PciE x1 wireless adapter on 2nd pciE x16 slot, without any graphics card in pcie x16 slot 1

[AlooZ]

I have a dell optiplex 7020 MT. Motherboard is this 

Genuine-Dell-Optiplex-7020-Motherboard-DP-N-F5C5X-LGA-1150.

See this pic: https://drive.google.com/open?id=0B1ZxG1j27AlgMGNFZ01OS...

In the pic, can I install my pciE x1 wireless adapter in the number 1 labeled black slot? And install a gtx 750 ti graphcis card on the number 5 labeled slot? I can't install the pcie x1 card on the 3 labeled because the gtx 750 ti requires two brackets, and it would take the place on the pcie x1 slot.

I dont have the gtx 750 ti yet. I will still buy it. Before buying it, i tried installing the pcie x1 wireless adapter on the number 1 labeled slot. But computer would turn on, but my mouse, keyboard, monitor wouldn't. Is it becuase the number 5 slot is empty right now? So when I get my graphis card and install it in the number 5, and my wireless card in the number 1, will everything work fine?

I'm sorry if i confused you a lot. Please help me.

 

And btw i installed a 520w power supply. Will the gtx 750 ti work?

[themctipers]

yes you can.

[djboy6480]

yes PCIe is backwards compatible. Basicly if it fits it works
just do GPU in 5 and Wifi in 1

[AlooZ]

Ok i don't have the gpu yet. I tried putting the wifi in 1, but my pc doesn't work when i do that.