Rubidium has 37 elections. there are multiple other sources you could use too confirm this. :-)
Methane's formula is CH4 I don't get the question but if those are the quantities of 1 of those metals, that means that you don't have enough grams of carbon. You will need 5g x 4 = 20grams of carbon.
Hope that's what you were looking for.
Answer: The solution to the problem expressed to he correct number of significant figures is 1.69
Explanation:
Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.
The rule applied for multiplication and division is :
The least precise number determines the number of significant figures in the answer.
As 12.0 has 3 significant digits and 7.11 also has 3 significant digits, the answer would also contain 3 significant digits.
For 
Thus the solution to the problem expressed to he correct number of significant figures is 1.69
It has ns1 electron configuration like the alkali metals.