NCERT Solutions for Class 12 Physics Chapter 13 Nuclei

Nucleus (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to the Atomic nucleus, the very dense central region of an atom—cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA. In every atom, the positive charge and mass are densely concentrated at the centre of the atom forming its nucleus. More than 99.9% mass of the atom is concentrated in the nucleus. The nucleus is a collection of particles called protons, which are positively charged, and electrically neutral neutrons. Protons and neutrons are in turn made up of particles called quarks.