C1.5 PRINCIPLES OF CHEMISTRY

Question 1

In which group of periodic Table is magnesium?

Answer 1

group II

Question 2

Why are noble gases ( Group VIII or 0 ) unreactive?

Answer 2

The noble gases have full outer electron shells or have eight electrons in their outer electron shells and so do not easily lose or gain electrons.

Question 3

How do you know that phosphorus oxide is not an ionic compound?

Answer 3

Both phosphorus and oxygen are non-metals. (A metal is needed to form an ionic bond)

Question 4

Why does an ionic compound such as magnesium oxide not conduct electricity when it is solid?

Answer 4

The ions are held together strongly in a giant lattice structure. The ions can vibrate but cannot move around.

Question 5

Suggests a reason why magnesium oxide has a higher letting point than sodium chloride.

Answer 5

. +
Sodium chloride is made up of singly charged ions, Na and
-
Cl ,
whereas the magnesium ion in magnesium oxide has a
2+
double charge, Mg .

The higher the charge on the positive ion, the stronger the attractive forces between the positive ion and the negative ion.

Question 6

Why does a covalently bonded compound such as carbon dioxide have a relatively low melting point?

Answer 6

The INTERMOLECULAR forces of attraction between the molecules are week.

Question 7

Would you expect a covalently bonded compound such as ethanol to conduct electricity? Explain your answer.

Answer 7

No. There are no ions or delocalized electrons present.