Types of Substances

The first seven objectives for this lesson deal with identifying various types or classifications of chemicals. These range from the simple awareness of whether you are dealing with an element or a compound to determining whether a compound exists as a network or as molecules.

Objective 1: From the name of a substance, determine whether it is an element or compound

The first objective says that from the name of the chemical you should be able to determine whether it is an element or a compound. Doing that essentially involves recognizing the names of the elements, and then if you are dealing with something that combines more than one elements, then you are dealing with a compound.

*Note: we are ignoring mixtures here.

Exercises

Which of the following substances are elements and which are compounds?

a. water

b. iron (II) oxide

c. sulfur

d. carbon dioxide

e. copper(II) sulfate

f. oxygen

Answers

a. compound

b. compound

c. element

d. compound

e. compound

f. element

Objective 2: From the name of an element, determine whether it is a metal or a nonmetal

The elements which are found on the left side up to the diagonal line that includes aluminum are going to be the metals. The nonmetals will include the other elements up and to the right of that diagonal line, plus hydrogen.

Exercises

Which of the following elements are metals and which are nonmetals? Identify any noble gases as such.

a. phosphorus

b. helium

c. hydrogen

d. magnesium

e. manganese

f. argon

g. lead

Answers

a. nonmetal

b. nonmetal (noble gas)

c. nonmetal

d. metal

e. metal

f. nonmetal (noble gas)

g. metal

Objective 3: From the name of an element, determine whether it has metallic or covalent bonding, or no bonding

In order to do this, you have to decide whether the element that you are dealing with is a metal or a nonmetal, the same kind of thing that we just did in the previous example. If the element is a noble gas, then it has no bonding. Otherwise, all non-metals have covalent bonding.

Exercises

Which of the following elements have metallic bonding and which have covalent bonding?

a. calcium

b. cobalt

c. krypton

d. chlorine

e. beryllium

f. boron

g. bromine

Answers

a. calcium - metallic

b. cobalt - metallic

c. krypton - none

d. chlorine - covalent

e. beryllium - metallic

f. boron - covalent

g. bromine - covalent

Objective 4: From the name of an element, determine whether it is a network or molecular material

The fourth objective says that from the name of an element, determine whether it is a network or molecular material. The guidelines for this go back to when we were working with bonding, and here's what you have to do for an element. Elements will either have metallic or covalent bonding. If the element has metallic bonding, it will be a network material. If the element has covalent bonding, then it might be network, it might be molecular. Most covalently bonded materials are molecular materials. The exceptions that we will deal with in this course are: boron, carbon, silicon and silicon dioxide. So as far as elements are concerned, boron, carbon and silicon are the exceptions that you have to worry about.

Exercises

Which of the following elements are network materials and which are molecular materials?

a. zinc

b. aluminum

c. silicon

d. carbon

e. nitrogen

f. oxygen

g. chlorine

Answers

a. zinc - network

b. aluminum - network

c. silicon - network

d. carbon - network

e. nitrogen - molecular

f. oxygen - molecular

g. chlorine - molecular

Objective 5: From the name of a compound, determine whether it is ionic or covalent.

There is more than one step to this process. From the name of the compound, you have to be able to figure out whether you have metal and nonmetal combined with one another, in which case you would have an ionic material, or whether you have only nonmetals, in which case you generally have covalent bonding. The one exception to this rule involves the ammonium ion (NH₄⁺) which contains only nonmetals but allows for ionic bonding.

Exercises

Which of the following compounds are ionic and which are covalent?

a. manganese(IV) sulfide

b. selenium dioxide

c. ammonium nitrate

d. potassium sulfide

e. carbon disulfide

f. water

g. carbon tetrachloride

Answers

a. manganese(IV) sulfide - ionic

b. selenium dioxide - covalent

c. ammonium nitrate - ionic

d. potassium sulfide - ionic

e. carbon disulfide - covalent

f. water - covalent

g. carbon tetrachloride - covalent

Objective 6: From the name of a compound, determine whether it is network or molecular.

Again, the guideline for this is dependent on what kind of bonding you have. In a compound, you will either have ionic bonding or covalent bonding. If you have ionic bonding, you will be dealing with a network material. On the other hand, if you have covalent bonding, you will probably have a molecular material. The exceptions, again, are boron, carbon, silicon and silicon dioxide. Other covalent materials (at least the ones we deal with in this course) will be molecular.

Exercises

Which of the following compounds are network materials and which are molecular materials?

a. carbon dioxide

b. silicon dioxide

c. nitrogen dioxide

d. sodium chloride

e. hydrogen sulfide

f. iron (II) bromide

g. water

Answers

a. carbon dioxide - molecular

b. silicon dioxide - network

c. nitrogen dioxide - molecular

d. sodium chloride - network

e. hydrogen sulfide - molecular

f. iron (II) bromide - network

g. water - molecular