Electrons & Orbitals

Energy Levels This is the first number in electron configuration. For example, the “2” in “2s1” or the “3” in “3p6” The outermost shells have the most energy. For example, energy level 4 (n=4) has more energy than energy level 3 (n=3) 5 > 4 > 3 > 2 > 1 Energy levels note the relative distance the electron is from the nucleus.

Sublevels Four sublevels exist, denoted by the letters s, p, d, f (mnemonic device _______________________ _____________________________________ ) The energy level (n) corresponds to the number of sublevels in n=1,2,3,&4 For example, when n=1, there is 1 sublevel (s)

Electrons Electrons fill up one sublevel at a time. s can hold 2 electrons p can hold 6 electrons d can hold 10 electrons f can hold 14 electrons

Filling Orbitals Electrons fill orbitals, starting with the lowest energy first. This is called “The Aufbau Principle” For example, 1s (the lowest energy orbital) is filled before 2s (the second lowest energy orbital), and so on…. Energy: 1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s<5f<6d

Electron Orbitals Electron orbitals are one way to show the position of electrons. This has to do with the alignment around the nucleus. Orbital diagrams are drawn with circles, boxes, etc. (the number of boxes is equal to the number of electrons a sublevel can hold/2) s has 1 p has 3 d has 5 f has 7

Electron Orbitals Arrow are used to represent electrons. The direction of arrows indicate their spin (m) Hund’s Rule: when several orbitals of equal energy (subshells) are available, electrons enter with parallel spins first. (the same direction) When filling subshells, place one arrow in each box/circle (these arrows should be in the same direction)    If electrons remain, they may be paired _____ ______ ______

The Pauli Exclusion Principle No 2 electrons can have the same “quantum number” 4 things make up a quantum number…. Energy level (n) Sublevel Alignment/axis Spin So if 2 electrons are both in the 3rd energy level, moving along the figure 8 pattern (p sublevel), and spinning clockwise… Then, they must be moving along different axes (1 on the x-axis and the other on the y-axis, for example)

Electrons

Electrons Note: the higher s and p orbitals fill before the d orbitals. When counting valence electrons, count the electrons on the outer most shell (the highest energy) For example, palladium has a configuration of [Kr] 5s2 4d8 To count the valence electrons only the electrons only the electrons in the highest energy level (in this example n=5) are counted. 2 valence electrons

Electrons The s orbital can contain a maximum of 2 e- The p orbital can contain a maximum of 6 e- Adding the s and p gives a total of 8 possible valence electrons. This is the ideal/stable state Noble gases have a complete valence shell.

Ions Atoms can lose or gain electrons to complete their valence shell (make themselves stable) For example, calcium has an electron configuration of 1s2 2s2 2p6 3s2 the highest energy level is n=3 In n=3, there are 2 valence electrons. (it is easier to lose 2 than gain 6) As a result, calcium will give up its 2 valence electrons. Then, its highest energy level will be n=2 In n=2, there are 8 valence electrons. The resulting ion is Ca2+