Trends in the properties of elements of period 3 Flashcards
Which elements in period 3 are metals?
Na, Mg and Al
Which element in period 3 is a semi-metal?
Si
Which elements in period 3 are non-metals?
P, S, Cl
Wich element in period 3 is a noble gas?
Ar
Which block is sodium and magnesium in?
S-block
Which block is Al, Si, P, S, Cl and Ar in?
P-block
What kind of structure does Na, Mg and Al form?
Giant metallic
What kind of structure does Si form?
Macromolecular
What kind of structure does P, S Cl form?
molecular
What kind of structure does Ar form?
Atomic
How many atoms of phosphorus makes a phosphorus molecule?
P4
How many atoms of sulfur makes a sulfur molecule?
S8
How many atoms of chlorine makes a chlorine molecule?
Cl2
How many atoms of argon makes a argon molecule?
Ar (1)
Describe the melting point of the period 3 elements
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?
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.
Why does the melting and boiling points of the metals increase as you go from sodium to aluminium?
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.
Why does the melting points of the non-metals decrease from sulfur to phosphorus to chlorine?
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.
