Under the correct conditions, the element molybdenum emits X-rays with a characteristic wavelength of 0.711A (7.11*10^-11m). These X-rays are used in diffraction experiments to determine molecular structures. How fast does an electron need to be moving to have the same wavelength as these X-rays?

Wavelength=h/mv

7.11*10^-11m= (6.626*10^-34J*s) / mv

I'm stuck. How do I know what "m" is? Is it just the atomic mass of Molybdenum, 95.9amu?

No. Aren't you interested in the speed of the electron. So it's the mass of the electron (in kg I think).

Oh, yes that's right. Mass of electron= 9.11*10^-31kg.

Therefore v=1.02*10^7m/s

That looks ok to me. I didn't check the arithmetic.

To determine the value of "m" in the equation, you need to consider the particle nature of electrons. Electrons can be described as both particles and waves, and in this case, we are treating them as particles with a certain mass.

The mass of an electron is approximately 9.10938356 × 10^-31 kilograms. It is essential to use the SI unit for mass (kg) in order to maintain consistency with the other units in the equation.

Given this information, you can substitute the value of "m" into the equation and solve for "v," which represents the velocity:

7.11 × 10^-11 m = (6.626 × 10^-34 J·s) / (9.10938356 × 10^-31 kg) * v

Now, you can rearrange the equation to solve for "v":

v = (6.626 × 10^-34 J·s) / (9.10938356 × 10^-31 kg) * (7.11 × 10^-11 m)

Calculating this expression will give you the value of velocity "v."