The family of metals having valency two

The family of metals having valency one .

The family of non-metals having valency one .

Two elements having valency 4.

Find the differential equation of the family of circles having their centres on the line y=10 and touching the X axis.

Write the names from the description. Two elements having valency 4.

Name the following : Two metals having low melting points.

Answer the following question in one sentence : Name two metals having low melting points and boiling points.

The pair of compounds having metals in their highest oxidation state is "________________" .

Form the differential equation of family of lines having intercepts a and b on the co-ordinate axes respectively.