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Elements and Compounds. 3 KINDS OF MATTER. Elements Compounds Mixtures. Elements. All (living and nonliving) of the different kinds of matter in the universe is made from about 100 different substances, called elements.
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3 KINDS OF MATTER • Elements • Compounds • Mixtures
Elements • All (living and nonliving) of the different kinds of matter in the universe is made from about 100 different substances, called elements. • Elements are called the building blocks of matter because all matter is composed of elements. • Each element is made up of the same type of atoms.
The Periodic Table • The periodic table organizes the elements in a particular way. A great deal of information about an element can be gathered from its position in the period table. • For example, you can predict with reasonably good accuracy the physical and chemical properties of the element. You can also predict what other elements a particular element will react with chemically. • Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements.
Compounds • A compound is a substance made of two or more different kinds of elements chemically combined in a specific ratio. • Each compound is represented by a formula that uses symbols to identify which elements are present. • A formula shows the ratio of elements in the compound. • H2O – ratio of Hydrogen is 2:1 Oxygen
Formulas • The symbols make up the formula. A formula is just chemical shorthand for the compound. • The subscript lets us know how many atoms are present.
Molecules • A molecule is formed when two or more atoms join together chemically. • Diatomic molecules are made of two atoms of the same element. • Hydrogen – H2 • Oxygen – O2
What is the difference between a compound and a molecule? • A molecule is formed when two or more atoms join together chemically. • A compound is a molecule that contains at least two different elements. • All compounds are molecules but not all molecules are compounds.
Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. • Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element.
Molecule • The smallest bit of each of these substances would be referred to as a molecule. For example, a single molecule of molecular hydrogen is made from two atoms of hydrogen. • A single molecule of water is made from two atoms of hydrogen and one atom of oxygen.
Compound • A compound has properties different than the elements that make it up. • The parts of a compound are present in specific ratio’s.
Water is H2O • An oxygenatom can bond with two hydrogen atoms to make a molecule we call water. Water is an example of a compound, because it contains more than one kind of atom. The formula for water is H2O, meaning there are two hydrogen atoms for each oxygen atom.
Carbon Dioxide CO2 • Carbon dioxide molecules are made from one carbon and two oxygen atoms joined together by covalent bonds. The chemical symbol is CO2.
Molecule • When a compound is broken down into its’ smallest piece it is called a molecule. You should be able to write the formula for the following: • Water • Oxygen • Carbon Dioxide
