In elements of group 14,:Which is used as semi-conductor?

In elements of group 14,:Which forms the most acidic oxide?

In elements of group 14,:Which is normally found in +2 oidation state?

Name a member of group 14 element in the periodic table which is used as semi conductor.

The hydride of V group element which is used in the manufacture of artificial silk

Based on the group valency of elements state the formula for the following giving justification for each : (i) Oxides of 1^(st) group elements, (ii) Halides of the elements of group 13, and (iii) Compounds formed when an element of group 2 combines with, an element of group 16.