It says 1155 in the technical details. 1156 and 1155 are two completely different sockets, they are not interchangeable, and you cannot use an 1156 CPU in an 1155 socket or vice versa. It isn't like the AMD sockets where some newer CPUs will work on an older socket, provided you have the appropriate BIOS. I know, it's really stupid, and intel only changed the socket for Sandy Bridge in order to sell more motherboards, but that's the way it is. The i3 2100 probably will cost about the same as an i3 5xx, while delivering better performance, so just get the 2100 if you are looking for a CPU in that price bracket for that particular motherboard.
If you really want the i3 5xx CPU, get an 1156 board, though that's not advisable as 1156 is a dead socket, and there is no upgrade path beyond the Clarkdale and Lynnfield CPUs.