this was invented by mendeleev, a russian, 120 years ago. it's called the periodic table, and it's worth more to chemists than all of the pieces of equipment in our laboratories. what are the properties of the substances in the world around us? there are two types of propertis. chemical properties refer to the element's ability to combine with other elements and form compounds. physical properties include density, hardness, melting point, boiling point, and conductivity. each element is different from every other eleme in its chemical and physical properties. this uniqueness can be traced to the element's atomic structure, but some groups of elements also share common properties that vary systematically and predictably. these common properties are the basis of the modern periodic table. there are 109 elements in it. 88 occur naturally. the other 21 are manmade, or artificial, elements. for centuries, latin was the common language of science, so many elements have latin names. for instance, iron was ferrum, so its abbreviation became fe. gold