1. The speed of electron in the 3rd orbit of hydrogen atom is (m/s) 1) 2,2cdot 10^-6 0,5cdot 10^5 2) 1,1cdot 10^6 3) 7,3cdot 10^5 4) 6,6cdot 10^6 5)

The correct answer is 2) . The speed of an electron in the 3rd orbit of a hydrogen atom can be calculated using the formula , where is the atomic number, is the principal quantum number, and is Planck's constant. For hydrogen, and , so the speed is approximately .