2.1 - Periodicity

Question 1

How are elements in the periodic table arranged?

Answer 1

According to their proton number.

Question 2

What is a period on the periodic table?

Answer 2

The horizontal rows.

Question 3

What is a group on the periodic table?

Answer 3

The vertical columns.

Question 4

What does the group number indicate on the periodic table?

Answer 4

The number of outer electrons of an element.

Question 5

What are the 4 blocks of the periodic table?

Answer 5

• S-Block
• P-Block
• D-Block
• F-Block

Question 6

What elements are in each block of the periodic table?

Answer 6

• S-Block = groups 1 and 2
• P-Block = groups 3 to 0
• D-Block = transition metals
• F-Block = radioactiove metals.

Question 7

What is periodicity?

Answer 7

The study of trends within the periodic table. Often these trends are linked to elements electronic configurations.

Question 8

What is the trend in atomic radius along a period?

Answer 8

Along a period, atomic radius decreases.

Question 9

Why does the atomic radius decrease along a period?

Answer 9

• Atomic radius decreases due to an increased nuclear charge for the same number od electron shells.
• This means that the outer electrons are pulled in closer to the nucleus because the charge produces a greater attraction.
• As a result, the atomic radius is reduced.

Question 10

What is the trend in atomic radius down a group?

Answer 10

Atomic radius increases.

Question 11

Why does atomic radius increase down a group?

Answer 11

• With each increment down a group, an electron shell is added.
• This increases the distance between the outer electrons and the nucleus, reducing the power of attraction.
• More shells also increases electron shielding, whereby the inner shells create a ‘barrier’ that blocks the attractive forces.
• The nuclear attraction is reduced further and atomic radius increases.

Question 12

What is the trend in IE along a period?

Answer 12

IE increases along a period.

Question 13

Why does IE increase along a period?

Answer 13

It increases because atomic radius decreases, hence nuclear charge increases. This means thatthe outer electrons are held more strongly so more energy is required to remove the outer electron and ionise the atom.

Question 14

What is the trend in IE going down a group?

Answer 14

IE decreases down a group.

Question 15

Why does IE decrease going down a group?

Answer 15

The nuclear attraction between the nucleus and outer electrons reduces and shielding also increases. Both of these factors mean less energy is requires to remove the outer electron.

Question 16

What does the melting point of Period 3 elements depend on?

Answer 16

• The structure of the element.
• The bond strength.

Question 17

What happens to the MP across period 3 between sodium and aluminium?

Answer 17

• Sodium, magnesium and aluminium are all metals with metallic bonding. their melting points increase due to greater positive charge of their ions (Na = +1, Mg = +2, Al = +3)
• This means more elctrons are released in the form of free electrons.
• This increases the attractive electrostatic forces from Na to Al, therefore more enrgy is needed to break them.

Question 18

Why does the MP increase dramatically for Silicone in Period 3?

Answer 18

• Silicon has a very strong covalent structure.
• So more energy is required to break the strong covalent bonds - givingit a very high melting point.

Question 19

Why does the MP decrease in Period 3 between phosphorus and chlorine?

Answer 19

• Phosphorus, sulphur and chlorine are all simple covalent molecules held with weak van der waals forces.
• Less energy is needed to overcome these weak intermolecular forces, so these molecules have relatively low melting points.

Question 20

Why does argon have an even lower MP than chlorine?

Answer 20

• Argon is a noble gas that exists as individual atoms with a full outer shell of electrons.
• This makes the atom very stable and the van der waals forces between them are very weak.
• As a result, less energy is needed to overcome these weak forces and so argon exists as a gas at room temperature.