A sound banking system has several essential elements according to the document. It must maintain liquidity by keeping some assets easily convertible to cash to meet depositor demands. It must ensure safety by making secure loans and investments to avoid risks to depositor funds. It needs stability by rationally expanding and contracting credit according to economic conditions without booms and inflation. It requires elasticity to adjust lending while following central bank directives. And it must earn profits through prudent policies to remain viable and pay expenses.