An atom with atomic diagram has chemical properties most similar to calcium

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?

Which is a substance that can be separated by physical means and is not the same throughout

When a pendulum is held high and taut and then is released, the pendulum begins to swing. what’s the correct order of the energy transformations in this example? (pe stands for potential energy.)