Final answer:
In the quantum mechanical model of an atom, electrons display both wave-like properties and particle characteristics, and their exact position and velocity cannot be precisely known, only probable, whereas the concept of electrons in fixed orbits is an outdated model.
Step-by-step explanation:
The quantum mechanical model of the atom provides a different perspective on the behavior of electrons compared to classical physics. According to the quantum mechanical model, statement A) 'An electron position and velocity cannot be known exactly, only probable' is true because the exact position and velocity of an electron cannot be determined simultaneously, as described by the Heisenberg uncertainty principle. This principle is at the heart of quantum mechanics and introduces the concept of probability in finding an electron. Statement B) 'The electron can exhibit wave-like properties' is also true. Electrons, according to quantum mechanics, have wave-particle duality, meaning they exhibit properties of both waves and particles. The idea that electrons are found in orbitals, which are regions in space with a high probability of finding an electron rather than fixed orbits, aligns with this principle. Statement C) 'An electron is found in an orbit, like a planet orbiting the sun' is false in the context of the quantum mechanical model since it refers to the outdated Bohr model, which has been superseded by the more accurate quantum model. Therefore, choices A and B are correct, making D) 'Two of the above are true' the accurate answer.