Chem 20 - Naming Compounds



POSITIONING correctly within the formula: On the left is the element with the lower electronegativity. This also means it has the lower group number (column) in the periodic table.					If or is Oxygen and the other is a Halogen, then the position of the Oxygen is on the right side, i/e. .
If and are in the same column in the periodic table, then the element that is lower (larger atomic size) goes first (left) in the formula.

				Continued: Each piece contributes a part of the name.


		handle n		handle k

n = 1 ?					The value of k always gets a Greek Numeral, even if it's 1.

Yes	No
					gets its ionic name, i.e. stem + -ide
Do not prefix with Greek numerals. Do not say mono at the beginning!	is it Hydrogen		?
elemental name (no prefix).	Yes	No		Insert a space between the two components.	Greek Numeral + ionic name as + ide
	n > 1 => Prefix with Greek Numerals.
	Greek Numerals + elemental name.

Examples:

BrO₂ = bromine dioxide <--- no mono at beginning

SiO₂ = silicon dioxide

H₂O = dihydrogen monoxide (this is the IUPAC name of water)

H₂S = hydrogen monosulfide (IUPAC)^§	<-- mono in the middle is ok ^§Additional names are available because H₂S is also a binary acid. H₂S= dihydrogen sulfide, dihydrogen monosulfide, hydrogen sulfide,and hydrosulfuric acid^§ are used as well.
N₂O₄ = dinitrogen tetroxide
N₂O₃ = dinitrogen trioxide
N₂O = dinitrogen monoxide	Commonly known as Nitrous Oxide. dinitrogen oxide is also an accepted name.
B₂Br₄ = diboron tetrabromide
BrF₅ = bromine pentafluoride
AsH₃ = arsenic trihydride	Metaloid (As) Example Notice compounds with Hydrogen as the second use the name of the hydrogen ion: hydride.

Compounds for which Common Names are prefered:

H₂O₂ = dihydrogen monosulfide,but hydrogen peroxide is often used instead.

O₃ = ozone is used instead of the IUPAC name.

P₄ = red phosphorous is used instead of the IUPAC name.

Caveat:

Paying attention to the charge...

SPECIAL CASES:

SO₃ = is a neutral, covalent gas (at room temperature).


is SO₃ an ?		SO₃ = sulfur trioxide, is based on the current naming scheme.This is so because SO₃ is not charged.

How about SO₃^2- ?		SO₃^2- = is a solid crystal lattice ion in aqueous solution. It is negative and pairs up with cations in ionic compounds. SO₃^2- is a , namely an oxyanion. You must notice the charge. This is acombination, not a . The naming scheme is different than the current one. It is based on oxyanion naming with a baseline of n= 4. SO₃^2- = sulfite.

Covalent Bonding

All compounds involving non-metals are essentially covalent with the exception of NH₄⁺, in which case the bond is ionic.

Covalent compounds have no net charges, and can have no ions in them. See caveat.

The

position on the left side is chosen for the element that has the lower electronegativity.

Identical atoms bond to each other (diatomics)

is acceptable, O₂ and H₂ are valid formulas and follow the naming scheme.

Notice that the

combinations always require Greek numerals for the second position on the right.

Greek Numerals

Greek Numerals Use
Never duplicate your "o"-s when naming:
for ex.
mono + oxide is not monooxide, but rather monoxide.

When a name forms "a" + "o", the "a" can be dropped but it's not mandatory. For example:
tetra + oxide

tetra + oxide

tetroxide
penta + oxide

penta + oxide

pentoxide

For ex., pentaoxide and pentoxide are both correct. The dropping of the "a" is the more common form.

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