Chemical Nomenclature

Octet Rule Atoms tend to achieve electron configuration of Noble Gases Octet = Eight Noble Gases have eight electrons in their highest energy level General Equation for Noble Gases is S2P6

Atoms of Metallic Elements tend to lose valence electron/s, leaving an octet in the next lowest energy level Atoms of a Non-Metallic Element tend to gain a valence electron/s to achieve an Octet There are EXCEPTIONS to the Octet Rule

Diatomic Molecules These eight elements occur naturally as molecules containing two atoms. Astatine is considered a diatomic © 2009, Prentice-Hall, Inc.

Elements that exist as Diatomic Molecules Most elements, except for the noble gases, do not exist as single atoms. The halogens, along with hydrogen, nitrogen, and oxygen, exist naturally as diatomic molecules when in their element form (not as compounds). H2 F2 Cl2 Br2 I2 N2 O2 Figure 2.22

Ions Atoms or groups of atoms with a charge Cations- positive ions - get by losing electrons(s) Anions- negative ions - get by gaining electron(s) Ionic bonding- held together by the opposite charges Ionic solids are called salts

Ions Ions differ from atoms in that they have a charge; the number of electrons is either greater than, or less than, the number of protons. Cations are positively charged. They have fewer electrons than in the neutral atom. Anions are negatively charged. They have more electrons than in the neutral atom.

Ions and the Periodic Table The noble gases are the most stable (least reactive) elements on the periodic table. Their stability is associated with the number of electrons they contain. Many atoms in the main-group elements gain or lose electrons to obtain the same number of electrons as the nearest noble gas. Metals tend to lose electrons, and therefore become cations. Nonmetals tend to gain electrons, thereby becoming anions.

Even though atoms and cations have the same name, there are many chemical differences between metals and their cations. Example: Na Metal; reacts explosively in water Na Cation; quite unreactive

K+1 Ca+2 Cations Positive ions. Formed by losing electrons. More protons than electrons. Metals form cations. K+1 Has lost one electron Ca+2 Has lost two electrons

Formation of Mg2+ Cation Figure 2.14

F-1 O-2 Anion A negative ion. Has gained electrons. Non metals can gain electrons. Charge is written as a super script on the right. F-1 Has gained one electron O-2 Has gained two electrons

Formation of N3 Anion Figure 2.14

Charges on ions For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location. Elements in the same group have similar properties. Including the charge when they are ions.

Monatomic Ions- consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons Groups 1a, 2a, and 3a lose electrons and form cations Aluminum is the only common group 3a element to lose electrons and form a cation

Non-metals tend to gain electrons and form an anion. Groups 5a, 6a, and 7a form anions In group 5a, there are three non-metals which form anions N3-, P3-, & As3-

Majority of elements in 4a & 0 do not form ions Group 0 rarely forms compounds Ordinarily, two non-metals from group 4a, C & Si are found in molecular compounds

+1 +2 -3 -2 -1

Laws Conservation of Mass Law of Definite Proportion- compounds have a constant composition by mass. They react in specific ratios by mass. Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.

Law of Constant Composition Joseph Proust (1754–1826) This is also known as the law of definite proportions. It states that the elemental composition of a pure substance never varies. © 2009, Prentice-Hall, Inc.

Law of Conservation of Mass The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place. © 2009, Prentice-Hall, Inc.

Compounds Follow the Law of Definite Proportion. Have a constant composition. Have to add the same number of atoms every time. Two types.

Molecular Compounds Molecular compounds Made of molecules. Made by joining nonmetal atoms together into molecules.

Ionic Compound Ionic Compounds Made of cations and anions. Metals and nonmetals. The electrons lost by the cation are gained by the anion. The cation and anions surround each other. Smallest piece is a FORMULA UNIT.

Ionic Compounds Figure 3.8

Formula Unit Formula Unit- lowest whole-number ratio of the ions in the compound Example Na+Cl- Ratio is 1:1 The formula unit is NaCl

Formula Unit The smallest whole number ratio of atoms in an ionic compound. Ions surround each other so you can’t say which is hooked to which.

Two Types of Compounds Ionic Molecular Smallest piece Formula Unit Molecule Types of elements Metal and Nonmetal Nonmetals liquid or gas State solid Melting Point High >300ºC Low <300ºC

Ionic and Molecular Compounds

Activity: Identifying Ionic and Molecular Compounds Identify each compound as ionic or molecular. CCl4 CaF2 SF6 CuCO3 H2O

Types of Formulas Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound. © 2009, Prentice-Hall, Inc.

