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are made up of subatomic particles called protons, neutrons, and electrons. 

The ____ of an atom is made up of protons and neutrons. 

The ______ orbit the nucleus in an electron cloud. 

______ are the basic building blocks of chemical elements. 

The nucleus of an atom is made up of _____

have a positive charge, while electrons have a negative charge. 

there were only four elements: fire, air, water, and earth that make up matter.

proposed the law of definite proportions.

A given compound always contains the same elements in the same proportion by mass, regardless of its source or how it was formed.

supported this idea and added a fifth element which he called aether or ether.