Which was a testable idea that ernest rutherford developed in his experiments?
- the positive charge in an atom is concentrated in one location.
- atoms are not divisible into smaller particles.
- it is impossible to define the mass of an atom.
- the atom contains no particles that have a neutral charge.

- The positive charge in an atom is concentrated in one location.

Explanation:

In Rutherford's experiment when alpha particles are projected towards the gold foil then he observed that major proportion of the alpha particles are moved out undeviating.

This shows that alpha particles which are positively charged are not repelled by other positive charge of nucleus as it is concentrated at small part of atom

because very few alpha particles are reflected back at 180 degree so he concluded that nucleus charge is concentrated at very small space

and that part is termed as nucleus.

so correct answer is

- The positive charge in an atom is concentrated in one location.