Answer :
Answer:
Hydrogen and Oxygen
Explanation:
Hydrogen atomic mass = 1.008 amu
atomic mass = 15.999 amu
According to the periodic table, two elements whose atomic mass is less than twice their atomic number are hydrogen and oxygen.
The atomic number of an atom refers to the number of protons in that atom. It serves as an identity for atoms of elements. The atomic mass of element is the weighted average of the masses of all the isotopes of the element.
The atomic number of oxygen is 8 while the atomic number of hydrogen is 1. The atomic mass of oxygen is 15.999 amu while the atomic mass of hydrogen is 1.0008 amu.
We can see that twice the atomic number of oxygen gives sixteen while twice the atomic number of hydrogen gives two. Therefore, two elements whose atomic mass is less than twice their atomic number are hydrogen and oxygen.
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