Periodicity

Question 1

What will all the elements within a period have the same number of?

Answer 1

Electron shells
(If you don’t worry about s and p sub-shells)
E.g. All period 2 gave 2 electron shells

Question 2

All elements within a group will have the same number of?

Answer 2

Electrons in their outer shell so have similar properties

Question 3

What does the group number tell you?

Answer 3

The number of electrons in the outer shell, group 4 elements have 4 electrons and so on. The exception is group 0 which have full electron shells that’s two electrons in helium, 8 electrons for all the others

Question 4

How can the periodic table be split?

Answer 4

Into an s block, d block, p block and f block.

Doing this shows which sub-shell all the electrons go into.

Question 5

What can you do you have labelled the blocks and numbered them?

Answer 5

Read off electronic structure of any element. Just start at the top and work your way across and down until you get the element

Question 6

What happens as the number of protons increases?

Answer 6

The positive charge of nucleus increases meaning electrons are pulled closer to the nucleus making the atomic radius smaller.

Question 7

What does the extra electrons gained across a period do?

Answer 7

Get added to the outer energy level so they don’t provide any extra shielding effect. Shielding is mainly provided by electrons in the inner shells

Question 8

How is the periodic table arranged?

Answer 8

Periods and groups by atomic (proton) number

Question 9

What will all the elements within a period have the same number of?

Answer 9

Electron shells
(If you don’t worry about s and p sub-shells)
E.g. All period 2 gave 2 electron shells

Question 10

All elements within a group will have the same number of?

Answer 10

Electrons in their outer shell so have similar properties

Question 11

What does the group number tell you?

Answer 11

The number of electrons in the outer shell, group 4 elements have 4 electrons and so on. The exception is group 0 which have full electron shells that’s two electrons in helium, 8 electrons for all the others

Question 12

How can the periodic table be split?

Answer 12

Into an s block, d block, p block and f block.

Doing this shows which sub-shell all the electrons go into.

Question 13

What can you do you have labelled the blocks and numbered them?

Answer 13

Read off electronic structure of any element. Just start at the top and work your way across and down until you get the element

Question 14

What happens as the number of protons increases?

Answer 14

The positive charge of nucleus increases meaning electrons are pulled closer to the nucleus making the atomic radius smaller.

Question 15

What does the extra electrons gained across a period do?

Answer 15

Get added to the outer energy level so they don’t provide any extra shielding effect. Shielding is mainly provided by electrons in the inner shells

Question 16

How is the periodic table arranged?

Answer 16

Periods and groups by atomic (proton) number

Question 17

What do melting points do across a period?

Answer 17

Vary because they depend on the structure and the bonding within them.

Question 18

What are sodium, magnesium and aluminium?

Answer 18

Period 3 metals

Question 19

What happens to sodium to aluminium melting point and boiling points?

Answer 19

Increase across the period because the metal- metal bonds get stronger. The bond get stronger because the metal ions have an increasing positive charge, an increasing number of delocalised electrons and decreasing radius

Question 20

Describe why silicon has a high melting point?

Answer 20

Macromolecular with a tetrahedral structure- string covalent bonds link all its atoms together. A lot of energy is needed to break these bonds so silicon has a high melting point

Question 21

Explain why phosphorus (P4), sulfur (S8) and chlorine (Cl2) have low melting point?

Answer 21

All molecular substances. Their melting points depend upon the strength of van der Waals forces which are weak and easily overcome

Question 22

What do more atoms in a molecule mean for van der Waal forces?

Answer 22

They are stronger van der Waals forces and sulfur is the bigger molecule so it’s got a higher melting point than phosphorus or chlorine

Question 23

Why does argon have a very low melting point?

Answer 23

It exists as individual atoms (monatomic resulting in very weak van der Waals forces.

Question 24

What do ionisation energies generally do across a period and why?

Answer 24

Increase because of the increasing attraction between outer shell electrons and the nucleus due to the number of protons increasing. (Few blips in this trend however)