Difference Between Atomic Hydrogen and Nascent Hydrogen

Key Difference – Atomic Hydrogen vs Nascent Hydrogen
 

Hydrogen is a chemical element. It is the first chemical element that can be found in the periodic table of elements (in the group 1, period 1). Each and every chemical element has its own symbol. The chemical symbol of hydrogen is H. Any isotope of hydrogen contains one proton in its atomic nucleus. Hence the atomic number of hydrogen is 1. It is the lightest element that can be found on earth. Atomic hydrogen and nascent hydrogen are two terms used in chemistry to identify the same hydrogen element in different applications. The key difference between atomic hydrogen and nascent hydrogen is that one atom of hydrogen or hydrogen obtained by dissociation of molecular hydrogen is known as atomic hydrogen whereas nascent hydrogen refers to hydrogen that is liberated during a chemical reaction.

CONTENTS

1. Overview and Key Difference
2. What is Atomic Hydrogen
3. What is Nascent Hydrogen
4. Similarities Between Atomic Hydrogen and Nascent Hydrogen
5. Side by Side Comparison – Atomic Hydrogen vs Nascent Hydrogen in Tabular Form
6. Summary

What is Atomic Hydrogen?

Hydrogen obtained by dissociation of molecular hydrogen is known as atomic hydrogen. Hence atomic hydrogen is isolated hydrogen. An atom of hydrogen contains one positively charged proton in the nucleus and a negatively charged electron bound to the nucleus via Coulomb forces. When considering the occurrence of atomic hydrogen, about 70-75% of the normal matter in the universe is atomic hydrogen.

Atomic hydrogen is very rare on earth’s crust because of its high reactivity and energy. Atomic hydrogen tends to form molecular hydrogen (H₂) or other compounds in order to get a lower energy state which is stable.

Atomic hydrogen can be found in three major isotopes. Isotopes are atoms of the same chemical element that have the same number of protons but different numbers of neutrons (or neutrons are absent). There are three major isotopes: Protium, Deuterium and Tritium. Protium has no neutrons in its atomic nucleus; Deuterium has one neutron whereas tritium has two. Protium is the most abundant isotope.

The only electron in atomic hydrogen is occupied in an s orbital. Atomic hydrogen is capable of forming sigma covalent bonds, but not pi bonds since there are no p orbitals. The ionic form of atomic hydrogen is hydrogen ion, which lacks its electron. It is a cation. The chemical symbol for the hydrogen ion is H⁺.

Preparation of Atomic Hydrogen

There are two methods to obtain atomic hydrogen.

Thermal Dissociation Reactions

• Here, molecular hydrogen (H2) is heated to a very high temperature for about 500°C. Then the hydrogen molecules dissociate into atomic hydrogen. However, this is still a theoretical approach.

Electric Discharge Method

• This is done at 0.1 – 1.00 mmHg pressure in an electric discharge tube. The system is operated using molecular hydrogen (hydrogen gas). Tungsten electrodes are used to prepare the electric ark.

What is Nascent Hydrogen?

The term nascent hydrogen is used to call hydrogen that is liberated during a chemical reaction. It is considered that hydrogen liberated during the progression of a chemical reaction is initially in the atomic state; it is then combined to form molecular hydrogen and released as hydrogen gas (or else, this atomic hydrogen will react with some other available ions). For example,

Zn    +    2HCl    →    ZnCl₂   +   2[H]

What are the Similarities Between Atomic Hydrogen and Nascent Hydrogen?

• Both are isolated atomic states of hydrogen.
• Both species are highly reactive and energetic.

What is the Difference Between Atomic Hydrogen and Nascent Hydrogen?

Summary – Atomic Hydrogen vs Nascent Hydrogen

Atomic hydrogen is the isolated form of the chemical element, hydrogen. Nascent hydrogen is also an isolated form of hydrogen. But these two terms are different in their application.  The key difference between atomic hydrogen and nascent hydrogen is that one atom of hydrogen or hydrogen obtained by dissociation of molecular hydrogen is known as atomic hydrogen whereas the term nascent hydrogen is used to call hydrogen that is liberated during a chemical reaction.

Reference:

1. “Atomic Hydrogen” City Collegiate. Available here.
2. “Hydrogen atom.” Wikipedia, Wikimedia Foundation, 18 Feb. 2018, Available here.
3. “Hydrogen.” Wikipedia, Wikimedia Foundation, 18 Feb. 2018, Available here.

Image Courtesy:

1.”Blausen 0526 Hydrogen-1Atom” By BruceBlaus – Own work (CC BY 3.0) via Commons Wikimedia