Question

Match the atoms which might substitute for one another. Match the items in the left column to the items in the right column.

Answer 1

Atoms which might substitute for one another can be found in the same column in the periodic table. 
So, since Si and C are found in the same column, they can substitute each other.
1. Si = C
2. K = Na
3. Nb = V
4. Cu = Ag
5. P = As
6. Mg = Ca

Answer 2

Answer:

Si = C

K = Na

Nb = V

Cu = Ag

P = As

Mg = Ca