Unit 2 – Notes 2B “Nomenclature” Naming Ionic Compounds

In this unit you will learn about a type of substance called an “ionic compound”. An ionic compound forms when a metallic element and a non-metallic element combine. What happens is this: Atoms of the metallic element lose electrons to form positively-charged ions called “cations”. A positive charge is shown as a + or as a number followed by a +. Ex: Na + Ca 2+, Al 3+

Atoms of the non-metallic element gain electrons to form negatively-charged ions called “anions”. A negative charge is shown as a - or as a number followed by a -. Ex: F - S 2-, N 3-

An ion may form after several non-metal atom joins together with other nonmetal atoms. This entire group of atoms is called a “polyatomic ion”. Your orange sheet contains a list of the common polyatomic ions. It includes one cation and many anions. Each of these ions has a distinct name and a distinct charge. EX: NH 4 + is called the “ammonium” ion and CO 3 2- is called the “carbonate” ion

The oppositely-charged ions combine in a manner so that overall the entire ionic compound becomes “neutral”: The sum of the charges of all the ions present in the compound equals 0. You are learning how to create neutral formulas for ionic compounds in class. This video explains how to name ionic compounds.

Naming binary ionic compounds. Naming binary ionic compounds. A binary ionic compound contains ions from only 2 different elements: a metallic element and a non-metallic element. The metallic element (the cation) will always be found first in a binary ionic compound’s chemical formula, and the non-metallic element (the anion) will always be found second. When you name an ionic compound, you just say the cation’s name followed by the anion’s name.

The cation’s name in a binary ionic compound may be identical to the name of the element it came from, (as written in the element’s square on the periodic table). The cation’s name in a binary ionic compound may be identical to the name of the element it came from, (as written in the element’s square on the periodic table). This occurs when an element is known to only form cations that have one particular positive charge. We’ll look at column 1 metals as an example.

Metals in column 1 only form 1+ cations; so a column 1 cation is called by the same name as the element it formed from. Metals in column 1 only form 1+ cations; so a column 1 cation is called by the same name as the element it formed from. Ex: Na + is called the sodium ion. Li + is called the lithium ion. K + is called the potassium ion. Etc. Although hydrogen is not a metal, it is still able to form a cation with only one particular positive charge! So, H + is called the hydrogen ion. Although hydrogen is not a metal, it is still able to form a cation with only one particular positive charge! So, H + is called the hydrogen ion. Note: Hydrogen is a non-metal, and when it behaves similarly to other non-metals, it forms a 1 - anion. H - is called the “hydride” ion. You should memorize this name!

If a metallic element is known to form cations whose positive charge is variable, it is then necessary to specify the charge as a part of the cation’s name. If a metallic element is known to form cations whose positive charge is variable, it is then necessary to specify the charge as a part of the cation’s name. One method is to use a Roman numeral. This method of nomenclature is known as the “Stock” system. Copper ions that have a 1 + charge are called “copper(I) ions”. Copper ions that have a 2 + charge are called “copper(II) ions. It is necessary to memorize the Roman numerals in order to name compounds by their Stock name. 1 = I 2 = II 3 = III 4 = IV 5 = V 6 = VI 7 = VII

An alternate method, called the “classical” method, may be used when metals are known to form 2 common positively-charged ions. An alternate method, called the “classical” method, may be used when metals are known to form 2 common positively-charged ions. The root of the element’s name comes first and is followed by one of 2 suffixes. Latin names are used when the element symbols on the periodic table are derived from the element’s latin name. -ous is added to indicate the lesser of 2 possible charges. -ic is added to indicate the higher of 2 possible charges. Cu + is referred to by the Stock name, copper(I); and it is referred to by the classical name, cuprous Cu + is referred to by the Stock name, copper(I); and it is referred to by the classical name, cuprous Cu 2+ is similarly either referred to as copper(II) or cupric Cu 2+ is similarly either referred to as copper(II) or cupric

Cations that have 2 variable positive charges and are named in Latin. Cations that have 2 variable positive charges and are named in Latin. Cu CuprumCuprousCupric Cu CuprumCuprousCupric FeFerrumFerrousFerric FeFerrumFerrousFerric SnStannumStannousStannic SnStannumStannousStannic AuAurumAurousAuric AuAurumAurousAuric Hg Hydrargyrum Hydrargyrous Hydrargyric Hg Hydrargyrum Hydrargyrous Hydrargyric PbPlumbumPlumbousPlumbic PbPlumbumPlumbousPlumbic

Naming anions. Naming anions. In a binary ionic compound, the anion’s name will be SIMILAR (although not identical) to the name of the non-metallic element it came from. An anion from a nonmetallic element is named by adding the suffix –ide to the “root” of the element’s name. These are the anion names you should memorize from columns 15, 16, and 17: These are the anion names you should memorize from columns 15, 16, and 17: Nitride, phosphide, arsenide Nitride, phosphide, arsenide Oxide, sulfide, selenide, telluride Oxide, sulfide, selenide, telluride Fluoride, chloride, bromide, iodide, astatide Fluoride, chloride, bromide, iodide, astatide Column 1: hydrogen’s anion, H - = hydride. Column 1: hydrogen’s anion, H - = hydride.

When you name an ionic compound, you just say the cation’s name followed by the anion’s name. When you name an ionic compound, you just say the cation’s name followed by the anion’s name. NaCl = sodium chloride LiO = lithiun oxide Ca 3 S 2 = calcium sulfide Ba(C 2 H 3 O 2 ) 2 = barium acetate (NH 4 ) 2 (SO 4 ) = ammonium sulfate This is more correctly written as (NH 4 ) 2 SO 4 Notice the “numbers” aren’t part of the names Notice the “numbers” aren’t part of the names

Whenever the cation is known to exist with a variable charge, the specific cation should be indicated as you name the compound. This is by either using the Stock name or the classical name. Whenever the cation is known to exist with a variable charge, the specific cation should be indicated as you name the compound. This is by either using the Stock name or the classical name. CuCl = copper(I) chloride or cuprous chloride CuO = copper(II) oxide or cupric oxide Fe 2 S 3 = iron(III) sulfide or ferric sulfide Fe(C 2 H 3 O 2 ) 2 = iron(II) acetate or ferrous acetate Notice that the Roman numerals aren’t gotten directly from the presence of subscripts. Notice that the Roman numerals aren’t gotten directly from the presence of subscripts.