Chapter 7 Summary
• The theory that all matter is comprised of tiny pieces was first proposed by the ancient Greeks (Democritus). It was Democritus that first used the word “atom” (from the Greek “atomos” meaning “indivisible”).
• Atomic theory has undergone revisions as better experiments produced better insight. Principal among the scientists involved in studying the atom are:
o John Dalton who likened atoms to small spheres.
o JJ Thomson who discovered the electron and developed the “plum pudding” model of the atom.
o Ernest Rutherford who, with his Gold Foil Experiment, discovered that the atom is mostly empty space with a small, dense, positively-charged nucleus surrounded by orbiting electrons.
o Niels Bohr who put the electrons in specific energy levels.
• The three sub-atomic particles are Protons, Neutrons, and Electrons.
• Atoms are extremely small, mostly empty space, extremely old, and recycled.
• The electromagnetic force causes opposite charges to attract and like charges to repel. Therefore Protons are attracted to Electrons, Protons repel Protons, and Electrons repel Electrons.
• When Protons are made to come extremely close together, i.e. when they are moving very fast and under great pressure, they can fuse together and be held there by the Strong Nuclear Force.
• Isoptopes are atoms of the same element that have different atomic masses.
• Ions are atoms that have a net electrical charge. i.e. the number of electrons it has does not equal the number of protons.
• The Bohr Model of the atom depicts the electrons “seated” in their appropriate energy levels.
• Atomic theory has undergone revisions as better experiments produced better insight. Principal among the scientists involved in studying the atom are:
o John Dalton who likened atoms to small spheres.
o JJ Thomson who discovered the electron and developed the “plum pudding” model of the atom.
o Ernest Rutherford who, with his Gold Foil Experiment, discovered that the atom is mostly empty space with a small, dense, positively-charged nucleus surrounded by orbiting electrons.
o Niels Bohr who put the electrons in specific energy levels.
• The three sub-atomic particles are Protons, Neutrons, and Electrons.
• Atoms are extremely small, mostly empty space, extremely old, and recycled.
• The electromagnetic force causes opposite charges to attract and like charges to repel. Therefore Protons are attracted to Electrons, Protons repel Protons, and Electrons repel Electrons.
• When Protons are made to come extremely close together, i.e. when they are moving very fast and under great pressure, they can fuse together and be held there by the Strong Nuclear Force.
• Isoptopes are atoms of the same element that have different atomic masses.
• Ions are atoms that have a net electrical charge. i.e. the number of electrons it has does not equal the number of protons.
• The Bohr Model of the atom depicts the electrons “seated” in their appropriate energy levels.