Answer: Radiation
Explanation: The sun transfers heat energy through radiation since in a vacuum it does not require any medium to allow heat flow.
Strontium element has a mass number of 88 and contains 50 neutrons in the atom.
Given that;
Mass number of element X = 88
Number of Neutrons in element X = 50
we know the concept that Mass number is represent as total number of Neutrons and proton present in Nucleus
So, Mass number of element X = Number of Neutrons in element X + Number of Protons in element X
Thus, 88 = 50 + Number of Protons in element X
Number of Protons in element X = 38
As, Number of proton = Atomic number
So, Atomic number of element X = 38
Hence Unknown Element X is Strontium
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