Is there a reason why the crystal oscillator on the Leonardo is different from the crystal on the Uno? Could you put the crystal on the uno on the Leonardo?
Is there a reason why the crystal oscillator on the Leonardo is different from the crystal on the Uno?
Yes.
The Uno uses a separate Atmega16U2 for the serial communications and that uC has a crystal for the timebase to ensure accurate serial communications at high BAUD rates. The Atmega328P-PU uC is not doing critical communications, therefore a less expensive ceramic resonator is used.
The Leonardo uses a single 32U4 for the entire board, communications and computing. A crystal is more appropriate in this case.
There are some clones out in the Leonardo world that may use resonators. The Arduino official description is:
The Arduino Leonardo is a microcontroller board based on the ATmega32u4 (datasheet). It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button.
One would be ill-advised to put a resonator on the Leonardo.
Ray