The atomic number of an element is 11. Its electronic configuration is: MCQ with Answer and Explanation

Explanation:
J.J. Thomson proposed the 'Plum Pudding' model in 1904 after discovering the electron. He envisioned the atom as a sphere of positive charge with negatively charged electrons embedded within it, like plums in a pudding. This was later disproved by Rutherford's gold foil experiment.

Explanation:
According to the law of conservation of mass, the mass of a substance remains constant during any physical change, including the interconversion of states. Density, volume, and shape change as the intermolecular spaces and arrangement alter during phase transitions, but the total number of atoms and mass is conserved.

Explanation:
Elements in the same group (vertical column) have the same number of valence electrons, resulting in similar chemical properties. For example, all Group 1 elements have 1 valence electron (ns¹). The number of shells increases down the group. Atomic mass varies. This similarity was the basis for Mendeleev's grouping. Modern table uses atomic number for ordering.