Electron configuration and chemical reactivity A study of the alkali metals family HW 8-14

Link to alkali metals

Reaction with O2 in air Lithium Cesium Rapid “rusting” (oxidation) Spontaneously combusts Cesium Cesium oxide

Reaction with water Lithium Cesium

Comparison of Alkali Metals 1) Similar: All are shiny, silvery, soft metals All react rapidly with O2. Surface oxidizes to black quickly. All react vigorously with water to produce H2 gas.

Comparison of Alkali Metals 1) Different How quickly and vigorously reaction occur vary between different metals Lithium Sodium Cesium

Li [Ne]3s1 [Kr]5s1 [Xe]6s1 Element Na K [Ar]4s1 Rb Cs e- configuration Reactivity Rank Li [He]2s1 5 Na [Ne]3s1 4 K [Ar]4s1 3 Rb [Kr]5s1 2 Cs [Xe]6s1 1

As we move down the family, the reactions seem to become “TERRIFYING” Lithium Cesium

3) All members of the family have similar electron configuration, ns1, one valence electron. 4) If they lose 1 valence e-, they will have a completely filled valence level.

Things seem to become more terrifying as we move down the group Link to alkali metals MOST REACTIVE LEAST REACTIVE

Strength of Attraction between + and – charges depends upon distance + +

Strength of Attraction between + and – charges depends upon distance + + Li Cs Li positive nucleus has a stronger attraction to its 2s valence electron because 2s orbital is closer to nucleus than 6s electron is to nucleus of Cs.

Comparing Li vs Cs Similarities Differences Shiny, metallic, solids Li: [He]2s1 Cs: [Xe]6s1 Similarities Differences Shiny, metallic, solids Highly reactive M + O2 → M2O M + H2O → H2 + MOH Explanation: Li and Cs both have s1 electron configuration Want to lose 1 e- to obtained filled valance electron energy level “Things seem to become more terrifying (reactive) as we move down the group” Reactivity: Cs >> Li Size increases as we move down the group Atomic radius: Cs >> Li Explanation: Cs’s Valence electron in 6s orbital is much farther from nucleus and therefore more weakly attracted than electron in 2s orbital for Li.

Which is more reactive F or I? Fluorine, element #9 Iodine, element #53 Electron configuration: [He]2s22p5 Gain, Lose or share to fill valence electron level? Need to gain 1 e- to obtain filled valence electron level. Relative size? I >> F Electron configuration: [Kr]5s2 4d105p5 Gain, Lose or share to fill valence electron level? Need to gain 1 e- to obtain filled valence electron level. Relative size? I >> F Which is more reactive F or I?

Which is more reactive F or I ? Video link F is more reactive with a smaller radius because it will have a stronger attraction to pull in an electron because the valence electron level is closer to the nucleus e- e-

Reaction of Cesium and Fluorine Link to reaction of Cs and F