أرشيف الوسم : Atoms

ATOMS THREE POSTULATES OF DALTON’S ATOMIC THEORY 1) An element is composed of identical atoms. 2) Atoms of different elements have different properties. 3) Compounds are atoms of 2 or more elements chemically combined. THE LAW OF CONSERVATION OF MASS During a physical change or reaction, or a chemical reaction, matter is neither created nor destroyed. (Lavoisier – 1777) THE …

Atomic nucleus The central region of an atom. Atoms are composed of nega­tively charged electrons, positively charged protons, and electrically neutral neutrons. The protons and neutrons (collectively known as nucleons) are located in a small central region known as the nucleus. The electrons move in orbits which are large in comparison with the dimensions of the nucleus itself. Protons and …