VSER They Valence Shell Electron air Repulsion They Electronegativity - describes an atoms desire in a chemical bond to pull electron density to itself. Fluine is the most electronegative atom on the periodic table. It has a greater electron than any other atom in the periodic table. F - F - both fluine atoms have the same desire f electron density so this produces a bond where the electron density is symmetrical on the atoms. Since the electrons are evenly distributed this molecule is said to be NON-OLR. C - F - since the atoms are different they will have different electronegativities. The fluine is the most electronegative atom so the electrons will tend to shift towards the fluine atom. This creates a dipole moment in the molecule. One side of the atom is me negative that the other. Since this molecule has electrons unsymmetrically located it is called a OLR molecule. WRNING: Looking f a dipole moment is not the only fact to consider when trying to determine if a molecule is polar not. You must consider the symmetry of the molecule. : The linear molecule HgCl2 Cl - Hg - Cl The HgCl2 molecule has 2 dipole moments. Each of the Chline atoms pulls electron density away from the central mercury atom. However the two dipoles are equal in strength and on opposite sides of the atom. Thus, the 2 dipole moments cancel out giving us a NON-OLR molecule. It turns out that anytime there is a high amount of symmetry like this the molecule is non-polar. bbreviations: - Central atom - Terminal atom E - Non-bonded pair of electrons - olar - Non polar N - Not applicable (does not apply in this case)
( s + E s) VSER Fmula atom, icture (pretend every E is an ) Bond ngles (E s are larger than s) (of central atom ) olar / (assume ) (great f testing) 1 N N (if =) (if ) H2 HF if H the central atom 2 CO2, BeCl2, HgCl2, HCN 2 E N sp 1(if =) (if ) N2 NO, CO, CN -1 3 lanar 120 BF3, NO3-1, CO3-2 (ball & stick (must use both wds) 3 2E V-shaped Bent lanar < 120 sp 2 SnCl2, GeCl2, NO2-1, O3 E2 N (if =) (if ) O2 SO
( s + E s) VSER Fmula atom, (ball & stick 4 4 3E icture Tetrahedral Tetrahedron yramidal (must use both wds) Tripodal (pretend every E is an ) Tetrahedral Tetrahedron Bond ngles (E s are larger than s) 109.5 (of central atom ) sp 3 olar / (assume ) < 109.5 (great f testing) CH4, O4-3, CCl4, SnCl4, SiF4 NH3, NCl3, Cl3, H3O +1, NF3 2E2 V-shaped Bent < 109.5 H2O, SCl2, OF2, ClF2 +1, ClO2-1 E3 N (tetrahedrons have four faces and if you put an atom at each cner it has 4 terminal atoms) (if =) (if ) F2, Cl2, Br2, I2 HF if F the central atom
( s + E s) VSER Fmula atom, (ball & stick 5 5 4E 3E2 icture Bipyramidal (must use both wds) Sea-saw Irregular Tetrahedron (4 atoms but warped by non-bonded e - s) T-shaped (pretend every E is an ) Bipyramidal Bipyramid Bond ngles (E s are larger than s) 90 120 <90 <120 < <90 < (of central atom ) sp 3 d d sp 3 olar / (assume ) (great f testing) sf5, Cl5, NbCl5 SF4, TeCl4, ClF4 +1 ClF3 2E3 I3-1, IF2-1, ICl2-1, ef2 (1 of 3 exceptions) E4 N??
( s + E s) VSER Fmula atom, 6 icture Octahedral Octahedron (pretend every E is an ) Bond ngles (E s are larger than s) 90 (of central atom ) olar / (assume ) (great f testing) SF6 (ball & stick 5E Square ydramidal (must use both wds) Octahedral < 90 < TeF5-1, BrF5 6 4E2 3E3 Square lanar (must use both wds) T-Shape Octahedron Tetragonal Bipyramid 90 < 90 < sp 3 d 2 d 2 sp 3 (2 of 3 exceptions) ICl4-1, ef4?? 2E4?? (3 of 3 exceptions) E5 (while it has 6 terminal atoms it gets it s name because it has 8 faces when drawn this way) N??