Atomic StructureAtomic Structure
Every substance in the Universe is composed of MATTER. The smallest unit of matter is the ATOM. An atom consists of a central part called the NUCLEUS surrounded by layers of ELECTRONS. The nucleus is made of small particles called PROTONS and NEUTRONS.
One way of imagining an atom is to think of our Solar system with the central Sun surrounded by the Planets, each revolving around the Sun in its own Orbit. The electrons revolving around the nucleus of an atom are in orbits called SHELLS.
The smallest (and simplest) atom is Hydrogen, consisting of one Proton surrounded by one Electron.
Excluding the isotopes, there are 109 types of atoms. Each type of atom is called an ELEMENT. The next most simple element after Hydrogen is Helium with two protons, two neutrons and two electrons.
The structure of an element is indicated by its ATOMIC Number and MASS Number. The Atomic number is the number of Protons. The Mass number is the total number of Protons plus Neutrons.
In a normal atom the number of Electrons is equal to the number of Protons.
Element |
Symbol |
Atomic Number |
Mass Number |
Number of Protons |
Number of Neutrons |
Number of Electrons |
| Hydrogen | H | 1 | 1 | 1 | 0 | 1 |
| Helium | He | 2 | 4 | 2 | 2 | 2 |
| Lithium | Li | 3 | 7 | 3 | 4 | 3 |
| Beryllium | Be | 4 | 9 | 4 | 5 | 4 |
| Boron | B | 5 | 11 | 5 | 6 | 5 |
| Carbon | C | 6 | 12 | 6 | 6 | 6 |
| Nitrogen | N | 7 | 14 | 7 | 7 | 7 |
| Oxygen | O | 8 | 16 | 8 | 8 | 8 |
| Fluorine | F | 9 | 19 | 9 | 10 | 9 |
| Neon | Ne | 10 | 20 | 10 | 10 | 10 |
Atomic Structure - QUIZ