Analyzing Thomson's Atomic Model Statements

This question asks us to identify the correct statements about J.J. Thomson's model of the atom, often called the "plum pudding" model.

Understanding Thomson's Model

Thomson proposed his model in 1904, shortly after discovering the electron. His key ideas were:

• An atom is a sphere of uniformly distributed positive electricity.
• Electrons, which are negatively charged particles, are embedded within this positive sphere.
• The negative electrons and the positive sphere balance each other out, making the atom electrically neutral.

Evaluating Each Statement

Statement i: Atoms consist of a positively charged sphere.

According to Thomson's model, the atom was visualized as a sphere of positive charge. This statement accurately reflects that concept.

Result: Correct.

Statement ii: Electrons are randomly moving outside the sphere.

In Thomson's model, electrons are embedded *within* the positively charged sphere, not moving randomly outside of it. They are stationary parts held within the positive substance.

Result: Incorrect.

Statement iii: The number of positive and negative charges is equal.

Thomson suggested that the atom as a whole is electrically neutral. To achieve this neutrality, the total negative charge of the embedded electrons must be equal to the total positive charge of the sphere.

Result: Correct.

Statement iv: The atom is overall neutral.

This statement is a direct consequence of statement (iii). Because the positive charge of the sphere and the negative charge of the electrons are equal in magnitude, they cancel each other out, resulting in a neutral atom.

Result: Correct.

Conclusion on Statements

Based on the analysis, statements (i), (iii), and (iv) are correct descriptions of Thomson's atomic model. Statement (ii) is incorrect as electrons are described as embedded within, not moving outside, the sphere.

Identifying the Correct Option

The option that includes the correct statements (i), (iii), and (iv) is the correct answer.

• Option 1: (i), (ii), and (iii) only - Incorrect (ii is wrong).
• Option 2: (ii) and (iii) only - Incorrect (ii is wrong, i and iv are missing).
• Option 3: (i), (iii), and (iv) only - Correct (Matches our analysis).
• Option 4: (i), (ii), (iii), and (iv) - Incorrect (ii is wrong).