What is atom?

Atoms are the smallest component of matter that determine its unique chemical and physical properties. They are composed of negatively charged electrons, positively charged protons, and electrically neutral neutrons.

A single proton or neutron has a mass of about one atomic mass unit, also referred to as one dalton, after the English scientist John Dalton. One dalton is 1.7 x 10-24 grams. The mass of a proton is 1836 times the mass of an electron, which is approximately 0.0005 daltons.

Although the net electrical charge of an atom is 0, the atom consists of a positively charged nucleus containing neutrons and protons. surrounded by a cloud of negatively charged electrons. The nucleus contains most of the mass of the atom.

Elements are composed of atoms of the same type - with the number of protons, and are organized on the Periodic Table of the Elements. Atoms of an element with different numbers of neutrons are called isotopes, some of which may be radioactive.