Orbital filling electron configuration Hunds rule electrons fill

Orbital filling & electron configuration Hund’s rule: electrons fill one at a time Pauli’s exclusion principle: opposite spin Configuration & the periodic table

Shells with orbitals A simple modification of Bohr’s model allows us to see one effect of orbitals on the configuration of electrons around the nucleus. 3 d Shells Subshells #e- e- pairs 1 s 2 1 3 p 2 s 2 1 2 p 3 s p 6 3 1 s /n 2 s 3 s p d p. 228 - 2 1 6 3 10 5 Notice that each subshell (or orbital) can only hold a max of 2 electrons. How many electrons in an atom? Atomic # Which is the valance shell? Outermost; here 3 rd shell What causes chemical bonding? Overlapping, or interaction, of electrons in valence shells of 2 atoms.

Orbital energy levels The energy levels of orbitals increase in a straightforward manner until we reach the junction of the 3 rd & 4 th shells. This table shows which orbitals are filled for each column of elements. 1) electropositive metals (IA, IIA) 2) transition metals (d orbitals) 3) non-metals (& metalloids) (other As) p. 232 -4, 240

Orbital diagrams p. 235 Notice that the orbital ‘boxes’ fill one electron (e-) at a time. What property of eexplains their desire to be ‘alone’? Negative charge -> repulsion. Notice that the two e- occupying an orbital have opposite ‘spin’. Electron spin creates magnetic fields, minimized by opposite spin. Two e- with opposite spin are ‘paired’.

Orbital filling: Aufbau H Li Na K Rb Cs Fr He 1 s 2 2 p 6 3 s 2 3 p 6 Ne Ar 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 6 Kr Xe 6 s 2 4 f 14 5 d 10 6 p 6 7 s 2 5 f 14 6 d 10 7 p 6 Rn ? ? p. 233

Examples: orbital filling Draw the orbital diagram for oxygen. O is element 8: 1 s 22 p 4 Draw the electron configuration of phosphorous. Atomic number 15: 1 s 22 p 63 s 23 p 3 Notice that three of the electrons are unpaired. What valence electron configuration is common to all halogens? Halogens are the elements found in column VIIA. Their valence (or outermost) electron shell has 7 ve- (column number). Let’s try them: F #9 1 s 22 p 5 Cl #17 1 s 22 p 63 s 23 p 5 Br #35 1 s 22 p 63 s 23 p 64 s 23 d 104 p 5 I #53 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 5 So the common valence configuration is p 5. Soon, we’ll see that all halogen ions have a charge of -1 to fill that p orbital. p. 235 -

Electron configuration & the periodic table p. 242