What is an element defined as?

An element is defined as a substance that cannot be broken down into simpler substances by chemical means. This definition is fundamental to understanding the building blocks of matter. Each element consists of atoms that have the same number of protons in their nuclei, which is characteristic of that particular element.

Elements are the simplest form of matter and serve as the basic materials from which all other substances are made. For example, elements like hydrogen and oxygen exist in their pure forms and cannot be decomposed into anything simpler without losing their unique properties. This is in contrast to compounds, which can be formed from combinations of elements and can be broken down into those elements through chemical reactions.

In the context of the other options, a substance that can be broken down into simpler substances relates to compounds, which consist of two or more different elements chemically bonded together. A combination of two or more elements describes a compound, not an element itself. Similarly, a mixture of compounds refers to physical combinations of substances, which can be separated based on physical properties, further distinguishing these terms from the definition of an element.