two different ion
forms, Cu+ and Cu2+
• this is a multi-valent ion
• you must know what charge
is being used
• The formation of
copper(I)chloride looks like
this:
+
• Cu +Cl ---> CuCl
• one positive charge is
neutralized by one negative
charge
• The formation of
copper(II)chloride looks like
this:
2+
• Cu +Cl ---> CuCl2
• The copper ion has two positive
charges.
• This indicates that there need
to be two negative charges
added to neutralize it.
How do you write the word formula with
multivalent compounds?
• You must indicate the charge
that is being used with
roman numerals
• CuCl2 - copper(II)chloride
• Fe2O3 - iron(III)oxide
• “Ionic Naming Practice”
• Ionic and Molecular Naming
Worksheet
Acids
• Acid - aqueous hydrogen
compound that makes blue
litmus paper turn red
• ph of less than 7
• hydrogen written first most
of the time, unless it comes
at the end of a COO- group,
like CH3COOH(aq)
Naming Acids
• refer to chart on the periodic
table you received
• start by naming the
compound as an ionic
compound, then check to
see if there is an (aq), if
there is it is an acid
• H2SO4(aq) - hydrogen
sulphate --> sulphuric acid
• CH3COOH(aq) - hydrogen
acetate --> acetic acid
Bases
• all aqueous solutions of ionic
hydroxides (anything
dissolved in water that has a
hydroxide ion attached)
make red litmus turn blue
• ph more than 7
Naming Bases
• the name of the base is the
same as the name of the
ionic name
• NaOH(aq) - aqueous sodium
hydroxide
• Ba(OH)2(aq) - aqueous barium
hydroxide