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Nomenclature - The Science of Naming

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rob snodgrass

on 25 September 2018

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Transcript of Nomenclature - The Science of Naming

Nomenclature -
The Science of Naming

CATIONS WITH MORE THAN 1 POSITIVE CHARGE.
Certain metals can form more than 1 cation. These are usually the transition metals. (REMEMBER: GRP. 1A AND GRP. 2A FORM ONLY 1 CATION: GRP. 1A +1, GRP. 2A +2.)
Iron forms 2 cations: Fe3+ and Fe2+. You must distinguish between them because they are both iron ions.
These ions are named 2 ways:
1. OLD WAY (using Latin roots)
TO NAME: Use the Latin root of the element. Use the ending “ic” for the most positive cation and “ous” for fewest positives. Add the word “ION”.
Fe3+ ferric ion Pb4+ plumbic ion
Fe2+ ferrous ion Pb2+ plumbous ion
2. NEW WAY – Called the STOCK SYSTEM.
A Roman Numeral in brackets is used to designate the number of + charges. (I = 1, II = 2, III = 3, IV = 4, V = 5, VI = 6, VII = 7)
TO NAME: Write the element name, the Roman numeral in brackets, and the word “ION”.
Fe3+ iron (III) ion Pb4+ lead (IV) ion
Fe2+ iron (II) ion Pb2+ lead (II) ion
Remember, the lower charge gets ~ous and the greater charge gets ~ic
Remember, the Roman numeral is the charge!
OR
Ionic compounds
- This means that you need to know how to identify, name, & write the formulas for cations and anions!
In chemistry, you need to learn the rules for naming:
Binary molecular compounds
- These are composed of nonmetal atoms covalently bonded together. Therefore, you need to remember prefixes and the rules for naming the first and second nonmetal.
Ex. CO is
carbon

di
ox
ide
Acids
- There are binary acids (HBr) and ternary acids HNO .
3
2
Phosphate PO
3-
4
Hydrogen phosphate
HPO
4
2-
Dihydrogen phosphate
H
2
PO
4
-
Phosphoric acid
H
3
PO
4
Things are not always what they seem!
Go with what you know!
Group 1 metals are always +1 and group 2 metals are always +2.
Metal hydrides - These are ionic hydrides, in which a metal cation is attracted to an anion of hydrogen.
The metal will have a positive oxidation value and the hydrogen anion will have a oxidation # of -1.
Li
+
H
-
H
-
Li
+
EXCEPTION FOR HYDROGEN WHICH IS USUALLY +1
Peroxides
O
2
2-
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion,
O
.
2
2-
Hydrogen peroxides
Peroxides of alkali & alkaline earth metals
H O
2
2
2(+1) = +2
2(-1) = -2
Go with what you know. This is not a metal hydride, so H must have an oxidation value of +1. There are 2 H atoms, so OVERALL it is +2!
Therefore, oxygen must have an OVERALL value of +2 but there are TWO oxygen atoms, so the oxidation value of
each
oxygen is
-1
, resulting in a
peroxide
!
Na
O
2
2
2(+1) = +2
2(-1) = -2
Mg
O
2
Mg = +2
So oxygen must
be -2 but there are
two of them so oxygen is -1
, resulting in a peroxide!
2(-1) = -2
Nitrogen monoxide
NO
Nitrogen dioxide
NO
2
Dinitrogen tetroxide
N O
2
4
Monatomic Cation Names
The names of monatomic cations always start with the name of the metal, sometimes followed by a Roman numeral to indicate the charge of the ion.
For example, Cu+ is copper(I) ion, and Cu is copper(II) ion.
The Roman numeral in each name represents the charge on the ion and allows us to distinguish between more than one possible charge.

2+
If the atoms of an element always have the same charge, the Roman numeral is unnecessary (and considered to be incorrect).
For example, all cations formed from sodium atoms have a +1 charge, so Na+ is named sodium ion, without the Roman numeral for the charge.
The following elements have only one possible charge, so it would be incorrect to put a Roman numeral after their name.

The alkali metals in group 1 are always +1 when they form cations.

The alkaline earth metals in group 2 are always +2 when they form cations.

Aluminum and the elements in group 3 are always +3 when they form cations.

Zinc and cadmium always form +2 cations.

