chapter 3

Chapter 3Elements Combine to Form Compounds

Name the Super – Heroes

Compound – “Pun”

Compound - “Pun”

Compounds ( 2nd type of Pure Substance)Compound: a pure substance made up of

more than one kind of element in which the atoms

of the elements are joined together.

Compounds form through chemical bonds: these are links between two or more atoms that

hold the atoms together

Two types of Compounds (chemical bonds)Ionic Compounds Molecular (covalent) Compounds

Compounds…Compounds are represented by a combination of

element symbols known as a chemical formula:

Chemical Formula (tells us):type of elements (atoms) proportion (number) of each atom involved

Elements Present Proportion: (# of each element) CH4 Carbon and Hydrogen 1 carbon atom and 4 hydrogen

atoms

NaCl Sodium and Chlorine 1 sodium atom and 1 chlorine atom

Two types of compounds

Molecular (covalent) compounds:

formed between non- metals only

this type of bonding involves sharing of electrons

Examples: (we need to know) 1) Carbon Dioxide (gas) - CO2 2) Water - H2O 3) Sucrose (table sugar) – C12H22O11

4) Methane (gas) – CH4

Ionic Compounds

formed between metals and non-metals.

this type of bonding involves atoms attracting to each other because of opposite charges (+) (-)

the atoms involved either gain or loose electrons to form charged particles called Ions (positive or negative)

Examples: (we need to know) 1) Sodium Chloride (salt) - NaCl 2) Calcium Carbonate (chalk) - CaCO3 3) Sodium Sulfate (salt) - Na2SO4 4) Sodium Hydroxide (drain cleaner) –

NaOH

Molecular (Covalent) “share”

Ionic “give away and “charge”

Ionic Compounds - “Ions”

Counting Atoms Chemical Formula

Elements Involved

Number of Atoms

CO2 Carbon (C) Oxygen (O)

3 atoms - 1 carbon (C) - 2 oxygen (O)

MgCl Magnesium (Mg)Chlorine (Cl)

2 atoms - 1 magnesium (Mg) - 1 chlorine (Cl)

Na2SO4 Sodium (Na) Sulphur (S)Oxygen (O)

7 atoms - 2 Sodium (Na) - 1 Sulphur (S) - 4 Oxygen (O)

C12H22O11 Carbon (C) Hydrogen (H)Oxygen (O)

??? atoms – ___ carbon (C) ___ hydrogen (H) ___ oxygen (O)

Chemical Formulas

Chemical Names of Compounds

When given a chemical formula, you can write the chemical name which indicates the elements present in the compound

IUPAC (International Union of Pure and Applied Chemistry)a group that represent chemists around the

world and is responsible for the rules when naming compounds.

Ionic and Molecular compounds have their own set of rules to follow.

Naming CompoundsSet of rules that you have to follow when

writing the names for Ionic and Molecular Compounds.

Basic steps:determine the elements involved in the

chemical formula (compound)…. Metals and Non- Metals

determine the type of compound (Ionic or Molecular)

follow the rules outline for Ionic or Molecular

Naming Ionic Compoundsformed between metals and non-metals.

Rules: 1) Name the first element (atom)

2) Name second element by ending the name with the suffix “ide”

3) Put the two names together

Example of a Ionic CompoundExample : name for the compound NaCl

Na (sodium) - metal Cl (chlorine) - non- metal

Name: Sodium chloride

Naming Molecular (covalent) Compoundsformed between non-metals.

numbers (subscripts) are important and have to be used at the beginning of each element in the naming of the compound. ……(see page 83)

Rules: 1) Name the first element (atom) 2) Name second element by ending the name with the suffix “ide”

3) Add the “prefix” to the element names to show the number of atoms in the compound

Example of a Molecular (covalent) CompoundExample : name for the compound CO2

C (carbon) - non-metal O (oxygen) – non- metal

CO2 [Have to use Prefix to show number of atoms in compound]

Name : Carbon dioxide

Prefixes (table 3.4, page 83) Number of atoms Prefix

1 Mono (used only for the second atom)

2 di

3 tri

4 tetra

5 penta

6 hexa

7 hepta

8 octa

9 nona

10 deca

Name the following compounds Mg3P2 Mg (metal) P (non –metal) ….. Ionic Magnesium Phosphorus

Numbers are NOT important …

Name: Magnesium phosphide

Name the following CompoundN2O3

N (non-metal) O (non-metal) …..Molecular (Covalent) Nitrogen Oxygen

Numbers are important

N2O3Name : Dinitrogen trioxide

Try These ???1) Ag3N -

2) CCl4 -

Physical ChangesPhysical Change

a change in matter in which NO new substances are produced

the appearance of a substance may be changed but the bonds between the particles (atoms) have not broken

atoms either move closer together or farther apart

Examples - change of state [freezing, melting …] - dissolving [sugar in water] - cutting paper

Chemical ChangesChemical Change

a change in matter in which NEW substances are produced with NEW properties.

Clues that May Indicate a Chemical ChangeA new color appearsHeat or light is given off during the changeBubbles or gas are formedSolid clumps (precipitate) forms in the liquidThe change is difficult to reverse

Examples: - Corrosion [metals rusting] - Combustion [burning] - Fruit Ripening

Chemical Changes and Chemical ReactionsChemical Changes also referred to a Chemical

Reaction

In every chemical reaction there is something used up and something produced (made)

Reactants ProductsMagnesium + Hydrochloric Acid → Hydrogen + Magnesium

Chloride

Sodium + Chlorine ------------------→ Sodium Chloride

The END !!!!!