The quantum mechanical model states that

The quantum mechanical model of the atom users complex shapes or orbitals { Sometimes called Electron Clouds }, volumes of space in which there is likely to be an electron. So, this model is based on probability rather then certainty. Hope that helps

The quantum mechanical model of the atom uses complex shapes of orbitals (sometimes called electron clouds), volumes of space in which there is likely to be an electron. So, this model is based on probability rather than certainty.