What are key characteristics of elements?

Elements are characterised by their atomic number, atomic mass, electron configuration, and physical and chemical properties.

Each element is defined by its atomic number, which is the number of protons in the nucleus of an atom. This number is unique to each element and determines its position in the Periodic Table. For example, hydrogen has an atomic number of 1, helium has an atomic number of 2, and so on. The atomic number is also equal to the number of electrons in an atom, which influences the element's chemical behaviour.

The atomic mass of an element is another key characteristic. It is calculated by adding the number of protons and neutrons in an atom. While the number of protons remains constant for a given element, the number of neutrons can vary, leading to different isotopes of the same element. For instance, carbon-12 and carbon-14 are isotopes of carbon with different atomic masses.

The electron configuration of an element, which describes the distribution of electrons in an atom's electron shells, is another defining characteristic. The electron configuration determines the chemical reactivity of an element, as it is the electrons in the outermost shell that are involved in chemical reactions. For example, elements in Group 1 of the Periodic Table (like sodium and potassium) have one electron in their outermost shell, making them highly reactive.

Lastly, elements are characterised by their physical and chemical properties. Physical properties include characteristics like melting point, boiling point, density, and appearance. Chemical properties describe how an element reacts with other substances. For example, metals (like iron and copper) are good conductors of heat and electricity, while non-metals (like oxygen and nitrogen) are poor conductors. Some elements, like noble gases (helium, neon, argon etc.), are very unreactive due to their full outer electron shells.

In summary, the key characteristics of elements include their atomic number, atomic mass, electron configuration, and physical and chemical properties. These characteristics help scientists categorise and understand the behaviour of different elements.