Final answer:
An element is a fundamental chemical substance that cannot be broken down by ordinary chemical means. There are 118 known elements, each with a unique set of properties and a specified number of protons in their atoms. Pure elements can be identified by their distinct melting or boiling points and by chromatography tests.
Step-by-step explanation:
An element is a substance that cannot be broken down into simpler chemical substances by ordinary chemical means. Each element is composed of atoms with a fixed number of protons and exhibits unique properties. There are currently 118 recognized elements, some of which are stable while others are radioactive. Elements like iron, silver, gold, and copper are examples of these fundamental substances that make up all matter.
Elements stand in contrast to compounds, which are pure substances that can be broken down into simpler substances because they consist of more than one element chemically bonded together. While compounds have the capacity to be broken into their elemental components through chemical reactions, elements represent the simplest form of chemical substances and do not have this capability.
To determine if a substance is a pure element, techniques such as melting and boiling point analysis or chromatography can be utilized. Pure elements will exhibit a sharply defined melting or boiling point and will yield a single substance at the end of a chromatographic process, whereas impure substances will demonstrate a range of melting or boiling points and multiple components in chromatography.