The classification of matter divides all substances into elements, compounds, or mixtures. Determining whether a substance is an element or a compound depends entirely on the types of atoms it contains and how they are arranged. Scientists rely on the atomic structure of a substance to determine its proper category. This classification is essential for predicting how any material will behave and interact with other substances.
Defining Elements
An element is defined as a pure substance made up of only one type of atom. It cannot be broken down into simpler chemical substances through ordinary chemical reactions. All atoms within a single element share the same number of protons, known as the atomic number, which gives each element its unique identity and placement on the periodic table (e.g., Gold (Au), Carbon (C), or Oxygen (O)).
Although the definition focuses on a single type of atom, many elements naturally exist as molecules rather than isolated atoms. This is true for diatomic elements, where two atoms of the same element are chemically bonded together. For instance, the oxygen we breathe is found as O2, and nitrogen in the atmosphere exists as N2.
Defining Compounds
A compound is a pure substance formed when two or more different elements are chemically bonded together in a fixed ratio. For example, water (H2O) consists of two hydrogen atoms bonded with one oxygen atom. This fixed composition is a defining characteristic, meaning the ratio of atoms must remain constant regardless of the sample size.
The properties of a compound are distinctly different from the properties of the individual elements that combine to form it. For example, hydrogen and oxygen are gases, but when they chemically combine, the resulting compound, water, is a liquid. This change in characteristics confirms that a chemical reaction has occurred, forming a new substance. Unlike elements, compounds can be broken down into their constituent simpler elements using chemical methods.
Classification of Br2
The chemical formula Br2 represents Bromine, which has an atomic number of 35. The subscript “2” indicates that this molecule consists of two Bromine atoms bonded together.
Based on the scientific definitions, Br2 is classified as a molecular element. It consists exclusively of Bromine atoms, satisfying the requirement that an element contains only one type of atom.
Bromine is one of the seven elements that naturally occur as a diatomic molecule in its pure form. At room temperature, elemental Bromine (Br2) is a volatile, reddish-brown liquid, making it the only non-metal element to exist as a liquid under standard conditions.