Question

What is equivalent hydrogen?

Answer 1

Hydrogen is one of the elements in the periodic table. Hydrogen is the first element in the periodic table. The atomic number of hydrogen is $1$. The symbol of hydrogen is ${\text{H}}$.

Complete step by step answer:
In spatial wise interchangeable hydrogen in the molecule. These interchangeable in spatial means, if change one hydrogen in another hydrogen nothing affects the structure. This kind of hydrogen in the molecule is called equivalent hydrogen.
For, in methane having ${\text{4H}}$ and all are equivalent hydrogen. That means four hydrogen can interchange in their position and nothing affects the molecule.
One more example, methanol. Methanol also has four hydrogen. But out of four hydrogen three only equivalent hydrogen. Because one hydrogen is attached to an oxygen atom. In methanol three hydrogen only spatial in the same environment.
These equivalent hydrogen are predicted by using ${\text{NMR}}$ (nuclear magnetic resonance).
Even isotopes of atoms are also not considered as equivalent hydrogen.

Additional Information: The same atom number but different mass number of the atom is known as isotopes. Hydrogen having three isotopes. There are protium, deuterium and tritium. All the three having the same atomic number is $1$. But the mass number of three isotopes are different. The mass number of protium is $1$. The mass number of deuterium is $2$. The mass number of tritium is $3$. These differences in mass number arise due to the difference in the number of neutrons but the number of protons of all isotopes are the same.

Note: The atomic number of the atom is nothing but the number of protons or number of electrons in the atom. The mass number of the atom is nothing but the sum of the number of protons and the number of neutrons in the atom.