Writing Formulas Two sets of rules, ionic and covalent To decide which to use, decide what the first word is. If is a metal or polyatomic use ionic. If it is a non-metal use covalent

Writing Formulas Because compounds are electrically neutral, one can determine the formula of a compound this way: The charge on the cation becomes the subscript on the anion. The charge on the anion becomes the subscript on the cation. If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor. © 2009, Prentice-Hall, Inc.

Ionic Formulas Charges must add up to zero get charges from table, name of metal ion, or memorized from the list use parenthesis to indicate multiple polyatomics

Ionic Formulas Sodium nitride sodium- Na is always +1 nitride - ide tells you it comes from the table nitride is N-3

Na+1 N-3 Ionic Formulas Sodium nitride sodium- Na is always +1 nitride - ide tells you it comes from the table nitride is N-3 doesn’t add up to zero Na+1 N-3

Na3N Na+1 N-3 Ionic Formulas Sodium nitride sodium- Na is always +1 nitride - ide tells you it comes from the table nitride is N-3 doesn’t add up to zero Need 3 Na Na3N Na+1 N-3

Writing Formulas Write the formula for calcium chloride. Calcium is Ca+2 Chloride is Cl-1 Ca+2 Cl-1 would have a +1 charge. Need another Cl-1 Ca+2 Cl2-1

Crisscross Switch the numerical value of the charges Ba2+ N3- 2 3 Ba3 N2 Reduce ratio if possible

Polyatomic Ions Polyatomic Ion- Tightly bound groups of atoms that behave as a unit and carry a charge Unlike monatomic ions; Sulfate anion is composed of 1 Sulfur atom and 4 oxygen atoms These five atoms form a Sulfate Anion It has a –2 charge an is written SO42-

Polyatomic Ions A polyatomic ion consists of a group of atoms with an overall net charge. These two are also called oxoanions because they contain oxygen attached to some other element. The most common polyatomic cation is NH4+. Figure 3.14

Polyatomic anions either end in ITE or ATE Out of the two similar polyatomic ions, the polyatomic with less Oxygens ends in ite Example: Sulfite and Sulfate Sulfite; SO32- Sulfate; SO42-

There are three exceptions to the Polyatomic Rule 1) Ammonium NH4+ ---- The only positive polyatomic ion 2) Cyanide CN- ---- Ends in IDE 3) Hydroxide OH- --- Ends in IDE

Write the formulas for these Lithium sulfide tin (II) oxide tin (IV) oxide Magnesium fluoride Copper (II) sulfate Iron (III) phosphide gallium nitrate Iron (III) sulfide

Ionic Compounds Sodium sulfite calcium iodide Lead (II) oxide Lead (IV) oxide Mercury (I) sulfide Barium chromate Aluminum hydrogen sulfate Cerium (IV) nitrite

Write the formulas for these Ammonium chloride ammonium sulfide barium nitrate

Naming compounds Two types Ionic - metal and non metal or polyatomics Covalent- we will just learn the rules for 2 non-metals

There are two methods for naming cations with multiple charges The Stock System and Classical System The Stock system is the preferred method

Stock System The stock system uses roman numerals in ( ). The ( ) indicate the numerical charge of the cation. Example: Fe2+ Name: Iron(II) There is no space between the name and the parenthesis Cu1+ Name: Copper(1)

Classical System The classical system uses the root word with different suffixes as the end of the word OUS- is used to name the cation with the lower of the two ionic charges IC- is used to name the cation with the higher of the two ionic charges

Example: Fe2+ and Fe3+ Name: Ferrous Name: Ferric What is the problem with the classical system?

