Atoms and Elements What is an atom?Atoms are the basic building blocks of ordinary matter. Atoms can join together to form molecules, which in turn form most of the objects around you.Atoms are composed of particles called protons, electrons and neutrons. What is an element?An element is a substance that is made entirely from one type of atom. If you change the number of protons an atom has, you change the type of element it is.
Metals Metals Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most metals are malleable and ductile and are generaly denser than the other elemental substances.
Non-metals Non-metals A non-metal is an element on the periodic table that does not have the properties of a metal element. Non metals are usually found as gases.
The periodic table What is the periodic table? The periodic table arranges all the known elements in an informative array. Order generally coincides with increasing atomic mass.
compounds A chemical compound is a substance composed of two or more different elements chemically bonded together in a fixed proportion by mass.
Chemical reactions A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.
A common physical change occurs when matter changes from one phase to another. When an ice cube melts for example, it becomes liquid water. Physical reactions