Question:

What does the negative electronic energy (negative sign for all values of energy) for hydrogen atom means?

Updated On: Jul 7, 2022
  • The energy of an electron in the atom is lower than the energy of a free electron at rest which is taken as zero
  • When the electron is free from the influence of nucleus it has a negative value which becomes more negative
  • When the electron is attracted by the nucleus the energy is absorbed which means a negative value
  • Energy is released by hydrogen atom in ground state
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Solution and Explanation

The energy of the electron in a hydrogen atom has a negative sign for all possible orbits. This negative sign means that the energy of the electron in the atom is lower than the energy of a free electron at rest. A free electron at rest means that is infinitely far away from the nucleus and has the negligible attraction towards the nucleus. Thus it is assigned the energy value of zero. Mathematically, this corresponds to setting the orbit 'n' equal to infinity in the energy equation, such that $E _{\infty}=0$. As the electron gets closer to the nucleus (as n decreases), $E _{ n }$ becomes larger in absolute value and more and more negative. The most negative energy value is given by $n=1$ which corresponds to the most stable orbit. It is called the ground state of an atom.
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Notes on Structure of atom

Concepts Used:

Structure of Atom

Atomic Structure:

The atomic structure of an element refers to the constitution of its nucleus and the arrangement of the electrons around it. Primarily, the atomic structure of matter is made up of protons, electrons and neutrons.

Dalton’s Atomic Theory

Dalton proposed that every matter is composed of atoms that are indivisible and indestructible. 

The following are the postulates of his theory:

  • Every matter is made up of atoms.
  • Atoms are indivisible.
  • Specific elements have only one type of atoms in them.
  • Each atom has its own constant mass that varies from element to element.
  • Atoms undergo rearrangement during a chemical reaction.
  • Atoms can neither be created nor be destroyed but can be transformed from one form to another.

Cons of Dalton’s Atomic Theory

  • The theory was unable to explain the existence of isotopes.
  • Nothing about the structure of atom was appropriately explained.
  • Later, the scientists discovered particles inside the atom that proved, the atoms are divisible.

​​Subatomic Particles

  1. Protons - are positively charged subatomic particles.
  2. Electron - are negatively  charged subatomic particles.
  3. Neutrons - are electrically neutral particles and carry no charge

Atomic Structure of Isotopes

Several atomic structures of an element can exist, which differ in the total number of nucleons.These variants of elements having a different nucleon number (also known as the mass number) are called isotopes of the element. Therefore, the isotopes of an element have the same number of protons but differ in the number of neutrons.  For example, there exist three known naturally occurring isotopes of hydrogen, namely, protium, deuterium, and tritium.