Bohr's model

Understanding Atomic Structure: Bohr’s Model

Atoms are the fundamental units that make up all the substances in our surroundings. To understand how these tiny particles interact and form different types of matter, scientists introduced several theories about their internal structure. Among them, one significant model was introduced by Niels Bohr.

What is Atomic Structure?

The atomic structure describes the arrangement of particles — protons, neutrons, and electrons — inside an atom. Protons and neutrons are found in the center of the atom (called the nucleus), while electrons move around the nucleus in fixed paths called shells or orbits.

Bohr’s Model of the Atom

In 1913, Niels Bohr gave a model that improved upon earlier ideas about atoms. His model is widely taught because it explains many atomic behaviors in a simple way.

Main Features of Bohr’s Model:

• Electrons move around the nucleus in defined circular orbits, which are known as shells or energy levels.
• These shells are labeled as K, L, M, N or numbered as 1, 2, 3, 4, and so on.
• Every energy level contains a specific amount of energy, and electrons retain that energy while orbiting without losing it.
• Electrons can shift to a higher energy level by taking in energy or return to a lower one by giving off energy.

Shell Capacity (Bohr–Bury Rule):

The maximum number of electrons that can be held in each shell is given by the formula: 2n², where n is the shell number.

• K shell (n = 1): 2 × 1² = 2 electrons
• L shell (n = 2): 2 × 2² = 8 electrons
• M shell (n = 3): 2 × 3² = 18 electrons

Example: Atomic Structure of Sodium (Na)

The atomic number of sodium is 11, which means it contains 11 protons and 11 electrons. That means it has 11 protons and 11 electrons. According to Bohr’s model:

• K shell holds 2 electrons
• L shell holds 8 electrons
• M shell holds 1 electron

The electronic arrangement of sodium is 2 electrons in the first shell, 8 in the second, and 1 in the outermost shell (2, 8, 1).

Importance of Bohr’s Model

• Explains how electrons are arranged in atoms
• Introduced energy levels or shells
• Helps predict how atoms will react with each other

Conclusion

Bohr’s model of the atom was a major step in understanding atomic structure. It gave us a clearer picture of how electrons are arranged and how atoms interact. This knowledge forms the foundation of modern chemistry and helps explain many chemical properties of elements.