Electron Orbitals Cartoon courtesy of lab-initio.com
Quantum Mechanical Model of the Atom The model says that the nucleus is surrounded by a space in which electrons orbit- the electron cloud.
The model says that the electron cloud is divided the following parts: 1) The electron cloud is divided into energy levels (n) numbered 1,2,3,4, to infinity( ) 2) Each energy level is divided into sublevels. 3) Each sublevel is divided into orbitals. Regardless of which energy level it resides, sublevel s has 1 orbital. Sublevel p has 3 orbitals. Sublevel d has 5 orbitals. Sublevel f has 7 orbitals. (Note: the pattern continues to go up by odd numbers.) 4) Each orbital can hold a maximum of 2 electrons with opposite spins.
1) Electron Energy Levels The electron cloud is divided into energy levels (n) numbered 1,2,3,4, to infinity( ) n1 is closest to the nucleus. The farther out from the nucleus the more energy the level has.
1) Electron Energy Levels n is also known as the Principle Quantum number Formula to find the total number of electrons that can fit in an energy level: 2n 2 n 1 is closest to the nucleus.
2) Each energy level is divided into sublevels. -Level 1 has 1 sublevel (s). -Level 2 has 2 sublevels (s,p). - Level 3 has 3 sublevels (s,p,d). -Level 4 has 4 sublevels (s,p,d,f). Sublevels continue to be labeled with letters. After s,p,d,f they just go through the rest of the alphabet (g,h,i, etc.).
3) Each sublevel is divided into orbitals.
What is an Electron Orbital? An orbital is a region within an energy level where there is a probability of finding an electron. Orbital shapes are defined as the surface that contains 90% of the total electron probability.
Scientists can not draw the path the electrons take in the orbital because.. To plot a path for something you need to know exactly where the object is and be able to work out exactly where it's going to be an instant later. You can't do this for electrons.
Heisenberg Uncertainty Principle One cannot simultaneously determine both the position and momentum of an electron. You can find out where the electron is, but not where it is going. Werner Heisenberg OR You can find out where the electron is going, but not where it is!
Orbital shapes Regardless of which energy level it resides, sublevel s has 1 orbital. Sublevel p has 3 orbitals. Sublevel d has 5 orbitals. Sublevel f has 7 orbitals. (Note: the pattern continues to go up by odd numbers.)
Electron Spin 4) Each orbital can hold a maximum of 2 electrons with opposite spins. Electron spin describes the behavior (direction of spin) of an electron within a magnetic field. Possibilities for electron spin: Forward, backward
Pauli Exclusion Principle Two electrons occupying the same orbital must have opposite spins Wolfgang Pauli
Principles of electron configurations: 1) Aufbau Principle: Electrons enter the orbital of the lowest energy level first. 2) Hund s Rule: Electrons enter the orbital of equal energy and then pair up. 3) Pauli Exclusion Principle: Two electrons occupying the same orbital must have opposite spins
Orbital filling table
Electron configuration of the elements of the first three series
Element Atomic # Configuration notation Orbital notation Noble gas notation Lithium, 3 p+= 3 e- = 3 1s 2s 2p Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neo 1s 2s 2p 1s 2s 2p 1s 2s 2p 1s 2s 2p 1s 2s 2p 1s 2s 2p 1s 2s 2p
Periodic Trends Blocks can be grouped according to the sublevels s block Group 1A ands 2A p block Group 3A through 8A d block the transition metals/elements f block the Inner Transition Metals
So what this says is that it is impossible to plot the path of an electron around the nucleus!
Practice Then a few more things.
Examples Row number = period = energy level Hydrogen- row 1= period 1, block 1s H-1s 1 Beryllium row 2 =period 2, block 2s Be- 1s 2 2s 2 Carbon row 2 =period 2, block 2p C- 1s 2 2s 2 2p 2
The Exceptions! 1. Transition elements (d sublevel)- The energy level is 1 less than the row/period # Ex: Sc- period 4d but it will end in 3d! Sc- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 2. Inner transition metals (f sublevel)- The energy level is 2 less than the row /period # Ex: Dy- period 6f but it will end in 4f! Dy- 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4P 6 5s 2 4d 10 5p 6 6s 2 4f 9