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) $1,1\cdot 10^{6}$. The speed of an electron in the 3rd orbit of a hydrogen atom can be calculated using the formula $v = \frac{Z^2 \cdot 9 \cdot 10^9}{2 \}$, where $Z$ is the atomic number, $n$ is the principal quantum number, and $h$ is Planck's constant. For hydrogen, $Z = 1$ and $n = 3$, so the speed is approximately $1,1\cdot 10^{6} \, m/s$.