An element is defined by the IUPAC as a pure chemical substance composed of atoms with the same number of protons in the atomic nucleus. All atoms of an element have the same number of protons.
| Fact to Remember | Name of the Element |
| Atoms of elements can have different number of electrons and neutrons. | |
| A variant of an element with different number of neutrons is known as its | Isotope |
| Different physical form of an element is known as its (e.g. graphite and diamond) | Allotrope |
| Element most abundant in the Universe | Hydrogen |
| Element most abundant in the human body | Oxygen |
| Element which forms more than 10 million compounds | Carbon |
| Element with the lowest melting and boiling point | Helium |
| Element with the highest melting point | Carbon |
| Element with the highest boiling point | Tungsten |
| Element with highest density | Osmium |
| Element with lowest density | Hydrogen |
| Element with highest electronegativity | Flourine |
| Element with lowest electronegativity (highest electropositivity) | Francium |
| The first element to be produced artificially | Technitium |
| The most corrosion resistant element (which cannot be affected by water, chemicals or acids) | Iridium |
| The element which was discovered on the Sun before it was found on the Earth | Helium |
| The non-metallic element which is liquid at room temperature | Bromine |
| The metallic element which is liquid at room temperature | Mercury |
| The most reactive element | Flourine |