A2.2- Naming Ionic and Molecular Compounds

introduction

Ionic compounds are composed of metals and non-metals whereas, molecular (covalent) compounds are composed of just non-metals. In this section, you will look at how to name and form both ionic and molecular compounds and the properties of of both.

Read pages 40-41, be sure to make note of the Figure A2.15, A2.16, and A2.17.

Define the following terms:

crystal lattice
formula unit
ionic bonding

Common names for some ionic compounds

Copy Table A2.2 into your Science notebook. You will be expected to know some of these common names for ionic compounds

ionic compounds

Pages 40-41

Ionic compounds consist of a metal and a nonmetal
Common properties of ionic compounds:
Solid at room temperature
Have the tendency to dissolve in water
Solutions of ionic compounds always conduct electricity – conductors

ionic bonds

Ionic compounds are formed by atoms stealing electrons to obtain a full valence orbital

Example:

•NaCl

CaO

naming ionic compouns

All names of ionic compounds have two parts, because all ionic compounds are made from two parts. Every ionic compound is made up of a cation (positive) and an anion (negative).

Naming rules:

Name the cation first by using the element's name (It is usually a metal ion)
Name the anion second by using the first part of the element's name and changin the last part to "-ide" (The anion is usually a non-metal)

FORMULAS FOR IONIC COMPOUNDS and the method of lowest common multiple

learning activities

Read Pages 42-43 carefully, make notes, review Example Problem A2.1 and complete practice problems on page 43

Multivalent elements

Read page 44 and note the InfoBit at the top of the page

Ionic compounds can contain multivalent metals

Multivalent elements: elements with more than one stable ion

- Iron
- Lead

Examples:

NiCl_{2 (s)}Nickel (II) chloride
PdBr_{3 (s)} Palladium (III) bromide
PtS_{2 (s)}Platinum (IV) sulfide

learning activity

Go through the Example Problem A2.2 and then attempt the Practice Problem #2 on page 44.

polyatomic ions

Read the bottom of page 44 up to and including the first paragraph on page 46. Pay special attention to Table A2.7 on page 45.

Polyatomic Ions: ions that are made up of several non-metallic atoms

Sulfate
Sulfite
Hydroxide

learning activity

Carefully go over the Example Problems A2.3 and A2.4 on page 46
Do the Practice Problems on page 46. Again, if you are having difficulty, see a teacher for assistance (as often as you need!)

What are Molecular Compounds??

Continue to read the bottom of page 46 – Molecular Compounds – and 47. Pay special attention to the diagrams (Figures A2.20, A2.21, and A2.3) showing the formation of covalent bonds in molecular substances.

Finish reading about binary molecular compounds and compounds that contain hydrogen on pages 48-49.

Define in your Science notebook:

molecule
covalent bonds
molecular element
diatomic

Copy into your Science notebook:

Table A2.8 You will be expected to know some common names for molecular compounds.
Table A2.9 This is very important!
Table A2.10 Key to naming and writing formulas for molecular compounds.
Table A2.12 MEMORIZE! (Hydrogen is a special element with unique properties so hydrogen containing compounds are named differently)

molecular compounds

Page 40-41

A molecule forms when two or more non-metallic atoms bond to the same element (ie. CO₂, H₂O)

Properties of molecular compounds:

Solid, liquid or gas
Poor conductors
Don’t dissolve in water very well

covalent bonds

Molecular compounds are formed by atoms sharing electrons to obtain a full valence orbital

Example:

•Cl₂

•CO₂

Naming molecular compounds

Molecules that DO NOT contain hydrogen:

Steps:

1) Name the first element

2) Name the second element with “-ide” at the end

3) Add prefixes indicating numbers of atoms

learning activities

Go over Example Problem A2.5 and do Practice Question #5 on page 49
As a review of Ionic & Molecular Compounds, answer questions #1 - 12 from the Check and Reflect on page 50. For questions that have more than one letter, do every other letter.
If you need more practice, do the rest of the Check and Reflect questions on page 50.

Next: You are now ready to move on to complete Section A2.3

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