STRUCTURE OF ATOM | SPEED NOTES | CBSE | SCIENCE | CLASS 9

Chapter 4- Structure of Atom Summary ofStructure of Atom Ø Ø Atom is the smallest particle of an element. It has two parts: nucleus and outer nuclear part. Nucleus of the atom consists of protons andneutrons. Protons are positively charged particles. Neutrons possess no charge. In outernuclear part, electrons arepresent. Electrons arenegatively charged particles. Atomic number represents the number of protons in an atom. As atoms are electrically neutral, an atom contains as many electrons as it has protons. The total number of protonsand neutrons present in one atom ofan element is known asits mass number. The arrangement of electrons in the various shells/orbits/energy levels of an atom of the element is known as electronic configuration. Atoms of a given atomic number can have different number of neutrons are called isotopes. The atomsof different elements, which have thesame mass number but different atomic numbers are called isobars. These have different number of protons but equal sumof number ofprotons and neutrons. The atomsof different elements, which have thesame number of neutrons butdifferent atomic numbers, are called isotones. Ø Ø Ø Ø Ø Ø