The elements in Groups 1 and 2 get more reactive as you go down the group. This means that is more reactive than lithium and is more reactive than beryllium.

Sodium and Magnesium

Explanation:

The elements in Groups 1 and 2 get more reactive as you go down the group.

This means that Sodium is more reactive than lithium and Magnesium is more reactive than beryllium.

On the periodic table, as you go down the group, the reactivity of an element increases. Especially with metals in group 1 and 2. Now Lithium is a metal of group 1, followed by Sodium, while Beryllium is a metal in group 2, followed by magnesium. That's how I picked the answers

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )