Question

The most abundant element in the universe is thought to be :
A . Hydrogen
B . Carbon
C . Oxygen
D . Nitrogen

Answer 1

Hint : The most abundant element in the universe is thought to be Hydrogen . The reason behind its abundance in the universe is hydrogen structure . The electrically neutral atom contains a proton which has positive charge and an electron of negative charge . It is represented by the symbol $H$ .Atomic mass of Hydrogen is $1.007$u and atomic Number is $1$ .

Complete answer:
> Hydrogen is made up of one proton and one electron (in the periodic table this is the only element without a neutron ). Hydrogen is the simplest element present in the universe. The second most abundant element in the universe is Helium, but still there is ten times more hydrogen than helium in this universe . Hydrogen and Helium make up three quarters of known matter in the universe. So it is concluded by the scientist that the elements which have the higher atomic mass are less abundant in the universe. So the molecule of hydrogen is the simplest molecule in the universe. Hence option A is correct which is Hydrogen .

Note : Hydrogen has a single shell so electrons lie in the last shell (valence shell) .It shares similarities with elements in group I-A that are alkali metals. It is a strong reducing agent like other alkali metals. It also shows similarities with the halogen family .Hydrogen also shares the same electronegative nature. Both halogens and hydrogens are diatomic molecules. It combines with metals to form metallic halides as halogen does so. So hydrogen has similarities with alkali metals and halogens.