Name:_________________________________ Read, highlight, and answer questions on Schoology! Elements, Compounds, and Minerals...Oh My! There are around four thousand different minerals in the world. They are all naturally occurring inorganic solids. Each mineral is defined by its particular chemical composition and crystal structure. To explain what a mineral is properly, we have to introduce you to a bit of chemistry. Minerals are made up of chemical elements. A chemical element is a substance that is made up of only one kind of atom. Have you heard of oxygen, hydrogen, iron, aluminium, gold and copper? These are all chemical elements. But what is an atom? An atom is the smallest unit of any chemical element. They are the building blocks that make up each chemical element, and are far too small to see with the naked eye. Imagine a small piece of copper, for example. Even the tiniest piece of copper is made up of billions and billions of copper atoms. There are 103 types of atoms, and because each chemical element is made up of only one kind of atom there are 103 chemical elements. Billions and billions of copper atoms stack together to form a piece of copper. Each mineral has a fixed chemical composition. Some minerals are made up of just one chemical element ­ they contain only one type of atom. Native copper is made up of copper atoms only. Most minerals are chemical compounds ­ they contain atoms of more than one chemical element So what is a chemical compound? Put it this way. Just as chemical elements are made up of atoms, a chemical compound is made up of molecules. Each molecule in a chemical compound is made up of two or more different atoms connected together. Halite is a chemical compound. It is also called sodium chloride, but you would probably know halite better as rock salt ­ yes, the kind you put on your fish and chips. Each molecule of halite contains one atom of an element called sodium connected to one atom of an element called chlorine. Halite always contains just as many sodium atoms as it does chlorine atoms: this 'formula' does not vary ­ halite, like all other minerals has a definite chemical composition. Chlorine and sodium atoms will connect together to make halite molecules. The atoms in a mineral are arranged in an organised 'atomic structure'. They connect together to form molecules, and the molecules stack together in a regular pattern to form a crystal. The shape of a crystal depends on the way the molecules are stacked up inside it. There is a set way in which the sodium atoms "connect" to the chlorine atoms to make a halite molecule, and these molecules can stack together to form a halite crystal. Halite molecules stack together to form halite crystals ­ this is the salt we eat everyday. All the properties of a mineral ­ its crystal shape, hardness, colour, lustre ­ depend on which chemical elements it is made of and how the atoms of these elements are arranged inside it. THE EARTH'S CRUST The whole earth is made of rocks and minerals. Inside the earth there is a liquid core of molten rock and on the outside there is a hard crust. If you compare the earth to an apple, the skin on the apple is like the crust on the earth. It is not very thick, but to us it’s big. You would have to dig upwards of 35 km (21 miles) to reach the next layer of Earth. The Crust makes up less than 1% of the total mass of the Earth. It is made minerals, but we know them as elements. The 8 elements that make up the Earth’s crust are… 46.6% Oxygen (O) 27.7% Silicon (Si) 8.1% Aluminum (Al) 5.0% Iron (Fe) 3.6% Calcium (Ca) 2.8% Sodium (Na) 2.6% Potassium (K) 2.1% Magnesium (Mg) The Mantle is the solid casing of the Earth and it makes up about 69% of the Earth’s mass. It is also made up of minerals like silicon, oxygen, aluminum and iron. The Core is mainly made of two main minerals iron and nickel. The core only makes up about 30% of the Earth’s mass. What Are Rocks, Minerals, And Elements? It is best if we clearly define what we are talking about when we discuss rocks, minerals and elements. Elements: Elements are atoms, the smallest piece that we can split matter into (except for subatomic particles and other things that we'll leave to the physicists). Different elements have different properties. Take two different elements: iron and helium. Iron is very different than helium. You wouldn't fill a balloon with iron any more than you would try to build a bridge out of helium. Minerals: Elements often are stacked together with other elements to form minerals. Minerals are simply a collection of one or more elements that are stacked neatly together in a form called a crystal structure. Rocks: Rocks are a composed of one or more minerals. A rock can be made up of only one mineral or, as shown in the figure, a rock can be made up of a number of different minerals. So, rocks are composed of one or more minerals and minerals are composed of one or more elements. How Do We Categorize Minerals? There are thousands of different kinds of minerals. Fortunately, they have systematic properties that allow geologists to organize them in a manner that makes it easier to understand their variety. Minerals belong to one of a variety of classes. These classes are based on the elements and crystal structure of a mineral. Some common mineral classes include: ● Silicates­ ​
Silicates have a silicon atom surrounded by four oxygen atoms. Quartz (silicon dioxide, SiO2) is a common silicate. ● Carbonates­ ​
Carbonates have a carbon atom surrounded by three oxygen atoms. Calcite (calcium carbonate, CaCO3) is a common carbonate found in limestones. ● Sulfates­ ​
Sulfates have a sulfur atom surrounded by four oxygen atoms. Gypsum (calcium sulfate, CaSO4 2H2O) is a common sulfate. ● Oxides­ ​
Oxides contain oxygen often combined with only one other (usually metal) element. Hematite (iron oxide, Fe3O4) is an example of an oxide. ● Halides­ ​
Halides are salts (sodium chloride, NaCl, or table salt being one particular kind of salt). All minerals within a mineral class are similar, but they also have important differences. For example, calcite (calcium carbonate), rhodochrosite (manganese carbonate), and siderite (iron carbonate) are all different kinds of carbonates. They all have the same carbon atom surrounded by three oxygen atoms, but they also have different atoms, such as manganese, iron, or calcium.