If the oxide contains 16.99 % o by mass, what is the identity of the metal?

Okay, so let us say that you possess 100g of compound: oxygen is 16.99 grams of it, so this means that we have 16.99 g / 16 g/mol which is equal to 1.062 moles of oxygen.

Considering that you had 16.99 grams of oxygen, then you have: 100 – 16.99 = 83.01 grams of M. We also know that it is two moles per M of oxygen based from the formula. That would mean that you have: 2 x 1.062 moles of M = 2.124 moles of M.

From this, we can conclude that the atomic weight of M is 83.01 / 2.124 = 39.09. The atomic weight that is closest to 39.09 is Potassium.

Therefore, the identity of M is K.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.