Periodicity

Question 1

What is Periodicity?

Answer 1

Periodicity is the repeating pattern of physical or
chemical properties going across the periods.

Question 2

Electron configuration of Na

Answer 2

1s2 2s2 2p6 3s1

Question 3

Electron configuration of Mg

Answer 3

1s2 2s2 2p6 3s2

Question 4

Electron configuration of Al

Answer 4

1s2 2s2 2p6 3s2 3p1

Question 5

Electron configuration of Si

Answer 5

1s2 2s2 2p6 3s2 3p2

Question 6

Electron configuration of P

Answer 6

1s2 2s2 2p6 3s2 3p3

Question 7

Electron configuration of S

Answer 7

1s2 2s2 2p6 3s2 3p4

Question 8

Electron configuration of Cl

Answer 8

1s2 2s2 2p6 3s2 3p5

Question 9

Electron configuration of Ar

Answer 9

1s2 2s2 2p6 3s2 3p6

Question 10

Describe how atomic radius affects the trend of period 3 elements.

Answer 10

Atomic radii decrease from left to right across a
period, because the increased number of protons
create more positive charge attraction for electrons
which are in the same shell with similar shielding.

Question 11

Describe how the 1st ionisation energy generally affects the trend of period 3 elements.

Answer 11

There is a general trend across to increase. This is due to the increasing number of protons as the electrons are being added to the same shell.

Question 12

What is the exception for Mg-Al?

Answer 12

There is a small drop between Mg + Al.
Mg has its outer electrons in the 3s sub-shell, whereas
Al is starting to fill the 3p subshell.
Al’s electron is slightly easier to remove
because the 3p electrons are higher in energy.

Question 13

What is the exception for P-S?

Answer 13

There is a small drop between phosphorous and sulfur.
Sulfur’s outer electron is paired up with another electron in the same 3p orbital. When the second electron is added to an orbital there is a
slight repulsion between the two negatively charged electrons which make the second electron easier to remove.

Question 14

Describe the melting and boiling point in Na, Mg, and Al.

Answer 14

For Na, Mg, and Al- Metallic bonding: strong bonding – gets stronger the more electrons there are in the outer shell that is released to the sea of electrons.
A smaller-sized ion with a greater positive charge also makes the bonding stronger.
Higher energy is needed to break bonds.

Question 15

Describe the melting and boiling point in Si.

Answer 15

Si is Macromolecular: many strong covalent bonds between
atoms, high energy needed to break covalent bonds– very high mp +bp

Question 16

Describe the melting and boiling point in P, S, and Cl.

Answer 16

Cl2 (g), S8 (s), P4 (S)- simple molecular : weak van der Waals between molecules, so little energy is needed to break them – low mp+ bp

S8 has a higher mp than P4 because it has more electrons
(S8 =128)(P4=60) so has stronger v der w between molecules

Question 17

Describe the melting and boiling point in Ar.

Answer 17

Ar is monoatomic so weak van der Waals between atoms.