Atoms are very small things. An atom is the smallest particle of matter that still retains the chemical properties of that type of matter. An atom of gold is the smallest piece of gold there can be and still behave like gold. If you cut an atom of gold, it will no longer be gold.
What are Atoms? How small are atoms? Atoms are measured on the scale of 10 -10 meters. Or 1 atom is approximately 0.0000000001 meters wide. Or in other words, in 1 meter, you can fit about 10,000,000,000 atoms side by side. There are 350,000 times more atoms in single cup of water than there are cups of water in the all of world’s oceans.
What is an Element? An element is a pure substance that cannot be broken down into simpler substances by any physical or chemical means. Atoms are the smallest possible pieces of elements that still behave like the element. e.g. same melting point, strength, etc. Each element has a unique type of atom. All atoms of carbon are pretty much the same as each other, but different than atoms of oxygen.
Combinations of Elements When elements are grouped together, they make the everyday substances that you and I are familiar with. Water, wood, humans, dirt, etc. Depending on how the elements are combined, the combinations are called either: compounds mixtures, or solutions You will learn more about this in Chemistry.
Brownian Motion Individual atoms are much much smaller than we can see, so how do we know they exist? In 1827, Robert Brown observed that particles of pollen floating in water moved in a “herky jerky” random path.
Brownian Motion It was as if the particles of pollen were being hit by many smaller particles. Later, Einstein concluded these particles were atoms. The random movement of particles because of their collisions with atoms is called Brownian Motion in Brown’s honor.