You find a compound composed only of element "x" and hydrogen, and know that it is 91.26% element x by mass. each molecule has 2.67 times as many h atoms as x atoms. what is element x?

The element X is silicon.

Explanation:

Percentage of element X in compound molecule = 91.26%

Number of X element atom in a molecule = n

Number of hydrogen atom in a molecule = n × 2.67

Molecular formula of compound =

Let the atomic mass of element X = m

Molar mass of compound =

Percentage of an element in a compound:

m = 27.87 g/mol ≈ 28 g/mol

The element X is silicon.

it's c. elements are placed in rows based on how may valencies electrons have.