The periodic table

Question 1

How are elements in the periodic table arranged?

Answer 1

They are arranged in order of increasing proton numbers.

Question 2

What do the periods in the periodic table represent?

Answer 2

The period number corresponds to the number of electron shells an element has.

Question 3

Why do elements in the same group have similar chemical properties?

Answer 3

They have the same number of valence electrons. Hence, have similar chemical properties

Question 4

What do the groups in the periodic table represent?

Answer 4

Apart from the transition elements, the ‘ones’ place in the group number corresponds to the number of valence electrons.

Question 5

Why does the metallic character of elements decrease across the period (left to right)?

Answer 5

Elements are less likely to lose its valence electron(s).

Question 6

Why does the atomic radius increase down the group?

Answer 6

The number of electron shells increase down the group.

Question 7

Why are group 1 metals called alkali metals?

Answer 7

They react with water to form an alkali solution

Question 7

What are the chemical properties of alkali metals?

Answer 7

• very reactive, usually stored in oil
• reacts with H2O to form alkali solution and H2 gas
• powerful reducing agents (give electrons to other substances)
• form white-coloured compounds that dissolve in water to give a colourless solution

Question 8

What are the physical properties of alkali metals?

Answer 8

• soft, can be cut easily
• low m.p. and b.p.
• low density
• good conductor of electricity and heat (due to mobile electrons)

Question 9

What are the trends down group 1?

Answer 9

• density generally increases
• reactivity increases
• m.p. and b.p. decreases

Question 10

Why does reactivity increase down group 1?

Answer 10

The no. of valence shells increases. The valence electron is further away from the nucleus and the attraction force between the valence electron and the protons in the nucleus decreases. Hence, valence electrons are more easily lost.

Question 11

What are the chemical properties of halogens?

Answer 11

• can undergo displacement reactions. A more reactive halogen can displace a less reactive halogen from its salt solution
• powerful oxidising agents (gain electrons from other substances)

Question 11

What are group 17 elements?

Answer 11

They are non-metals and are called halogens

Question 11

What are the physical properties of halogens?

Answer 11

• exist as diatomic molecules
• low m.p. and b.p.
• coloured substances

Question 11

What are the trends down group 17?

Answer 11

• reactivity decreases
• m.p. and b.p. increases
• colour intensity increases (becomes darker)

Question 12

Why does reactivity in group 17 decrease?

Answer 12

No. of electron shells increase. As distance between valence shell and nucleus increases, the attraction force decreases. Hence, more difficult to gain one valence electron.

Question 13

What are noble gases?

Answer 13

• group 18 elements;
• have full valence shells, are unreactive;
• do not gain/lose or share electrons and rarely react to form compounds

Question 14

What are the physical properties of noble gases?

Answer 14

• exist as individual atoms (monatomic)
• low m.p. and b.p.
• colourless gases