the simplest type of matter with unique physical and chemical properties. It consists of only one kind of atom and, therefore, cannot be broken down into a simpler type of matter by any physical or chemical methods. Each element has a name, such as silicon, oxygen, or copper. A sample of silicon contains only silicon atoms. The macroscopic properties of a piece of silicon, such as color, density, and combustibility, are different from those of a piece of copper because the submicroscopic properties of silicon atoms are different from those of copper atoms; that is, each element is unique because the properties of its atoms are unique. Can you name some of the elements that you are familiar with? How are they used by human? Here are some example elements and particle illustrations of elements. krypton neon carbon Figure 2. Sample elements hellum lodine Figure 3. Particle model pictures of elements There are 118 different elements. Each element has different set of properties. No two elements have the same set of properties. In the case of hydrogen and oxygen, even though they are both in gaseous state at room temperature, they behave differently when exposed to a flame or spark of flame. Hydrogen gives off a "pop" sound when ignited, while oxygen induces a brighter spark. This difference in behavior implies a difference in property. In effect, hydrogen and oxygen are different substances, or to be more specific, they are different elements. 118 is quite a big number! Thanks to the works of our early scientists, they were able to systematically organize all the 118 elements in what we call the Periodic Table of Elements. Amazingly, they were able to logically arrange the elements in the table enabling one to have an idea of the properties of several elements by knowing other elements related to them. This means that there is no need to memorize the periodic table, but it is an advantage to be familiar with it. Among these 118 elements in the periodic table; 94 of them are found in nature, while the others are made by humans. Every element is unique. Most of the elements are solids, like the metals. At room temperature, 11 elements are gases, while bromine and mercury are the only two liquids.
