Download "stuff" that takes up space- is made of tiny particles called atoms

~ 7th Grade Science ~ Atoms & Elements Notes ~
* All matter- "stuff" that takes up space- is made of tiny particles called
atoms.
* The word "atom" comes from Greek; it means "indivisible."
* In the late 19th century (1800's), scientists discovered that atoms are
made of even smaller particles.
* Atoms are tiny. About one million (1,000,000) atoms would fit across the
thickness of a human hair.
* Atoms are made of subatomic particles: protons, neutrons, and electrons.
* Protons are massive (1 amu) and have a positive + charge. Neutrons are
massive (1 amu) and have a neutral charge (neither positive nor negative).
Electrons are extremely tiny (1/1,837 amu).
* Electrons orbit the nucleus of the atom, which is made of protons and
neutrons, in an "electron cloud," help in orbit by electromagnetic force—
opposites attract!
* An atom is defined by its atomic number: its number of protons. All
atoms of the same type- the same atomic number- belong to the same
element: for example, all atoms with 1 proton are hydrogen atoms, all
atoms with 8 protons are oxygen atoms.
* Each element has "characteristic intrinsic properties;" qualities shared by
every atom of the element.