Ionic Radii Trend

Sizes of ions: electron repulsion Valence electrons repel each other When an atom becomes a anion (adds an electron to its valence shell) the repulsion between valence electrons increases without changing ENC Thus, F – is larger than F Fluorine atom F 1s 2 2s 2 2p F 1- 1s 2 2s 2 2p 6 +1e Fluorine ionFluoride ion

Atomic Radii Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B IA IIA IIIA IVA VA VIA VIIA = 1 Angstrom IA IIA IIIA IVA VA VIA VIIA = 1 Angstrom Li 1+ Be 2+ Na 1+ Mg 2+ Ba 2+ Sr 2+ Ca 2+ K 1+ Rb 1+ Cs 1+ Cl 1- N 3- O 2- F 1- S 2- Se 2- Br 1- Te 2- I 1- Al 3+ Ga 3+ In 3+ Tl 3+ Ionic Radii

Trends in Atomic and Ionic Size Li Na K 60 Li + 95 Na+ 133 K+ e e e F-F- 136 Cl Br F Cl Br e e e MetalsNonmetals Group 1 Al e e e Group 13 Group 17 Cations are smaller than parent atomsAnions are larger than parent atoms Al 3+

152 Li 60 Li + e Li + e e e e Li Lithium atom Lithium ion Li Lithium atom Li Energy

IA IIA IIIA IVA VA VIA VIIA Li 1+ Be 2+ Na 1+ Mg 2+ Cl 1- N 3- O 2- F 1- S 2- Se 2- Br 1- Te 2- I 1- Al 3+ Ga 3+ In 3+ Tl 3+ Ca 2+ K 1+ Sr 2+ Rb 1+ Cs 1+ Ba 2+ Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba BeBCNOF = 1 Angstrom Atomic Radii Ionic Radii Cations: smaller than parent atoms Anions: LARGER than parent atoms

Isoelectronic Species Oxygen ion O 2- 1s 2 2s 2 2p 6 Fluorine ion F 1- 1s 2 2s 2 2p 6 Sodium ion Na 1+ 1s 2 2s 2 2p 6 Magnesium ion Mg 2+ 1s 2 2s 2 2p Neon atom Ne 1s 2 2s 2 2p 6 Isoelectronic Isoelectronic - all species have the same number of electrons. Can you come up with another isoelectronic series of five elements? Predict the relative ionic sizes within your isoelectronic series. p = 8 n = 8 e = 10 p = 9 n = 9 e = 10 p = 10 n = 10 e = 10 p = 11 n = 11 e = 10 p = 12 n = 12 e = 10