CATIONS

 

Easy:  These cations have only one oxidation state.  The name of the ion is the same as the name of the element in both the IUPAC (Stock) and classical systems.

 

1+ :      Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , Ag ⁺ , NH₄⁺ , (ammonium)

2+ :      Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ , Cd ²⁺

3+ :      Al ³⁺

 

Difficult:  These ions have two (or more) oxidation states.

            IUPAC uses Roman numerals ( I, II, III, IV, V, VI ) to indicate oxidation state

            Classical uses word endings to indicate to indicate oxidation states.  Some of these stems are derived from the             Latin name for the element.            stemous indicates the lower oxidation state

                                                            stemic indicates the higher oxidation state

 

1+, 2+
	Cu +	copper(I)	cuprous	Hg 2 2+	mercury(I)	mercurous
	Cu 2+	copper(II)	cupric	Hg 2+	mercury(II)	mercuric
2+, 3+
	Co 2+	cobalt(II)	cobaltous	Cr 2+	chromium(II)	chromous
	Co 3+	cobalt(III)	cobaltic	Cr 3+	chromium(III)	chromic
	Fe 2+	iron(II)	ferrous	Mn 2+	manganese(II)	manganous
	Fe 3+	iron(III)	ferric	Mn 3+	manganese(III)	manganic
	Ni 2+	nickel(II)	nickelous	Mn 4+	manganese(IV	?
	Ni 3+	nickel(III)	nickelic
2+, 4+
	Pb 2+	lead(II)	plumbous	Sn 2+	tin(II)	stannous
	Pb 4+	lead(IV)	plumbic	Sn 4+	tin(IV)	stannic
3+, 5+
	As 3+	arsenic(III)	arsenous	Sb 3+	antimony(III)	antimonous
	As 5+	arsenic(v)	arsenic	Sb 5+	antimony(V)	antimonic

 

ANIONS

 

Monatomic:  binary compounds ( the ion may be used more than once in the formula, i.e.  Al₂S₃ )

                        anion name = (stem)ide,  i.e.  H ^– is hydride.

1– :       H ^– (hydr),  F ^– (fluor),  Cl ^– (chlor),  Br ^– (brom),  I ^– (iod) 

2– :       O ^2– (ox),  S ^2– (sulf, in acids = sulfur)

3– :       N ^3– (nitr),  P ^3– (phosph,  in acids = phosphor),  As ^3– (arsen),  Sb ^3– (antimon)

 

Polyatomic:  (named as though binary)

 

1–:        OH ^– (hydroxide),  CN ^– (cyanide)

2–:        O ₂^2– (peroxide)

 

Polyatomic:  ( oxoanions — ternary or higher)

 

1–
	C2H3O2 –	acetate	NO3 –	nitrate	ClO –	hypochlorite
	HCO3–	hydrogencarbonate bicarbonate	NO2–	nitrite	ClO2–	chlorite
	SCN–	thiocyanate	BrO3 –	bromate	ClO3 –	chlorate
	MnO4–	permanganate	IO4 –	periodate	ClO4 –	perchlorate
2–
	CO3 2–	carbonate	CrO4 2–	chromate	SO4 2–	sulfate
	C2O4 2–	oxalate	Cr2O7 2–	dichromate	SO3 2–	sulfite
3–
	AsO4 3–	arsenate	PO4 3–	phosphate
	AsO3 3–	arsenite	PO3 3–	phosphite

 

Numerical prefixes:

             1 - mono    2 - di                 3 - tri                 4 - tetra             5 - penta    6 - hexa                      

            7 - hepta    8 - octa             9 - nona            10 - deca

 

Binary acids:              hydrostemic acid    (stem is stem of the anion name)

 

oxoacids:

            oxoanion ending in stemate becomes stemic acid

            oxoanion ending in stemite becomes stemous acid

 

Equivalents, Equivalent Weight, and Normality

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Stoichiometric calculations are performed using moles and mole ratios (obtained from a chemical formula or balanced equation).  However in the laboratory, when working with unknowns, it is necessary to work with equivalencies.  Then x equivalents of reagent A will completely react with the same number of equivalents of reagent B (i.e. x equivalents of B).  One equivalent of a reagent is that amount of reagent that will produce (or use) one mole of electrons.  In acid base reactions, where there is no electron change, we can consider the potential number of electrons.  One mole of H⁺ ions could gain one mole of electrons to form one half mole of H₂ (g).   1 H⁺   +   1 e^–  =   ½  H₂ (g)  .  Using a to represent the number of equivalents (eq) per mole, we can relate the equivalent weight (or equivalent mass) to the formula weight (or formula mass) by

 

equivalent weight   =   formula weight / a

 

or for short

 

eq wt  =  f wt / a

 

Where a can represent 

 

Just as we defined

 

molarity (M)  =  (moles of solute) / (liters of solution)  or  M  = moles/L ;

 

 

normality (N)  =  (equivalents of solute) / (liters of solution)  or  N  =  eq/L.

 

 

equivalents of solute (eq)   =  mass / equivalent weight  or  eq  =  m / eq wt

 

 

N  =  a M .

 

            The reason for introducing equivalents is so we can write

 

eq_A  =  eq_B

 

 

L_AN_A  =  L_BN_B