Naturally occurring hydrogen consists of three isotopes, hydrogen-1 (1.01 u),
hydrogen-2 (2.02 u) and hydrogen-3 (3.01 u), where the isotopic masses are given in parentheses. use the periodic table and determine which isotope is present in the larger percentage in the natural element.
a. hydrogen-1
b. hydrogen-2
c. hydrogen-3
d. each is present at equal percentages.

Hydrogen-1

Explanation:

Not sure what kind of explanation is needed for your question, because it doesnt specify.

The easiest should be:

Average mass of an element is calculated as the sum of the multiplication of each isotope by its percentage

And the mass of the hydrogen is 1, therefore the more abundant is hydrogen-1

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.