Transcript Writing and Naming Compounds

Writing and Naming
Compounds
ALL METALS have several
characteristics:
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have luster (shiny); some have more luster than others, but all metals
have some shine. All metals are silvery or gray colored except gold and
copper.
Will conduct electricity – some conduct better than others but all metals
will conduct electricity to some degree; gold is considered to be the best
electrical conductor, also silver, copper and aluminum
Ductile – can be pulled out into a wire
Malleable - can be hammered into a thin sheet; some are more malleable
than others; gold is probably the most malleable, followed by silver and
copper.
ALWAYS LOSE ELECRONS FROM THEIR OUTER ENERGY LEVEL TO
FORM POSITIVE IONS WHIH ARE CALLED CATIONS. Since the
positively-charged ion will be attracted to the negative electrode
(opposites attract), the ion attracted to the cathode is called the CATION.
The Roman numeral at the top of the column on the Periodic Chart is the
number of electrons in its outermost energy level, and these are the
electrons which the metal will lose (all of them)
ALL NON-METALS have
opposite characteristics
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do not have luster and are frequently powdery, liquid or gaseous;
most are colored
do not conduct electricity (non-conductors) except some of the
metalloids which are used in computer chips
are not ductile
are not malleable
ALWAYS GAIN ELECTRONS INTO THEIR OUTER ENERGY
LEVEL UNTIL THEY HAVE 8 AND FORM NEGATIVE IONS
WHICH ARE CALLED ANIONS. Since a negatively-charged
particle will be attracted to the positive electrode (opposites
attract), the ion which is attracted to the anode is called the
ANION (opposites attract), the ion which is attracted to the
anode is called the ANION.
The Roman numeral at the top of the column on the Periodic
Chart is the number of electrons in that atoms outermost energy
level, and non-metals must gain enough electrons here to make
a total of 8 in the outermost energy level.
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Positive ions (CATIONS) have more
protons than they have electrons since
metals ALWAYS LOSE electrons. This
results in the ion having a positive
charge.
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Negative ions (ANIONS) have gained
electrons in their outermost energy levels
and therefore have more electrons than
protons. This results in the ion having a
negative charge.
OXIDATION NUMBER
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is the overall charge on an ion after it has lost
electrons (metals) or gained electrons (non-metals).
Oxidation numbers can be determined by looking at
the Periodic Chart for the “A” column elements, but
usually it is easier just to memorize the oxidation
number associated with every ion rather than having
to look it up every time.
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When ions are combined together to form
compounds, THE OVERALL CHARGE OF THE
COMPOUND WHICH RESULTS MUST BE “ZERO”
OR NEUTRAL.
For example
if an ion of potassium (whose charge is +1)
combined with an ion of chlorine (whose
charge is -1), the compound that results is
electrically neutral as written in a 1:1 ratio of
ions i.e. 1 potassium ion with a charge of +1
will exactly neutralize 1 chlorine ion with a
charge of -1, so the formula for the
compound is written simply
KCl (1 K to 1 Cl)
However,
if an ion of magnesium (whose charge is +2 combined
wit an ion of chlorine (whose charge is -1), the
compound that forms must be electrically neutral, so
therefore, it takes 2 of the chlorine ions (with a charge
of -1 each) to neutralize 1 of the magnesium ions
whose charge is +2.
When we write the number which shows us that there
must be more than 1 of a particular ion present to
make the compound neutral is always written as a
SUBSCRIPT.
NOTICE THAT IN WRITING
CHEMICAL FORMULAS, THE
METAL ION IS ALWAYS WRITTEN
FIRST AND THE NON-METAL ION
IS WRITTEN LAST.
Write a correct formula for the compound,
which would form between. (Criss – Cross
Method)
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lithium and fluorine
calcium and sulfur
cesium and oxygen
aluminum and oxygen
sodium and sulfur
aluminum and chlorine
potassium an oxygen
We will basically be writing and naming two different
types of compounds—ionic and molecular, ionic
compounds are those compounds which are made
up of
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a metal and a non-metal
a metal and a polyatomic ion
ammonium ion and a non-metal
ammonium ion and a polyatomic ion
When naming BINARY (2 elements only)
ionic compounds (i.e. a metal and a nonmetal)
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Call the entire name of the metal
Shorten the name of the non-metal (usually
at the 2nd vowel from the end of the word)
and
Add the suffix “ide”
Therefore KCl would be called potassium
chloride, NOT potassium chlorine.
Name the following binary
ionic compounds:
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MgBr2
NaF
Al2O3
CdO
ZnS
Na2O
K 3N
Some metals have more than one oxidation number
and when you name them you must indicate which of
the oxidation numbers you are using.
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There are only 5 elements which you need to memorize which
have more than one oxidation number and they are:
Iron (+3 or +2)
Lead (+4 or +2)
Tin (+4 or +2)
Mercury (+2 or +1)
Copper (+2 or +1)
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some metals were found to have more
than 2 oxidation numbers, so we
adopted a new system of naming
called the IUPAC (international union of
Pure and Applied Chemists) which
uses the element name and a Roman
numeral (in parenthesis) written after
the name. So, we can also name the
compounds copper (1) and copper (II),
iron (III) and iron (II), lead (IV) and lead
(II), tin (IV) and tin (II), and mercury (II)
and mercury (I)
Write correct formulas for the
following
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tin (IV) chloride
iron (III) oxide
Covalent Compounds
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Compounds can also be written which consist of
TWO __NON METALS. In this case, one of the
non-metals must assume a positive oxidation
number. You do not need to worry about which of
the non-metals is more likely to assume the positive
oxidation number—you just need to be able to
recognize that they are “special” compounds and
therefore are named in a “special” way.
When two non-metals combine to form a compound,
it is called a _MOLECULAR COMPOUND
(Covalent).
Naming Covalent Compounds
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To name molecular compounds, we use a series of prefixes
to indicate the NUBER OF ATOMS OF EACH ELEMENT WHICH
ARE PRESENT. These prefixed are not used at any other time
in naming. They are:
1 – “mono” - only used in naming the second element
2 – di
3 – tri
4 – tetra
5 – penta
6- hexa
7 – hepta
8- octa
9 – nona
10 – deca
NAMING
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If you wish to name Cl2O7 a molecular
compound since it contains two non-metals,
use the prefix to indicate how many chlorines
are present and use the ENTIRE first
element’s name (not shortened nor modified)
– dichlorine. Then use a prefix to indicate
how many atoms of the second element are
present and shorten its name at the second
vowel from the end of the name and add “ide”
- heptaoxide.
Naming Compounds
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Example: name the following molecular
compounds
CO2
N2O3
Cl2O
SO3
CO