Ch 2.3 Elements & Compounds
Objectives
• Explain the difference between an element and a compound.
• Identify the chemical symbols of elements, and name elements.
• Do you see Chemistry in this picture? Most people say no, they don’t. “Chemistry” can’t be “seen.”
• Therefore, Scientists represent atoms by using different colored circles, called a model.
• Models are tools that scientists use.
• Matter is composed of tiny particles called atoms.
• Not all atoms are alike, all matter is composed of about 100 different types of atoms.
• We call these 100 types of atoms the elements of the universe.
• Substances which cannot be broken down into simpler substances by chemical reactions are called elements.
• Each element is unique. Elements have their own physical and chemical characteristics.
• Below is an example of each element in “model format.” An element in model form is a single, colored circle.
• A model is a visual of experimental data. Chemists use models to represent matter, such as elements
• Elements are organized in a table called the periodic table of the elements
• This will be the most important tool that you will use in this class
• An element is identified by its symbol; this consists of one or two letters, usually derived from its name:
C = Carbon
Co = Cobalt
• Sometimes the element symbol does not match the element name. This occurs because the Latin name is sometimes used, i.e.
Cu = Copper (Cuprum)
• Each element is different from other elements because it has a different number of protons.
• As a result each element has unique physical & chemical properties.
• Elements are organized in the periodic table by the “Blue Number” called the atomic number.
• The atomic number is the number of protons in the element.
• Question#1 Answer: What is the atomic number of the element phosphorus?
A) P = 15 C) K
B) Po D) Kr
Ch 2.1 Elements Are Pure Substances
Objectives:
• Categorize a sample of matter as a substance or a mixture.
• Pure substances have fixed properties: – Fe is a metal and
magnetic
– S is a nonmetal and not magnetic
• Elements are pure substances.
Elements At The Atomic Level
• Pure substances have a fixed constant composition.
• Elements are all the same,
thus a pure substance.
http://www.privatehand.com/flash/elements.html The Element Song