Periodicity

Question 1

How does the periodic table arrange the known elements?

Answer 1

In order of increasing proton number

Question 2

Does the number of shells in elements along a period vary?

Answer 2

No - all the elements along a period have the same number of shells

Question 3

Does the number of outer electrons of each element in a group vary?

Answer 3

No - all elements down a group have the same number of outer electrons

Question 4

Elements in the same group have similar…

Answer 4

Chemical properties

Question 5

What do elements in the same block have the same of?

Answer 5

The have their outer electrons occupying the same orbital

Question 6

What is periodicity?

Answer 6

The study of repeating trends in the properties of elements across each period of the periodic table

Question 7

Is Calcium an anomaly for its electron configuration/ why?

Answer 7

Yes - it’s 4s shell is filled and it’s 3d shell is not

Question 8

Is chromium an anomaly/ why?

Answer 8

Yes - it’s 3d and 4s subshells fill singularly and there are no paired electrons in either sub shell

Question 9

How does atomic radius vary along a period?

Answer 9

It decreases

Question 10

Why does atomic radius vary along a period?

Answer 10

Decrease since there is an increased nuclear charge for the same number of electron shells, so the outer electrons are pulled in closer to the nucleus as the increased charge produces a greater attraction

Question 11

How does atomic radius vary down a group?

Answer 11

It increases

Question 12

Why does atomic radius vary down a group?

Answer 12

With each element, a shell is added which increases the distance between the outer electrons and nucleus, reducing the power of attraction. More shells increased shielding so nuclear attraction is reduced.

Question 13

What is shielding?

Answer 13

The repulsion between electrons in different inner shells

Question 14

What is shielding’s effect on the net attractive force between the positive nucleus on the outer shell electrons?

Answer 14

It reduces it

Question 15

What is the first ionisation energy?
(kJ/mol)

Answer 15

The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state

Question 16

Show sodium’s first ionisation energy in an equation:

Answer 16

Na (g) —> Na+ (g) + e-

Question 17

When do successive ionisation energies occur?

Answer 17

When further electrons are removed.

Question 18

Why do successive ionisation energies require more energy?

Answer 18

As the electrons are removed, the electrostatic force of attraction between the positive nucleus and negative outer electrons increases, so more energy is needed to overcome the attraction

Question 19

Why does first ionisation energy across a period overrall increase?

Answer 19

There is decreasing atomic radius and greater electrostatic forces of attraction across a period

Question 20

Why does the first ionisation energy decrease down a group?

Answer 20

There is an increasing atomic radius and an increase in electron shielding which reduces the effect of the electrostatic forces of attraction across a period

Question 21

What is a successive ionisation energy?

Answer 21

The process of removing one mole of electrons from one mole of gaseous ions.

Question 22

What does a large jump in successive ionisation energies indicate?
(E.G large jump between 3rd and 4th)

Answer 22

Which group an element is in (indicated there are 3 outer electrons so in group 3)

Question 23

What are two exceptions from the trend of ionisation energies increasing across period 2?

Answer 23

• boron
• oxygen

Question 24

Why is boron an exception?

Answer 24

Has a lower 1st ionisation energy than expected by the general trend as there is an energy difference between the 2s and 2p subshells - removed from a higher energy level that is further from the nucleus so is held less strongly.

Question 25

Why is oxygen an exception?

Answer 25

Has a lower 1st ionisation energy than expected due to repulsion within the 2p orbital as there are 2 Electrons in it - repulsion is destabilising in comparison to nitrogen and allows Oxygen’s electron to be more easily removed.

Question 26

What are the two exceptions for increasing ionisation energies across period 2?

Answer 26

-aluminium
- sulfur

Question 27

Why is aluminium’s 1st ionisation energy lower than expected by the general trend?

Answer 27

There is an energy difference between the 3s and 3p sub shell - electron is being removed from a higher energy level that is further from the nucleus so is held less strongly

Question 28

Why is sulfur’s 1st ionisation energy lower than otherwise expected?

Answer 28

Repulsion within the 3p orbital as there are 2 electrons in the same one - repulsion is destabilising in comparison to the configuration of phosphorus and allows the electron to be removed more easily.