Ease of reaction of hydrogen with alkali and alkaline earth metals

1. [![enter image description here](https://i.stack.imgur.com/c4UNY.png)](https://i.stack.imgur.com/c4UNY.png)


The ease of reaction of group 1 metals with hydrogen decreases as we
go down the group.


2. [![enter image description here](https://i.stack.imgur.com/17Lhj.png)](https://i.stack.imgur.com/17Lhj.png)


But why lithium requires high temperature than sodium, potassium and
rubidium?


3. [![enter image description here](https://i.stack.imgur.com/yoC46.png)](https://i.stack.imgur.com/yoC46.png)


What is exactly "ease of reaction"? I think it is related to kinetics (rate) of reaction and not related to thermodynamics of reaction. If so, is there any chemical data table from which I can predict the ease of reaction for group 2 metals with hydrogen?


Also, at what temperature, the ease of reaction should be compared?


The following processes involve in formation of $\ce{MH(s)}$ from $\ce{M(s)}$ and $\ce{H2(g)}$:


$$\ce{M(s)\rightarrow M(g)\rightarrow M+(g)}$$
$$\ce{1/2H2(g)\rightarrow H(g)\rightarrow H-(g)}$$
$$\ce{M+(g) + H-(g)\rightarrow MH(s)}$$


I know that it can be done by measuring and then comparing the formation of products over time, i.e. $\ce{\frac{\Delta [MH]}{\Delta $t$}}$.


**References:**


1. Page 297, Concise Inorganic Chemistry, 5E, J. D. Lee (Wiley)
2. Page 115, Descriptive Inorganic Chemistry, 3E, House (Elsevier)
3. Page 342, Concise Inorganic Chemistry, 5E, J. D. Lee (Wiley)


