The uncertainty in the position of an electron orbiting an atom is 0.3 Å. What is the uncertainty in its speed?

According to Heisenberg's Uncertainty Principle, we cannot simultaneously determine the position and momentum of a particle precisely and that there is always some uncertainty in this. Mathematically, the principle is given as:

where,  is the uncertainty in the position and  is the uncertainty in momentum of the object, while h is the Planck's constant.

Here, the uncertainty in the position of electron is 0.3 x 10^-10 m. The mass of an electron is 9.12 x 10^-31 kg and the value of Planck's constant is 6.626 x 10^-34 Js. 

Thus, the uncertainty in velocity of the electron is

Thus, there is a minimum uncertainty of 1.93 x 10^6 m/s in the velocity of the electron. 

Hope this helps.