Although silver can form both +1 and +2 cations, the +2 is so rare that we usually name Ag+ as silver ion, not silver(I) ion. Ag2+ is named silver(II) ion.
More on cations with more than one charge.
Cation ion rules
Carbon tetrahydride
C
H
H
H
H
CH
4
Main Group - Includes all elements of the periodic table except for the transitions.
Silicon tetrachloride
Tetraphosphorus decoxide
Nitrogen trifluoride
Dichloride heptoxide
Carbon disulfide
Disilicon hexabromide
Cl Br
3
3
P O
2
5
NH
3
SO
2
NO
2
N O
2
4
Ammonia is NH
Ammonium is NH
3
but if you
add a H+
then you get...
This is a common
covalent compound
This is a
common
polyatomic
cation.
4
+
Carbon is sharing its valence electrons with hydrogen's valence electrons!
Organic
Molecule

Substances in their ELEMENTAL or FREE STATE have an oxidation value of zero.
Any metal in its elemental or free state has a value of 0.
Ex. Fe is the symbol of iron as a normal element, so Fe = 0
The thing to remember is that there are nonmetals that exist as DIATOMIC MOLECULES in their ELEMENTAL STATE.
Ex: H O N F Cl Br I
2
2
2
2
2
2
2
Cu
Fe
Oxygen gas
LEARNING THE RULES TO NAMING AND WRITING THE FORMULAS FOR IONIC COMPOUNDS, COVALENT COMPOUNDS, AND ACIDS.
+1
+2
+3
+/-4
-3
-2
-1
0
Monatomic cations
keep the name of the metal atom. Ex. Na is a sodium ion
+
Monatomic anions
change their suffix to "ide".
Ex. N is a nitride ion.
-3
Transition metal cations with more that one charge
have different properties; therefore, their stock names and Latin names are different.
Ex. Cu is called copper (I) ion (stock name) and cuprous ion (Latin name)

BUT

Cu is called copper (II) ion (stock name) and cupric ion (Latin name).
+
+2
Basic Rules to Know for Naming:
Cations
are positively charged ions and
anions
are negatively charged.
Polyatomic anions
can end in either "ate" or "ite" depending on the amount of oxygen atoms it possesses. Therefore, some of these are referred to as oxyanions.
Ex. PO is called phosph
ate
but if it has one less oxygen atoms, then it is has the formula. PO and is called phosph
ite
.
The oxyanions that end in "ate" are said to be the most common forms.
4
-3
3
-3
I
strongly suggest making flashcards
to
memorize the names
of ions, ionic compounds, binary molecular compounds and acids!

NAMING ACIDS
Acids are substances that have a high concentration of hydrogen ions, H+.
Acids have a pH below 7 and are often corrosive to metals.
My suggestion in naming acids is to break it up into hydrogen ion and the ion that it has combined.
HClO
Ex.
H+
ClO
-
this is hypochorous ion
Hypochlorous acid
binary acids
ternary acids
Break It Up and then use the naming rules!
Want to determine the FORMULA from the acid NAME?
Ex. #1) Hydrobromic acid: Binary acid use "hydro" and `ic suffix
H+
Br-
Now put it together by balancing out the charges. Notice that this is 1:1 so it is HBr.
Ex. #2) Ternary acids do NOT use "hydro" and you need to understand that polyatomic oxyanions that end in "ate" changes to "ic" AND "ite" changes to "ous".
carbonic acid:
Understand that this is composed of carbonate because it has "ic" ending. Now, remember the formula for carbonate, which is CO and each hydrogen has a +1 charge. Therefore, TWO hydrogens are needed to balance the charge from carbonate ion!
3
2-
H CO
2
3
Try it with phosphoric acid!
3 H+ + PO
4
3-
H PO
3
4
Basically, you need to break it up into the hydrogen ions and the anion. The anion is negatively charged so you will need the appropriate hydrogen ions to balance the charges.
Please remember the three ionic compound NO-NO's
1) Do NOT leave any charges in your ionic formulas!
Ex. of this no-no: MgCl
2-
This actually makes no sense
because each magnesium ion is +2 and each chloride is -1; therefore, you need 2 chloride ions to balance out the +2 charge from magnesium.
Correct example:
Mg + 2Cl MgCl
2
2+
-
2
2) Do NOT include numerical prefixes in the names of ionic compounds! Numerical prefixes are reserved for binary molecular compounds ONLY.
Ex. of this no-no: magnesium dichloride.
It is simply magnesium chloride.
MgCl
2
3)
No NOT name nonmetals before metals. Metals are ALWAYS named before nonmetals in any ionic compound!
Ex. of this no-no: chloride magnesium or Cl Mg
2
It is correctly named magnesium chloride
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