In other words, inner electrons surrounding our nucleus shield the outermost electron from some of that charge due to our protons decreasing the net pull of the nucleus on our outermost electron. Now, the final amount of charge felt by this outermost electron due to our proton nucleus is called the effective nuclear charge. In other words, because there is a second electron found even closer to our nucleus, that means the charge that this guy will feel due to this proton nucleus will be less than what it would feel if this electron wasn't here. That means if we use the same exact formula for Coulomb's law for this guy, we'll get this result. In other words, the force that this guy feels this charge due to our proton nucleus. This guy divided by R squared times K will be greater than the actual force that this guy feels.