Which contribution is a modification to thomson's plum pudding model? a-atoms are indivisible. b-electrons are scattered in an atom. c-a positively charged nucleus sits at the center of an atom. d-atoms of the same element have the same properties.

Answer is: C) A positively charged nucleus sits at the center of an atom.

J.J. Thomson placed two oppositely charged electric plates around the cathode ray. He did experiments using different metals as electrode materials and found that the properties of the cathode ray remained constant no matter what cathode material he used.

Tomson concluded that atoms are divisible and that the corpuscles are their building blocks (atoms are made up of smaller particles).  

J. J. Thomson discovered the electron in 1897.  

His "plum pudding" model (1904) suggested: the electrons are embedded in the positive charge.  

With this model, he abandoned his earlier hypothesis (the atom was composed of immaterial vortices).  

Rutherford theorized that atoms have their charge concentrated in a very small nucleus.

This was famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).  

Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.

That is different from Plum Pudding model, because it shows that most of the atom is empty space.

C-A positively charged nucleus sits at the center of an atom.

Explanation:

The 'plum-pudding' model was put forth by J.J Thomson to explain the structure of an atom. According to the model, the electrons which are negatively charged particles are essentially dispersed in cloud of positive charges. This was later modified by his student Rutherford through the goil foil experiment.

Rutherford's experiment essentially suggested that the positive charges are concentrated in a core or the center of an atom while the electrons move around it in fixed orbits.

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