ELEMENTS AND COMPOUNDS

• Elements - simplest pure substance that make up all matter
• at present there are about 118 known elements that vary in abundance
• Compounds are classified as either organic or inorganic
• Organic compounds, also called carbon compounds, are substances that contain the element carbon.
• Metals - are dense, shiny, malleable (can be flattened into sheets), ductile (can be drawn intowires), and good conductors of heat and electricity.
• Nonmetals - are agroup of elements that are generally dull, brittle, and poor conductors of heat and electricity.
• Silicon Dioxide or Silica - the most abundant compound in the earth's crust It is also the building block of rocks and soil
• DMITRI MENDELEEV - In 1869, he created the frame work that became the modern periodic table, leaving gaps for elements that were yet to be discovered