The chemical element (E) forms the higher oxide E2O, the molar mass of which is 30 g / mol. Name this element.

The molar mass of a substance is defined as the sum of the atomic masses of all elements. The atomic mass of oxygen is 16, let the atomic mass of an element be equal to n.

For E2O oxide, the formula for finding the molar mass will look like this:

M (E2O) = n * 2 + 16

We get an equation with one unknown:

n * 2 + 16 = 30

2n = 30 – 16

2n = 14

n = 14: 2

n = 7

So the atomic mass of our element is 7. In the periodic table with such an atomic mass there is an element lithium – an alkaline monovalent metal. It forms an oxide – Li2O.