Topic 2- Periodicity

Question 1

What is the atomic radius?

Answer 1

Half the distance between the nuclei of two bonded atoms of the element.

Question 2

What does the size of an atom/ion depend on?

Answer 2

The nuclear charge (same as the atomic no)

The no of energy shells

Question 3

What the pattern in atomic size going across a period?

Answer 3

The covalent atomic radius decreases(atoms get smaller) because the nuclear charge increases, attracting the outer electrons more strongly pulling them in closer without any additional shielding

Question 4

What the pattern in atomic size going down a group?

Answer 4

The covalent radius increases (atoms get larger) because of the addition of extra electrons shells

Question 5

Why is size a positive ion smaller than the size of the atom?

Answer 5

It has less electron shells

Question 6

What is trend for size of positive ions going across the period?

Answer 6

The size of + ions decreases because the increased nuclear charge attracts the electrons in the full outer shell more strongly

Question 7

Why is the size of a negative ion slightly larger than the size of the atom?

Answer 7

Because it will have the same nuclear charge attracting a larger number of out shell electrons

Question 8

What is the first ionisation energy?

Answer 8

Is the energy required to remove one mole of electrons from one Mole of atoms in the gaseous state

Question 9

What is the second ionisation energy?

Answer 9

Is the energy required to remove one mole of electrons from one mole of 1+ ions in the gaseous state

Question 10

What is the third ionisation energy?

Answer 10

Is the energy required to remove one mole of electrons from one mole 2+ ions in the gaseous state

Question 11

What is the trend for value of the 1 I.E. going across a period?

Answer 11

An overall increase as the nuclear charge increases, attracting the outer electrons more strongly. More energy is needed to remove the outer electron

Question 12

What is the trend for value of the 1st I.E. going down a group? (2)

Answer 12

It decreases as the outer electron is being removed from an energy level that is further away from the nucleus so the electron is attracted less strongly by the nucleus and less energy is needed to remove it.
The outer electrons are more shielded from the nucleus by an increasing number of inner electrons

Question 13

What is electronegativity?

Answer 13

A measure of the attraction of an atom for the electrons in a bond

Question 14

What is the trend in electronegativity across a period?

Answer 14

Increases as the nuclear charge increases so the attraction of the nucleus for bonding electrons increases

Question 15

What is the trend in electronegativity going down a group?

Answer 15

Decreases because the atoms have more electron shells (bigger radius) so the binding electrons are further away and more shielded from the nuclear charge

Question 16

Why do noble gases have extremely high I.Es?

Answer 16

They have a full outer electron shell so they are stable and extremely resistant to the removal of an electron

Question 17

Why is there no electronegativity for a Noble gas?

Answer 17

Do not form bonds

Question 18

How are the elements arranged in today’s periodic table?

Answer 18

Elements are arranged in order of increasing atomic number

Question 19

What is periodicity?

Answer 19

is the regular recurrence of similar properties when elements are arranged in order of increasing atomic number.

Question 20

What is shielding?

Answer 20

is where the electron shells between the outer shell and the nucleus ‘shield’ the outer electron from the nuclear charge

Question 21

Why is the covalent atomic radius a periodic property?

Answer 21

As there is a decrease in the covalent atomic radius across each period

Question 22

Why is there no value for the atomic radius of helium, argon and neon?

Answer 22

They do not form bonds

Question 23

Why s the 1st ionisation energy a periodic property?

Answer 23

As you go across each period the 1st ionisation energy increases.

Question 24

In any given period, what element will have the highest and lowest 1st ionisation energy?

Answer 24

Highest- The noble gas

Lowest- The alkali metal

Question 25

What is the main factor in the trend for the 1st ionisation energy going across a period?

Answer 25

The nuclear charge

Question 26

What is the main factor(s) in the trend for the 1st ionisation energy going down a period?

Answer 26

Distance and shielding

Question 27

Why does the ionisation energy increase as more electrons are removed from an element?

Answer 27

Because of the larger attraction of the nucleus of the remaining electrons

Question 28

What has the highest 2nd ionisation energy in the period? Why?

Answer 28

The alkali metal as the 2nd electron in the alkali metal is being removed from a stable full outer shell that is closer to the nucleus and so is less shielded, more energy is needed to remove it.

Question 29

Why is the 1st ionisation energy of the alkali metal much less than that of the halogen in the same period?

Answer 29

As it has a lower nuclear charge so it attracts the outer electron less strongly so less energy is needed to remove it

Question 30

Why is fluorine the most electronegative element?

Answer 30

Because it is a small atom with a high nuclear charge for its size so it attracts the electrons in a bond strongly