Can Arduino run at 5V on 8MHz Bootloader ?
Explanation:
I want to minimize the circuit and i want to drive relay on arduino without any transistor or driver.
so please tell me will it work if i give it 5V or will i burn it?
Thank you.
If you don´t use transistor, you will burn your ATMEGA.
Thank you for your answer 
i was thinking the same.
The ATMEGA pin can source (sorry, I don´t know if rigth is "source" or "supply") MAX 20mA
common coil of relay need 180mA at 5V.
Got it, thank you.
"Can Arduino run at 5V on 8MHz Bootloader ?"
Yes it can.
Doesn't help if relay drive >35mA is needed as noted earlier.
The clock rate restriction is that lower voltages mean a lower maximum clock - so 3V3 is only guaranteed upto
about 12MHz for instance, and 5V to 20MHz... Running a lower clock rate has no adverse effects (except running
slower!)