The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.
<h3>Answer:</h3>
Phosphoric acid reacts with magnesium hydroxide to produce magnesium phosphate and water via the following reaction:
2H3PO4 + 3Mg(OH)2 → Mg3(PO4)2 + 6H2O
(solid) (solid) (solid) (liquid)
<h3>Explaination:</h3>
This is a typical neutralization reaction of an acid with a base to form a salt and water. The reaction is exothermic, gives off heat,
ΔH < 0 , and may be balanced by adding balancing numbers in front, ie adding molecules, in order to ensure that the total number of atoms of each element is the same on the left and right hand sides of the equation.
Doing so we obtain :
2H3PO4 + 3Mg(OH)2 → Mg3(PO4)2 + 6H2O
(solid) (solid) (solid) (liquid)
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I think it is 11% I read it on a article on msn.
Answer:

Explanation:
The number of valence electrons tells us the group number of the neutral atom.
The atom has 4 valence electrons.
The atom is in group 4.