Molecules and Compounds/Chemical Nomenclature, CH5

A classic error here is to name the compound Fe2O3 as iron(II) oxide because the formula of Fe2O3 showed a "2" subscript.

Remember that the Roman Numeral indicates the CHARGE of the Danger Zone cation, not necessarily the subscript value.

When comparing similar polyatomics...

...those that end in "ate" indicate "more oxygen" while "ite" indicates "less oxygen."

How does the octet rule work?

1) Find the elemental symbol on a PT of the ion you hope to determine. 2) Advance box-by-box to the nearest Group VIIIA element. You may have to move forward (hence gaining negative electrons) or retreat backwards (hence losing negative electrons.) 3) For every box you advance, you are adding one negative charge. 4) For every box you retreat, you are adding one positive charge (since you are losing negatively-charged electrons in this path.)

You must not use Roman Numerals in ionic naming UNLESS the cation is in the Danger Zone.

ALWAYS LOOK AT A PT TO DETERMINE IF YOU HAVE A DANGER ZONE CATION

What is the ionic charge of aluminum ion?

Al 3+

When encountering Danger Zone cations, how do you know which cation charge is present?

Anion charges do NOT vary, so use your anion knowledge to "back out" the cation charge.

What is the ionic charge of bromide ion?

Br -1 (not +7)

Why bother with OLD System?

Common names STILL appear in hospital settings, such as the use of ferrous sulfate to treat anemia (iron deficiency.)

sulfate is SO4 2- while sulfite is SO3 2

The sulfate has more oxygen atoms.

IONIC COMPOUNDS MUST BE ELECTRICALLY NEUTRAL

The total of the negative charges must EQUAL the total of the positive charges

WHEN to use Roman Numerals

These "Danger Zone" cations are located as Transition Metals (B Groups on PT) and the cations under the zig-zag line, except for AL +3 Zn +2 Ag +1

We use the STOCK SYSTEM for nomenclature

This system does the same thing that families do when they have two members with same name- they use Roman Numerals to tell the names apart: Just like as if an Albert Einstein III had a son and named him Albert Einstein IV.

Stock System

Use Roman Numeral in ( ) after cation name WHEN cations can have more than one possible charge.

Name Fe2O3

We know oxide has a -2 charge; there are three of these -2 oxides; the negative total is therefore -6 (because THREE times -2 = -6); the "positive" side must sum to +6 to achieve neutrality; however, there are TWO Fe cations (see the subscripts.); therefore, EACH Fe has to only provide a +3 (because TWO times +3 = +6); then we have the presence of +3 cations. The name of Fe2O3 is iron(III) oxide.

NH4NO3

While there are two polyatomic ions here, there is only ONE of each; do NOT use ( )

another mnemonic sentence to memorize the SEVEN diatomic elements

Have No Fear Of Ice Cold Beer

Example #1: H2 + O2 → H2O (not balanced)

Here you see that "H2O" is a compound so it does not necessarily get a "2" subscript after the oxygen symbol.

a mnemonic sentence to memorize the SEVEN diatomic elements

Horses Need Oats For Clear Brown Iyes (Eyes?)

Problems with OLD SYSTEM

You need to know Latin; need to know BOTH possible charges to award winner. Note that a certain charge number value is NOT associated with a certain ending as shown above. What that means is that "ic" is not always associated with a +2 charge.

The Periodic Table can tell us the ionic charge of many "A" group elements.

You really do not need to memorize the most common ions since you know how to use the Octet Rule to generate these charges.

polyatomic ion

a cluster of two or more atoms covalently bonded together but possessing an overall charge; exists as a charged unit that rarely breaks apart

POLYATOMIC IONS

a unit of covalently bonded atoms carrying a net ionic charge; unit cannot be broken into simpler ions

Example #2: 2 Na + 2 H2O → 2 NaOH + H2

Note that the element hydrogen is a "formed product," so it must appear as the diatomic form. The "Na" is not one of the diatomic elements. The other two substances in the equation are compounds, so the diatomic element idea does not necessarily apply for them.

MgO is magnesium oxide

Note the cation name, then the modified name for anion ("oxygen" was truncated and "ide" added)

Table salt is named "sodium chloride." NaCL is sodium chloride

Note the cation name, then the modified name for anion.

What is the ionic charge of oxide ion?

O 2- (not +6)

ex.: CuCL vs CuCL2

different compounds must have unique names

subscript (2nd definition)

that number multiplies the preceding atom or the preceding "package" wrapped in a parentheses

Cu +2 cupric > Cu +1 cuprous

the +2 version is larger than the +1 version

Fe +3 ferric > Fe +2 ferrous

the +3 version is larger than the +2 version

name the compound CuI2

the Cu is in the Danger Zone and can exist with several possible charges; we do not YET know the charge of the Cu, but we DO know the charge of the iodide anion (using the Octet Rule); The charge of the Group VII anion of iodine is always -1; since there are TWO of these -1 anions (look at the subscript), then we have a total net charge of -2: (TWO times -1 = -2); since all ionic compounds are neutral, the Cu MUST be the +2 version! The name is copper(II) iodide. The (II) tells the reader the CHARGE of the cation is +2.

H2O

the formula for water

why we need systematic naming system

there are over 23 million compounds plus more discovered everyday

CO2 is covalent

two nonmetals

IONIC NOMENCLATURE

two part name: metal ion and nonmetal ion cation (+) anion (-)

for cation

use name of element

for anion

use name of element, cut off its "tail," then add IDE ending

NOMENCLATURE

used to provide unique names for each and every chemical

monatomic ion

when a single atom becomes an ion

examples of metals that have more than one possible charge

Fe+3 and Fe +2 Cu +2 and Cu +1

FeBr2 is named iron(II) bromide while...

FeBr3 is named iron(III) bromide

How to calculate ion charge?

Group "A" Roman Numerals indicate # of outer electrons (e-); outer electrons DO the chemistry.

the SEVEN diatomic elements

H2 N2 O2 F2 CL2 Br2 I2

Hydrogen (symbol - H) is an odd element in that it has both metal AND nonmetal properties.

Could be in Group IA or VII A on the Periodic Table

CuCL is named copper(I) chloride while...

CuCL2 is named copper(II) chloride

IDE ending usually indicates an element has become anion; not a polyatomic.

Example: N-3 nitride is NOT a polyatomic ion

different nomenclature systems in place IONIC compounds vs. COVALENT compounds

Ionic compounds have different properties than covalent compounds, so if we can identify the category of a compound just by reading its name, then we already know some of its properties.

(NH4)2S

It is easy to see that if ( ) were not used, then there would be confusion. It would then look like NH42S, and it would appear there were forty-two hydrogens! The use of ( ) is for clarity to avoid confusion.

What is the ionic charge of potassium ion?

K+1

nomen

Latin for "name"

PARENTHESES AND POLYATOMICS

Must use ( ) around the polyatomic formula when there is more than one of a particular polyatomic in formula.

H2S is covalent

NONmetal H and NONmetal S

NaCL

Na+ + CL- each is monatomic ion

NaNO3

Na+ + NO3- nitrate is polyatomic ion

WHEN do you use the diatomic form of an element?

Write diatomic form when element is a reactant or a formed product; not necessarily used when part of a compound.

Magnesium is in Group IIA. The shortest path to a Group VIIIA box is to retreat two boxes (from box 12 to box 10) to land on the neon (Ne) box.

You gave away two negative electrons, so the resulting ion has a +2 charge. You would NOT have chosen to move forward six boxes to land on the Group VIIIA argon (Ar) box! That path is the long path!

OCTET RULE

atoms tend to undergo reactions that result in an outer electron configuration of the nearest Noble Gas (8 outer e-). Exception: helium (He) is stable with just two electrons.

COVALENT (MOLECULAR) BOND

attraction through sharing of electrons (no "charges" here); occur between two NONmetals

Ba3P2

barium phosphide NOT Danger Zone (no Roman Numeral allowed!)

What holds atoms together?

bonds

CaCO3

calcium carbonate

How would you name CaS ?

calcium sulfide

SO4-2 is sulfate

cannot be broken down into S-2 and O-2

CoBr3

cobalt(III) bromide Danger Zone cation

ion

electrically charged particle resulting from loss or gain of electron(s)

IONIC BOND

electrostatic attraction of two ions due to oppositely charged particles; occur between metal and nonmetal

Diatomic Elements

elements that exist in nature as pairs - you must use a "2" subscript for these

The other part of polyatomic name comes from "central" NONmetal atom.

example: carbonate named after carbon, phosphate named after phosphorous

consider H as a NONmetal

for predicting bond types

Ca(OH)2

have more than one hydroxide; need ( )

exception to the IDE ending

hydroxide (OH-1) IS a polyatomic even though it ends in IDE

OLD SYSTEM

ic > ous cation with higher charge gets IC suffix ending

most of the diatomic elements reside ...

in either Group VIIA (the Halogens) and/or in the second period

PbS2

lead(IV) sulfide Danger Zone cation; your two sulfides summed to -4

NaCL is ionic

metal and NONmetal

PbBr2 ionic

metal and NONmetal

THE ROMAN NUMERAL INDICATES CHARGE OF CATION ...

not how many of that cation you have.

subscript (1st definition)

number written "below line" in a chemical formula

always name cation first, anion second

read left to right from the Periodic Table

Na2CrO4

sodium chromate

Most Transition Metals (B Groups) and some other metals are ...

stable at several possible cationic charges.