Answer: I'm not sure what your question is but i'll answer as best as I can.
Explanation:
Since X is equal to 7 H and we know that H is equal to 1.008, we can just do 7x1.008 = 7.056 g. I hope i helped and please clarify more in the future.
The atomic mass of an element is given by the sum of the mass of protons and neutrons. The element X is lithium as it has a mass of 6.941 u.
Atomic mass is the sum of the masses of the isotopes of that element and is given by adding the masses of the number of protons and neutrons of the elemental atom.
The atomic mass of one hydrogen atom is 1.008, so seven hydrogens will be, 7 x 1.008 = 7.056 g. Now, from the periodic table, it can be seen that an atomic mass of 7.056 g is closest to the atomic mass of a lithium atom (6.941 u).
From the mass, it can be said that seven hydrogen atom has an equivalent mass as that of one lithium atom in the periodic table. The lithium atom has atomic number 3 and an atomic mass of 6.941 g/mol.
Therefore, element X is lithium.
Learn more about atomic mass here:
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