Elements, Compounds, and Mixtures Now that we have learned about the development of the atom, the structure of the atom, and how elements are arranged on the periodic table. This chapter we are going to compare and contrast elements compounds, and mixtures. We are going to focus on the difference between pure substances and mixtures and what category does everything fall into.

Matter can be classified into elements compounds, and mixtures. Matter can be classified into elements, compounds, and mixtures. Tonight we will focus on the first type of particle…the element.

Elements, the Simplest Substances An element is defined as a pure substance that cannot be broken down into simpler substances by chemical or physical means. A pure substance is a substance that contains only one kind of particle. An element contains only one kind of particle (an atom).

Properties of Elements Each element can be identified by its unique properties. These properties are referred to as characteristic properties. (ex: magnetic, radioactivity, density, melting point, etc) Characteristic properties include BOTH physical and chemical properties.

Classifying Elements by Their Properties Elements are grouped into categories according to the properties that share. There are three major categories of elements. Metals-shiny, conducts heat and electricity, malleable, ductile (found on the left and in the center of the periodic table) Non-metals-dull, non-conductors, brittle (found on the right side of the periodic table) Metalloids-have properties of both metals and non-metals(located along the “staircase/zigzag between metal and non- metals.

SECTION 2: Compounds Because most elements easily change chemically, they are rarely found alone in nature.

Compounds: Made of Elements A compound is a pure substance that is made of 2 or more elements that have combined chemically. A particle of an element is an atom. A particle of a compound is a molecule. When elements join to form a compound, they do so in a specific ratio based on their masses (we are interested in the ratio of the number of atoms H2O is a ratio of 2 H to 1 O)

Properties of Compounds Compounds have physical and chemical properties. A compound’s properties are different than the properties of the elements that came together to make the compound.

Breaking Down Compounds Some compounds can be broken down by chemical changes into the elements that make them. Some compounds do not break down into their elements, but into other simpler compounds. Chemical changes are required to break down compounds. The addition of energy may be necessary to cause the chemical change. Energy can be added by applying heat or an electric charge.