The classical system does not tell you the charge of the ion. The name only tells you which cation is either larger or smaller out of the pair

Few transition metals have only one ionic charge These three elements don’t have roman numerals next to there name Exceptions: Ag+ Cd2+ Zn2+

Ionic compounds If the cation is monoatomic- Name the metal (cation) just write the name. If the cation is polyatomic- name it If the anion is monoatomic- name it but change the ending to -ide If the anion is poly atomic- just name it practice

Naming Binary Ionic Compounds Write the name of CuO Need the charge of Cu O is -2 copper must be +2 Copper (II) chloride Name CoCl3 Cl is -1 and there are three of them = -3 Co must be +3 Cobalt (III) chloride

Naming Binary Ionic Compounds Write the name of Cu2S. Since S is -2, the Cu2 must be +2, so each one is +1. copper (I) sulfide Fe2O3 Each O is -2 3 x -2 = -6 3 Fe must = +6, so each is +2. iron (III) oxide

Ternary Ionic Compounds Will have polyatomic ions At least three elements (3 capital letters) Still just name the ions NaNO3 CaSO4 CuSO3

Ternary Ionic Compounds LiCN Fe(OH)3 (NH4)2CO3 NiPO4

Ionic Compounds Have to know what ions they form off table, polyatomic, or figure it out CaS K2S AlPO4 K2SO4 FeS CoI3

Ionic Compounds Fe2(C2O4) MgO MnO KMnO4 NH4NO3 Hg2Cl2 Cr2O3

Ionic Compounds KClO4 NaClO3 YBrO2 Cr(ClO)6

Writing names and Formulas Molecular Compounds Writing names and Formulas

Molecules & Molecular Compounds Elements are the building materials of the substances that make up all living and nonliving things Only about 100 elements but there are millions of different compounds made from their atoms Thus, naming compounds is an essential skill in chemistry

In nature, only Noble Gases tend to exist as isolated atoms. They are monatomic; that is, they consist of single atoms Many elements found in nature are in the form of molecules Molecule- is the smallest electrically neutral unit of a substance that still has the properties of the substance Molecules are made up of two or more atoms that act as a unit

Atoms of different elements may combine chemically to form compounds In many compounds, the atoms combine to form molecules. Molecular Compounds- Compounds composed of molecules Molecular Compounds tend to have relativity low melting and boiling points Many of these compounds thus exist as gases or liquids at room temperature.

Molecular compounds made of just nonmetals smallest piece is a molecule can’t be held together because of opposite charges. can’t use charges to figure out how many of each atom

Naming Covalent Compounds Two words, with prefixes Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, septa, nona, deca First element whole name with the appropriate prefix, except mono Second element, -ide ending with appropriate prefix Practice

Nomenclature of Binary Compounds The less electronegative atom is usually listed first. A prefix is used to denote the number of atoms of each element in the compound (mono- is not used on the first element listed, however) . © 2009, Prentice-Hall, Inc.

Nomenclature of Binary Compounds The ending on the more electronegative element is changed to -ide. CO2: carbon dioxide CCl4: carbon tetrachloride © 2009, Prentice-Hall, Inc.

Nomenclature of Binary Compounds If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one. N2O5: dinitrogen pentoxide © 2009, Prentice-Hall, Inc.

Naming Covalent Compounds CCl4 N2O4 XeF6 N4O4 P2O10

Name These N2O NO2 Cl2O7 CBr4 CO2 BaCl2

Covalent compounds The name tells you how to write the formula duh Sulfur dioxide diflourine monoxide nitrogen trichloride diphosphorus pentoxide

Write formulas for these diphosphorus pentoxide tetraiodide nonoxide sulfur hexaflouride nitrogen trioxide Carbon tetrahydride phosphorus trifluoride aluminum chloride

More Names and formulas

Acids Substances that produce H+ ions when dissolved in water All acids begin with H Two types of acids Oxyacids non oxyacids

Naming acids If the formula has oxygen in it write the name of the anion, but change ate to -ic acid ite to -ous acid Watch out for sulfuric and sulfurous H2CrO4 HMnO4 HNO2

Naming acids If the acid doesn’t have oxygen add the prefix hydro- change the suffix -ide to -ic acid HCl H2S HCN

Formulas for acids Backwards from names If it has hydro- in the name it has no oxygen anion ends in -ide No hydro, anion ends in -ate or -ite Write anion and add enough H to balance the charges.

Formulas for acids hydrofluoric acid dichromic acid carbonic acid hydrophosphoric acid hypofluorous acid perchloric acid phosphorous acid

Hydrates Some salts trap water crystals when they form crystals these are hydrates. Both the name and the formula needs to indicate how many water molecules are trapped In the name we add the word hydrate with a prefix that tells us how many water molecules

Hydrates In the formula you put a dot and then write the number of molecules. Calcium chloride dihydrate = CaCl2·2H2O Chromium (III) nitrate hexahydrate = Cr(NO3)3· 6H2O