Trends in the properties of elements of period 3

Question 1

Melting Point Trend Across Period 3

Answer 1

https://www.youtube.com/watch?v=9GudSTRCj_8

Question 2

Which elements in period 3 are metals?

Answer 2

Na, Mg and Al

Question 3

Which element in period 3 is a semi-metal?

Answer 3

Si

Question 4

Which elements in period 3 are non-metals?

Answer 4

P, S, Cl

Question 5

Wich element in period 3 is a noble gas?

Answer 5

Ar

Question 6

Which block is sodium and magnesium in?

Answer 6

S-block

Question 7

Which block is Al, Si, P, S, Cl and Ar in?

Answer 7

P-block

Question 8

What kind of structure does Na, Mg and Al form?

Answer 8

Giant metallic

Question 9

What kind of structure does Si form?

Answer 9

Macromolecular

Question 10

What kind of structure does P, S Cl form?

Answer 10

molecular

Question 11

What kind of structure does Ar form?

Answer 11

Atomic

Question 12

How many atoms of phosphorus makes a phosphorus molecule?

Answer 12

P₄

Question 13

How many atoms of sulfur makes a sulfur molecule?

Answer 13

S₈

Question 14

How many atoms of chlorine makes a chlorine molecule?

Answer 14

Cl₂

Question 15

How many atoms of argon makes a argon molecule?

Answer 15

Ar (1)

Question 16

Describe the melting point of the period 3 elements

Answer 16

Question 17

Look at the melting and boiling points of the elements in period 3. Why is it that silicon has the highest melting point and that the melting and boiling point decreases going from left to right on the graph?

Answer 17

Silicon forms a giant covalent molecule (a macromolecule) in which is kept together due to strong covalent bonds. These bonds require a large amount of energy to overcome and so silicon has the highest melting point. The elements on the left of the periodic table are metals and so form giant ionic structures as apposed tot he elements on the right which form small molecular or atomic structures. The larger structures require more energy to overcome the many bonds holding it together.

Question 18

Why does the melting and boiling points of the metals increase as you go from sodium to aluminium?

Answer 18

This is due to the strength of the metallic bonding. The charge of the ion increases and so more electrons join the delocalised electron sea.

Question 19

Why does the melting points of the non-metals decrease from sulfur to phosphorus to chlorine?

Answer 19

The melting points depend on the size of the van der Waals forces between the molecules. The van der Waals forces are determined by the number of eletrons in the molecule and how compact the molecule is. Sulfur forms S₈, phosphorus froms P₄ and chlorine forms Cl₂.