Chapter U1.11, Problem 3E

Interpretation Introduction

Interpretation:

The evidence which caused Bohr to change Rutherford’s nuclear model is to be described.

Concept introduction:

At the time of Dalton, many scientists have created different models to describe atoms and sub - atomic particles. An atom has a nucleus made of protons and neutrons, with electrons revolving around the nucleus. Some important models are Rutherford’s nuclear mode, Bohr’s model and electron cloud model.

Answer to Problem 3E

Bohr conducted several experiments and found that when elements are exposed to electric fields, certain colors of light are given off. For example, hydrogen atoms give off red, blue - green, and blue light. This evidence made him propose that electrons orbit around nucleus in varying distances like the planets move around the Sun in different orbits.

Explanation of Solution

According to Rutherford’s model of atom, most of atom’s mass was concentrated in the center of the atom which consisted of nucleus. The nucleus was a collection of positively charged particles called protons. The electrons circled around the nucleus. Most of the atom was an empty space.

Bohr improvised Rutherford’s model of atom. He found that when elements are exposed to electric fields, certain colors of light are given off. For example, hydrogen atoms give off red, blue - green, and blue light. This evidence made him propose that electrons orbit around nucleus in varying distances like the planets move around the Sun in different orbits. The electrons in these orbits have different energies. When an electron jumps from an outer orbit to an inner orbit, it gives off a particular color of light depending on the energies of the two orbits.

Bohr’s model is a planetary model in which electrons orbit a small positively charged nucleus just as planets orbit the Sun.

Conclusion

Scientists made observations from several experiments which provided evidence that helped them to make changes and refine the model of atom. Bohr made changes to Rutherford’s nuclear model and proposed planetary model.