1. Ionic versus Atomic Radius

2. When an atom forms a positive ion (by losing electrons) its radius also changes. 3p e-e- e-e- e-e- e-e- e-e- 13p e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- LiLi 1+ AlAl 3+

3. Ionic versus Atomic Radius When an atom forms a negative ion (by gaining electrons) its radius also changes. 16p e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 9p e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 16p e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- FF 1- SS 2-

4. Cations (positive ions) become smaller than their neutral atoms. Anions (negative ions) become larger than their neutral atoms. Ex. (1) Ca 2+ is ____________________ in size than Ca. Ex. (2) Se is ____________________ in size than Se 2-. Ex. (3) In each of the following pairs, circle which species is the larger. (a) F or F 1- (b) Fe 2+ or Fe (c) Kr or Br Ionic versus Atomic Radius smaller

5. Ex. (4) Rank the following species from largest to smallest: Si, Si 4+, Se, Se 2-, Rn (CONSULT TABLE-S) –Si has a radius of 132 picometers –Se has a radius of 140 picometers –Rn has a radius of 134 picometers Se > Rn > Si Se 2- will be larger than Se and Si 4+ will be smaller than Si Se 2- > Se > Rn > Si > Si 4+ Ionic versus Atomic Radius

6. All atoms absorb energy in order for them to lose an electron. This is an endothermic process. Most atoms release energy in order for them to gain an electron. This is an exothermic process. Ex. (5) Is the reaction, Fe → Fe 2+ + 2 e 1-, endothermic or exothermic? Ex. (6) In the reaction, Fe → Fe 2+ + 2 e 1-, as the atom forms the ion its size  Ex. (7) Is the reaction, Se + 2 e 1- → Se 2-, endothermic or exothermic? Ex. (8) In the reaction, Se + 2 e 1- → Se 2-, as the atom forms the ion its size  Ex. (9) What group of elements is the least likely to gain or lose electrons? Ionic versus Atomic Radius endothermic exothermic decreases increases Noble gases