Lesson 10: Types of Chemicals (Objectives 1-4)
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 | Objective 2 | Objective 3 | Objective 4
Objective 1. From the name of a chemical, 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. We will not be dealing with alloys in this particular lesson.
Exercises
Which of the following chemicals are elements and which are compounds?
a. water
b. ammonia
c. oxygen
d. sulfur
e. carbon dioxide
f. copper(II) sulfate
g. ferrous oxide
Worked-Out Examples (a,b,c)
(a) Water: Water is one of those things that you should just recognize by name and recognize that it consists of hydrogen and oxygen and therefore water is a compound.
(b) Ammonia: Ammonia also is a name of a chemical which is a compound that you should recognize, rather than analyze. Ammonia consists of nitrogen and hydrogen; its formula is NH3. So, ammonia is a compound.
(c) Oxygen: Oxygen you should recognize as an element, not as a compound.
With those three worked out as examples, try doing the rest of exercise 1. When you have completed that, check your answers below.
Answers to Exercises
Which of the following chemicals are elements and which are compounds?
a. water - compound
b. ammonia - compound
c. oxygen - element
d. sulfur - element
e. carbon dioxide - compound
f. copper(II) sulfate - compound
g. ferrous oxide - compound
Objective 2. From the name of an element, determine whether it is a metal, a nonmetal or an inert gas.
The second objective says that from the name of an element you should be able to determine whether it is a metal, nonmetal or an inert gas. To do that, you either have to rely on your recognition of these things, or consult a periodic table. 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 and also hydrogen with the exception of the last group of elements on the periodic table, which are the inert gases.
Exercises
Which of the following elements are metals, which are nonmetals and which are inert gases?
a. phosphorus
b. helium
c. hydrogen
d. magnesium
e. manganese
f. argon
g. lead
Worked-Out Examples (a,b,c)
(a) Phosphorus: Because it is over toward the right side of the periodic table, phosphorus, with the symbol P, is a nonmetal.
(b) Helium: Helium, with the symbol He, is an inert gas.
(c) Hydrogen: Although it is way over on the left side of the periodic table, hydrogen should be recognized by you as being a nonmetal.
Answers to Exercises
Which of the following elements are metals, which are nonmetals and which are inert gases?
a. phosphorus - nonmetal
b. helium - inert gas
c. hydrogen - nonmetal
d. magnesium - metal
e. manganese - metal
f. argon - inert gas
g. lead - metal
Objective 3. From the name of an element, determine whether it has metallic or covalent 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. This time I will just let you work through all of the questions in exercise 3.
Exercises
Which of the following elements have metallic bonding and which have covalent bonding?
a. calcium
b. cobalt
c. copper
d. chlorine
e. beryllium
f. boron
g. bromine
Answers to Exercises
Which of the following elements have metallic bonding and which have covalent bonding?
a. calcium - metallic
b. cobalt - metallic
c. copper - metallic
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.
With that in mind, work through exercise 4.
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 to Exercises
Which of the following elements are network materials and which are molecular materials?
a. zinc - network
b. aluminum - network
c. silicon - network
d. carbon - network
e. nitrogen - molecular
f. oxygen - molecular
g. chlorine - molecular