Question

Why are there only two elements in the first period of the periodic table?

Answer 1

The first period has less elementsthan any other periods in the periodic table. There are only two elements in the first period: hydrogen and helium. We can explain why there is lesselements in the first row in modern theories of atomic structure. ... Theseelements can only hold two electrons, both in the 1s orbital

Answer 2

There are only two elements in the periodic table that have only one shell.

The periodic table of elements is an arrangement of elements according to increasing atomic number. Metals occur at the left hand side while nonmetals occur at the right hand side.

The groups are composed of elements that have the same number of valence electrons while the periods are composed of elements that have the same number of shells.

Hence, only to elements in the periodic table have one shell; hydrogen and helium. Elements to be placed in period 1 must have only one shell. These two elements are found in the first period for this reason.

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