Provided the right cpu for the socket is being used, yes there's a fair amount of resistance. Make sure the arrow on the cpu is aligned with the arrow on the socket and that the guide pins fit the notches in the cpu. Rest the cpu in the socket with the lid open, make sure the plastic protector is out of the way. In other words don't try to leave the plastic socket lid on and install the cpu, it's just there to cover the socket to preserve the delicate pins.
With more recent i5's they've relied on lga or land grid array meaning the cpu itself has flat metal contacts (lands). The pins in the socket on the motherboard are angled so that when the cpu is locked into place it presses down and bows all those pins. That ensures tension and...