1 1 Elements

I. Elements

Page 1

Topic

I.

Elements

Reading Assignment

Integrated Chemistry Today (2nd Ed.), L.H.M Chung, Book 1A, pg 10 – 15

Objectives

1.1 – be aware that matter is made of elements in a variety of states and forms – recognise that elements can in general be classified into metals and non-metals, some elements can be further classified as semi-metals and noble gases – write names and symbols for elements – plan and describe experiments to show that metals are conductors while non-metals are non-conductors of electricity

Notes

I.

Elements

Although chemistry is a study of properties of substances, there are millions and billions of different substances in the world, it is almost impossible to study them all. However, scientists have found that all substances are made up of limited number of different components, called elements. e.g. water is a substance comprised of elements hydrogen and oxygen. Only 92 elements are naturally occurring. Until Nov 1994, other 19 elements were made by the scientists in the laboratory and made up to a total of 111 elements.

A. Names and symbols of elements In order to save time, elements are usually represented by using symbols. e.g. H for hydrogen, Na for sodium. The first letter of a symbol must be a capital letter and the following letter must be a small letter, special attention have to be paid on this. Example :

Co is the symbol for element cobalt. but CO is the formula for compound carbon monoxide.

Rules of assigning symbols for elements the first letter of the name is used. Carbon C because C is used for carbon, the first and the second letters are used. Calcium Ca the first and the second letters are used. Cobalt Co because Co is used for cobalt, Cu from the Latin word Cuprum, which Copper Cu means copper, is used. Even the first and the second letters cannot tell the difference between Chlorine Cl chlorine and chromium, the first and the third letter are used. Chromium Cr

I. Elements

Page 2

Name of element

Symbol

Name of element

Symbol

Name of element

Symbol

1.

hydrogen

_______

13. aluminium

_______

28. nickel

_______

2.

helium

_______

14. silicon

_______

29. copper

_______

3.

lithium

_______

15. phosphorus

_______

30. zinc

_______

4.

beryllium

_______

16. sulphur

_______

35. bromine

_______

5.

boron

_______

17. chlorine

_______

47. silver

_______

6.

carbon

_______

18. argon

_______

50. tin

_______

7.

nitrogen

_______

19. potassium

_______

53. iodine

_______

8.

oxygen

_______

20. calcium

_______

56. barium

_______

9.

fluorine

_______

24. chromium

_______

78. platinum

_______

10. neon

_______

25. manganese

_______

79. gold

_______

11. sodium

_______

26. iron

_______

80. mercury

_______

12. magnesium

_______

27. cobalt

_______

82. lead

_______

B. Classification of elements Elements can be classified by different ways. For example, elements can be classified according to the physical states or metallic properties. 1.

Physical states of elements

Among the 111 elements, only 2 are liquid (bromine and mercury), 11 are gas and all of the rest are solid.

2.

Metal, non-metal and semi-metal and noble gas

Or in another way, according to the metallic properties, most of the elements are metal, with some non-metal and a few metalloid (semi-metal). Metalloid (semi-metal) is a very small group of element with electrical conductivity much lower than metal but much higher than non-metal. They are usually used in manufacturing of semi-conductor (integrated circuit). The followings are some examples of elements : (a) Metals:

aluminium, barium, beryllium, calcium, chromium, cobalt. copper, gold, iron, lead, lithium, magnesium, manganese, mercury nickel, platinum, potassium, silver, sodium, tin and zinc (b) Non-metals: bromine, carbon, chlorine, fluorine, hydrogen, iodine, nitrogen, oxygen, phosphorus and sulphur (c) Semi-metals: boron and silicon (d) Noble gases: argon, helium and neon Noble gases are also non-metals, but due to the low reactivity, a special name is given to this group of elements. N.B.

Strictly speaking, the classification of metal, metalloid and non-metal is for element only. For example, water cannot be classified as a non-metal because it is not an element.

I. Elements

Page 3 Name of element

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

hydrogen helium lithium beryllium boron carbon nitrogen oxygen fluorine neon sodium magnesium aluminium silicon phosphorus sulphur chlorine argon

Symbol

Physical State

Metal / Metalloid / Non-metal

H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar

Gas Gas Solid Solid Solid Solid Gas Gas Gas Gas Solid Solid Solid Solid Solid Solid Gas Gas

Non-metal Non-metal Metal Metal Metalloid Non-metal Non-metal Non-metal Non-metal Non-metal Metal Metal Metal Metalloid Non-metal Non-metal Non-metal Non-metal

Name of element

19. 20. 24. 25. 26. 27. 28. 29. 30. 35. 47. 50. 53. 56. 78. 79. 80. 82.

potassium calcium chromium manganese iron cobalt nickel copper zinc bromine silver tin iodine barium platinum gold mercury lead

Symbol

Physical State

Metal / Metalloid / Non-metal

K Ca Cr Mn Fe Co Ni Cu Zn Br Ag Sn I Ba Pt Au Hg Pb

Solid Solid Solid Solid Solid Solid Solid Solid Solid Liquid Solid Solid Solid Solid Solid Solid Liquid Solid

Metal Metal Metal Metal Metal Metal Metal Metal Metal Non-metal Metal Metal Non-metal Metal Metal Metal Metal Metal

a) Properties of metal

Appearance Colour

Strength Conductivity of electricity and heat

Metals shiny, have lustre usually silvery white, except gold and copper which are reddish brown malleable, ductile, hard and strong (except mercury) high

Non-metals dull if solid (except graphite) various coloured e.g. carbon is black, sulphur is yellow, bromine is reddish brown and hydrogen is colourless brittle if solid low (except graphite)

Graphite is a kind of carbon. It is very special, in certain aspect, it is very similar to metal.

b) Testing conductivity of elements Except graphite, only metal conducts electricity well. Therefore, it would be very convenient to classify an element into metal or non-metal by testing the conductivity of the element.

I. Elements

Glossary

Page 4 element malleability

metal non-metal ductility brittle

metalloid (semi-metal) graphite symbol

noble gas

dull

Past Paper Questions 95 26 B

99 45 B

26 Which of the following elements is a semi-metal ? A. Hg B. Si C. C D. Be

45 Sulphur is classified as a non-metal.

Sulphur does not react with dilute acids.

shiny