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
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
