Presentation on theme: "Electrons in Atoms. Models of the Atom 5.1.1 – I can identify the inadequacies in the Rutherford atomic model. 5.1.2 - I can identify the new proposal."— Presentation transcript:
5.1.1 – I can identify the inadequacies in the Rutherford atomic model. 5.1.2 - I can identify the new proposal in the Bohr model of the atom. 5.1.3 - I can describe the energies and positions of electrons according to the quantum mechanical model. 5.1.4 - I can describe how the shapes of orbitals related to different sub-levels differ.
Elements Elements Rutherford’s atomic model couldn’t explain the chemical properties of elements.
You may need to use your book to fill this in – Pages 128-129
Niels Bohr (Danish 1885- 1962) a student of Rutherford saw that his model needed improvement. Bohr proposed that an electron is found only in specific circular paths, orbits, around the nucleus. Energy levels – the fixed energies an electron can have.
Energy levels are like steps or rungs on a ladder. Quantum – amount of energy required to move an electron from one energy level to another energy level. Energies between levels are not all the same
Erwin Schrödinger (Austrian 1887-1961) used math to describe the behavior of the electrons. Quantum mechanical model – modern description of electrons in atoms based on mathematical solutions to the Schrödinger equation.
The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus. Think of as a fuzzy cloud of chance.
Atomic orbitals – a region of space in which there is a high probability of finding an electron. Distinguished by n (principle quantum number or energy level) and a number (n = 1, 2, 3…)
In each energy level there are orbitals (shapes) called sublevels. Each energy sublevel corresponds to a different shape, which describes where the electron is likely to be found.
5.2.1 - I can describe how to write the electron configuration for an atom. 5.2.2 - I can explain why the actual electron configurations for some elements differ from those predicted by the aufbau principle.
Electron configuration – way in which electrons are arranged in atoms. Three rules – the aufbau principle, the Pauli exclusion principle, and Hund’s rule – tell you how to find the electron configuration.
Aufbau principle – states that electrons occupy the orbitals of lowest energy first. Orbitals on any sublevel are always the same energy.
Pauli exclusion principle – an atomic orbital may describe at most two electrons. When electrons pair they must have opposite “spins” so they don’t repel as much.
Hund’s rule – electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible. Basically singles in a sublevel until they have to double up.
Shorthand for these are: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 …
Some actual electron configurations differ from those assigned using the aufbau principle because half-filled sublevels are not as stable as filled sublevels, but they are more stable than other configurations.