Jj thompson developed the plum pudding (blueberry muffi/chocolate chip cookie) model of the atom he is credited with disvcovering which subatomic particle

proton
neutron
nucleus
electron

Electron

Explanation:

His model discovers the negatively charged electrons

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.