Periodic table

Question 1

Group

Answer 1

• vertical column containing elements having similar chemical properties
• group number represents number of outermost electrons present in atoms of elements

Question 2

Period

Answer 2

• horizontal row ; elements placed in increasing order of proton number
• as we move across a period, change from metals -> non-metals
• period represents number of shells in which electrons are placed in an atom

Question 3

Chemical properties of Group I ( Alkali metals )

Answer 3

1) all react with cold water with increasing vigour to form soluble hydroxides ( alkalis ) & H2 gas

2) burn in air, with increasing ease to form their oxides

3) all react with dilute acids with increasing ease to form salts & H2 gas

4) oxides known as basic oxides ; can dissolve in water to form alkalis

5) oxides & hydroxides can react with acids to form salts & H2O

6) hydroxides soluble in water ; called alkalis
7) chlorides are ionic compounds
8) reducing agents ; can be oxidised
9) carbonates are soluble in water but do not decompose on heating

Question 4

Physical properties of Group I metals

Answer 4

1) conductors of electricity in solid state ; contain metallic bonding
2) metals of low density ; increasing as we move down group
3) soft metals ; can be cut with knife
4) low MP & BP ; as we move down the group, MP & BP decrease

Question 5

Physical properties of Group VII ( Halogens )

Answer 5

1) non-conductors of electricity
2) low MP & BP, as we move down the group, MP& BP increase
3) increase in density as we move down the group
4) non-metals become more viscous but less volatile as we move down the group

Question 6

Chemical properties of Group VII elements

Answer 6

1) decrease in reactivity series as we move down the group
- fluorine most reactive

2) all non-metals with valency 1
- tendency to gain 1 electron to become an anion

3) form both ionic & covalent compounds
4) oxidising agents
5) their hydrides are acidic in aqueous state
6) their silver salts are insoluble in water

Question 7

Transition metals

Answer 7

found between Group II - Group III elements in period 4

Question 8

Properties of transition metals

Answer 8

• high MP & BP
• high densities
• high tensile strength
• good conductors of electricity
• form coloured compounds
• variable oxidation states
• can be used as catalysts

Question 9

Coloured compounds

Answer 9

• CUSO4 : Blue
• FeSO4 : Green
• K2CR2O7 : Yellow

Question 10

Group VIII -> Noble gases

Answer 10

• stable elements with stable electronic configuration
• valency 0
• neither gain nor lose electrons
• exist in monoatomic form
• unreactive elements ; inert / rare gases

Question 11

Uses of noble gases

Answer 11

1) He - weather balloons
2) Ne - advertising lights
3) Ar - electric bulbs
4) Kr - gas filled electric devices & lasers
5) Xe - electronic flash guns
6) Rn - natural radioactive gas