超一流化学高手、化学专家请进(Periodicity0017)(a)Statetwophysicalcharacteristicsofthealkalimetals.(b)Lithium,sodiumandpotassiumarealkalimetals.Explainthefollowingtrends.(1)Potassiumhasthelargestatomicradiuswhilel

Question

超一流化学高手、化学专家请进(Periodicity 0017)
(a) State two physical characteristics of the alkali metals.
(b) Lithium,sodium and potassium are alkali metals.
Explain the following trends.
(1)Potassium has the largest atomic radius while lithium
has the smallest.
(2)Potassium has the smallest ionization energy while lithium
has the largest.
(3)The melting point of lithium is the higest and that of
potassium is the lowest.
(4)The hydration energy of lithium is the largest while that
of potassium is the smallest.
(c) Compare the atomic radius,ionization energy,melting point and hydration energy of the alkaline earth metals to their corresponding alkali metals in the same period.
Thanks.

Answer 1

(a) 1.Low melting point
2.Low electric conductivity
3.Low density
(b) 1.According to periodicity,within a same group (IA in the case of alkali metals),atomic radius increases from top to bottom because more valance levels are filled.
2.According to periodicity,within a same group (IA in the case of alkali metals),ionization energy decreases from top to bottom because the single valence electron is less tightly bond to the nucleus.
3.In alkali metal group,melting point decreases from top to bottom becasue the stabilty of metal bond,which is formed by s1 valence electrons,decreases when valence level increases.
4.Because lithium ion has the smallest radius,and thereby the strongest ability to polarize water molecule to give the largest hydration energy.
(C)atomic radius:alkali metals>alkaline earth metals
ioniztion energy:alkali metals