Why does sodium bond with chlorine and not lithium?

3 X ( g ) ⇄ Y ( g ) + Z ( s )

According to le chatelier principle increases in reactant concentration will shift equilibrium towrads right direction.

is constant with change in initial concentration of X.

Explanation:

                                      3 X ( g ) ⇄ Y ( g ) + Z ( s )

             Equilibrium constant for the reaction is as follows

                            =  

At equilibrium there is no change in the ratio of concentration of products to reactant if initial concentration change.

Therefore   is constant with change in initial concentration of X.