Elements and Polyatomic Ions

Chapter 7 Section 1.2 & 2: Naming Binary Molecular Compounds

Fill in the Blank

review: When group 1 elements become ions, what charge do they have?

Multiple Choice

What ending is used for negative anions

• -ide

• -ite

• -ion

• -ex

Fill in the Blank

Give the name for the monoatomic ion Cl-

​​Stock-System

​​For d-block elements that form multiple anions, roman numerals that tell the charge are used to distinguish them

• ​Cu⁺ = Copper(I)

• ​Cu²⁺ = Copper(II)

• ​These numerals are used in the names of compounds

  • ​CuCl₂ = Copper(II) Chloride

Fill in the Blank

What is the charge of the ion Iron (III)

​​Compounds containing Polyatomic Ions

• ​​Most polyatomic ions are negatively charged

• Most polyatomic ions are oxyanions

  • ​contain oxygen

  • ​Some elements can form with oxygen in multiple ways to form different ions

    • ​The one with the greater number of oxygen atoms = -ate

    • ​smaller number of oxygen atoms = -ite

​​​Compounds containing Polyatomic Ions

• ​Some elements form more than two oxyanions

  • ​Oxyanion less than -ite ion has the prefix hypo-

  • ​Oxyanion greater than -ate has the prefix per-​

​​Compounds containing Polyatomic ions

​​Compounds with polyatomic ions are named the same way as monoatomic ions

• ​Cation name first, then the anion name

  • ​AgNO₄= Silver Nitrate

  • ​AgNO₃=Silver Nitrite

• ​If multiples of a polyatomic ion are present, the ion is in parenthesis in the formula

  • ​Aluminum Sulfate = Al₂(SO₄)₂

Multiple Choice

These polyatomic ions contain oxygen

• oxyanions

• oxites

• oxates

Multiple Choice

Which Polyatomic ion has the most oxygen atoms

• hypochlorite

• chlorite

• chlorate

• perchlorate

​Naming Binary Molecular Compounds

• ​Molecular compounds are composed of individual covalently bonded units

• ​Two methods are used to name them

  • ​Old method uses prefixes

  • ​Stock System using oxidation numbers

​Naming using Prefixes

• ​Prefix before an element name tells you how many there are

  • ​CO = Carbon Monoxide

  • ​CCl₄= Carbon Tetrachloride

  • ​N₂O= Dinitrogen monoxide

  • ​N₂O₃= Dinitrogen Trioxide

​Rules for naming Molecular Compounds

• ​​Rules to follow

  • ​The element with the lower group number comes first, if in the same group, the larger period number is first

    • Add a prefix if the first element has more than one atom

  • ​The second element is named by

    • combining a prefix indicating the number of atoms contributed by the element,

    • the root of the name of the element

    • ​the ending -ide

  • Drop the "o" or "a" in the prefix the beginning if the next ​letter would be a vowel

    • ​Monoxide

  • ​In general element order is: C, P, N, H, S, I, Br, Cl, O, F

Fill in the Blank

Name the binary molecular compound: SO₃

Fill in the Blank

Name the Binary Molecular compound ICl₃

Fill in the Blank

Name the Binary molecular compound PBr₅

​Acids & Salts

• Acid refers to the compound in an aqueous solution​

• There are different types of acids

  • ​Binary acids= consist of two elements

    • ​usually Hydrogen and a halogen

  • ​Oxyacids= Consist of hydrogen, oxygen, and one other element

    • ​Many polyatomic ions are produced by the loss of hydrogen ions from oxyacids

• ​Salt: an ionic compound composed of a cation and the anion from an acid

  • ​Some salts contain more than one hydrogen atom, they have "hydrogen" or "Bi-" added to their name

Multiple Choice

"An ionic compound composed of a cation and the anion from an acid "is known as what?

• An Acid product

• a Salt

• A Base

​Section 2: Oxidation Numbers

• ​Oxidation Numbers/States: Indicate the general distribution of electrons among the bonding atoms in a molecular compound/polyatomic ion

  • ​Can be quite arbitrary

  • ​help in naming compounds and balancing equations

​Rules for Assigning Oxidation Numbers

• ​The atoms in a pure element have an oxidation number of 0

  • ​Na₂ has an oxidation of 0

• ​The more electronegative element in a binary compound is the same as it would be as an anion and same for the cation/less electronegative element

• ​Fluorine always has a -1 number

• ​Oxygen has an oxidation number of -2 in almost all compounds

  • exceptions are peroxides (-1) and when combined with F (+2)

• ​Hydrogen has a +1 in all more electronegative elements and a -1 charge when with metals

• Sum of oxidation numbers in a neutral compound is 0

• Sum of oxidation numbers in polyatomic ions is equal to the charge

  • All rules above apply to ionic compounds as well

​Using Oxidation Numbers for formula names

• ​Many nonmetals can have more than one oxidation number

  • ​Table six on page 235

• ​Using oxidation numbers and the Stock System of naming allows us to be more specific about an compound

• ​Oxidation numbers are the basis for the roman numeral system for naming compounds

  Oxidation numbers can give predictions of possible combinations of atoms

  Known oxidation numbers can lead to the discovery of unknown numbers

​How to even use this

• ​Always start with the oxidation number that you know and work backwards.

• ​On the board Practice: Pages 233 & 234