It is easy to describe elements and mixtures. But how are compounds named? In the example of iron sulphide that was used earlier, which element is named first, and which 'ending' is given to the compound name (in this case, the ending is -ide)?
The following are some guidelines for naming compounds:
The compound name will always include the
names of the elements that are part of it.
A compound of
iron (Fe) and
sulphur (S) is
ironsulph ide (FeS)
A compound of
potassium (K) and
bromine (Br) is
potassiumbrom ide (KBr)
A compound of
sodium (Na) and
chlorine (Cl) is
sodiumchlor ide (NaCl)
In a compound, the element that is on the left of the Periodic Table, is used
first when naming the compound. In the example of NaCl, sodium is a group 1 element on the left hand side of the table, while chlorine is in group 7 on the right of the table. Sodium therefore comes first in the compound name. The same is true for FeS and KBr.
The
symbols of the elements can be used to represent compounds e.g. FeS, NaCl, KBr and H
2 O. These are called
chemical formulae . In the first three examples, the ratio of the elements in each compound is 1:1. So, for FeS, there is one atom of iron for every atom of sulphur in the compound. In the last example (H
2 O) there are two atoms of hydrogen for every atom of oxygen in the compound.
A compound may contain
compound ions . An ion is an atom that has lost (positive ion) or gained (negative ion) electrons. Some of the more common compound ions and their formulae are given below.
Name of compound ion
Formula
Carbonate
CO
32
Sulphate
SO
42
Hydroxide
OH
Ammonium
NH
4+
Nitrate
NO
3
Hydrogen carbonate
HCO
3
Phosphate
PO
43
Chlorate
ClO
3
Cyanide
CN
Chromate
CrO
42
Permanganate
MnO
4
When there are only two elements in the compound, the compound is often given a
suffix (ending) of -ide. You would have seen this in some of the examples we have used so far. For compound ions, when a non-metal is combined with oxygen to form a negative ion (anion) which then combines with a positive ion (cation) from hydrogen or a metal, then the suffix of the name will be ...ate or ...ite. NO
3 for example, is a negative ion, which may combine with a cation such as hydrogen (HNO
3 ) or a metal like potassium (KNO
3 ). The NO
3 anion has the name nitr
ate . SO
32
in a formula is sulph
ite , e.g. sodium sulphite (Na
2 SO
3 ).
SO
42
is sulph
ate and PO
43
is phosph
ate .
Prefixes can be used to describe the ratio of the elements that are in the compound. You should know the following prefixes: 'mono' (one), 'di' (two) and 'tri' (three).
CO (carbon monoxide) - There is one atom of oxygen for every one atom of carbon
NO
2 (nitrogen dioxide) - There are two atoms of oxygen for every one atom of nitrogen
SO
3 (sulphur trioxide) - There are three atoms of oxygen for every one atom of sulphur
When numbers are written as 'subscripts' in compounds (i.e. they are written below and to the right of the element symbol), this tells us how many atoms of that element there are in relation to other elements in the compound. For example in nitrogen dioxide (NO
2 ) there are two oxygen atoms for every one atom of nitrogen. In sulphur trioxide (SO
3 ), there are three oxygen atoms for every one atom of sulphur in the compound. Later, when we start looking at chemical equations, you will notice that sometimes there are numbers
before the compound name. For example, 2H
2 O means that there are two molecules of water, and that in each molecule there are two hydrogen atoms for every one oxygen atom.
Naming compounds
The formula for calcium carbonate is CaCO
3 .
Is calcium carbonate a mixture or a compound? Give a reason for your answer.
What is the ratio of Ca:C:O atoms in the formula?
Give the name of each of the following substances.
KBr
HCl
KMnO
4
NO
2
NH
4 OH
Na
2 SO
4
Give the chemical formula for each of the following compounds.
potassium nitrate
sodium iodide
barium sulphate
nitrogen dioxide
sodium monosulphate
Refer to the diagram below, showing sodium chloride and water, and then answer the questions that follow.
What is the chemical formula for water?
What is the chemical formula for sodium chloride?
Label the water and sodium chloride in the diagram.
Give a description of the picture. Focus on whether there are elements or compounds and if it is a mixture or not.
What is the formula of this molecule?
C
6 H
2 O
C
2 H
6 O
2C6HO
2 CH
6 O
Questions & Answers
Discuss the differences between taste and flavor, including how other sensory inputs contribute to our perception of flavor.
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include:
1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Anatomy is the study of the structure of the body, while physiology is the study of the function of the body. Anatomy looks at the body's organs and systems, while physiology looks at how those organs and systems work together to keep the body functioning.
Enzymes are proteins that help speed up chemical reactions in our bodies. Enzymes are essential for digestion, liver function and much more. Too much or too little of a certain enzyme can cause health problems
Kamara
yes
Prince
how does the stomach protect itself from the damaging effects of HCl
the normal temperature is 37°c or 98.6 °Fahrenheit is important for maintaining the homeostasis in the body
the body regular this temperature through the process called thermoregulation which involves brain skin muscle and other organ working together to maintain stable internal temperature
