Elements: • A pure substance containing only one kind of atom . • An element cannot be separated into simpler materials (except during nuclear. reactions).

Atoms are the building blocks of all matter. When a substance contains only one type of atom, it is called an element. An element is a pure substance and is made of only one type of atom; it cannot be broken down into a simpler substance.

Some elements are monatomic, meaning they are made of a single (mon-) atom (-atomic) in their molecular form. Helium (He, see Fig. 2.8) is an example of a monatomic element.

A chemical element is a pure substance that consists of one type of atom. Each atom has an atomic number, which represents the number of protons that are in the nucleus of a single atom of that element.

The two main types of pure substances are compounds and elements. They consist of a single type of particle or compound.

Types of Mixtures There are two main categories of mixtures: homogeneous mixtures and heterogeneous mixtures.

Examples of Pure Substances All elements are mostly pure substances. A few of them include gold, copper, oxygen, chlorine, diamond, etc. Compounds such as water, salt or crystals, baking soda amongst others are also grouped as pure substances.

Types of Substances Pure Substance: The substances that are free from any kind of mixture and contain only one kind of particle are pure substances. Examples of pure substances include iron, aluminum, silver, and gold. Mixtures: Substances that have two or more different particles are mixtures.

A pure chemical compound is a chemical substance that is composed of a particular set of molecules or ions that are chemically bonded. Two or more elements combined into one substance through a chemical reaction, such as water, form a chemical compound.

Different substances have different properties; density is one property that can be used to tell two substances apart. Density is a property that does not depend on the shape or size of an object.

Chemists and nuclear scientists have different definitions of a pure element. In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons. Nuclear scientists, however, define a pure element as one that consists of only one stable isotope.

Hydrogen is the most abundant element in the universe.

Pure Element Examples

• Hydrogen (H) – nonmetal.
• Helium (He) – nonmetal.
• Oxygen (O) – nonmetal.
• Neon (Ne) – nonmetal.
• Nitrogen (N) – nonmetal.
• Carbon (C) – reactive nonmetal.
• Silicon (Si) – metalloid.
• Magnesium (Mg) – alkaline earth metal.

Examples of elements include iron, oxygen, hydrogen, gold, and helium. An important number in an element is the atomic number. This is the number of protons in each atom.

What are 5 pure elements that can be found in your home?

• Argon and tungsten are in incandescent light bulbs.
• Mercury is in some thermostats and in switches in space heaters that turn off when tipped over.
• Copper is used in electrical wiring and in some water pipes.
• Carbon is in pencils.
• Phosphorous is on the tips of matches and ignites from the friction of striking them.

Examples of pure substances include tin, sulfur, diamond, water, pure sugar (sucrose), table salt (sodium chloride) and baking soda (sodium bicarbonate). Crystals, in general, are pure substances. Tin, sulfur, and diamond are examples of pure substances that are chemical elements.

A pure substance is a type of matter which exists in its most basic or purest form and cannot be broken down further. Examples of pure substances include water, gases like carbon dioxide, oxygen and metals like platinum, gold and silver.

Here are a few more examples:

• Smoke and fog (Smog)
• Dirt and water (Mud)
• Sand, water and gravel (Cement)
• Water and salt (Sea water)
• Potassium nitrate, sulfur, and carbon (Gunpowder)
• Oxygen and water (Sea foam)
• Petroleum, hydrocarbons, and fuel additives (Gasoline)

A pure substance has a definite and constant composition — like salt or sugar. A pure substance can be either an element or a compound, but the composition of a pure substance doesn’t vary.

Crystal methamphetamine (‘ice’, ice drug) is a stimulant drug, which means it speeds up the messages travelling between the brain and the body.

Main compounds of milk are lactose and casein. And it is also called a colloidal mixture (i.e. in which one substance of microscopically dispersed insoluble or soluble particles is suspended throughout another substance). Therefore milk is regarded as a mixture not as a pure substance.