Answer:
D. J. J. Thomson
An atom of calcium
Step-by-step explanation:
J.J. Thomson while carrying out his experiment on the gas discharge tube discovered electrons. He called them cathode rays.
He observed from his experiment that these rays have the following properties;
- they move in a straight line normal to the cathode
- posses kinetic energy and cause the motion of a mechanical paddle
- attract positive charges
From his experiment, he proposed the plum pudding model of the atom where an atom is made up essentially of electrons.
B. The smallest particle of calcium that has all the chemical properties of calcium is an atom of calcium.
It is upon these unit of calcium that the substance calcium is formed. An atom of calcium will show the same properties as a block of calcium.