ATOM
Ernest Rutherford's Atomic Theory (1910's) - Rutherford proposed a Gold Foil Experiment as he was not convinced of Thomson's atomic model. He then accidentally discovered a nucleus due to the positively charged alpha particles that failed to pass through the gold foil.
John Dalton's Atomic Theory (1800's) - Dalton adapted Democritus' atomic theory and developed a new atomic theory with his experiments and supported observations that eventually led to the acceptance of the idea of atoms.
Neil Bohr's Atomic Theory (1910's) - Bohr improved Rutherford's model and developed a new one similar to the solar system and discovered that electrons move in definite orbits around the nucleus.
JJ Thomson's Atomic Theory (1890's) - Thomson discovered electrons through his experiment with cathode-ray tube that led to the idea that atoms are not the smallest, but rather, we're made up of much smaller things—positively charged matter and negatively charged electrons existing inside of it.
Aristotle (300 BC) - Theorized that all matter was made of the element fire, air, water, and earth; and have a property of hot, cold, dry, and wet.
Democritus' Atomic Theory (400 BC) - The first philosopher to come up with the idea of the atom. He postulated that all matter was composed of tiny, indivisible, and indestructible units wherein he called these units atoms a Greek word for indivisible.
Erwin Schrödinger’s Atomic Theory (1920's) - Schrödiger's Wave Theory is the latest atomic theory wherein it was found out that electrons do not orbit in the planet-like orbits but rather in a so-called electron cloud around the nucleus.
James Chadwick's Atomic Theory (1930's) - Chadwick discovered that atoms consisted not only of protons and electrons but also neutrons—neutrally charged subatomic particles with the same mass as protons that occupy the nucleus of the atom.
Democritus' Atom -
Democritus' Atom
a round sphere with no electrons, protons, and neutrons;
separated from one another by empty space;
Atoms of different substances differ in size, weight, and shape.
Dalton's Billiard Ball Model
atoms are tiny and indivisible;
atoms of one element are all the same;
atoms of different elements are different;
compounds form by combining atoms;
a chemical reaction is a rearrangement of atoms.
Thomson's Plum Pudding Model
presence of positively charged matter with negatively charged electrons;
all atoms are neutrally charged.
Rutherford's Nuclear Model of Atom
atom is mostly open space with the presence of nucleus in the middle;
electrons orbiting onto nucleus;
the nucleus is a dense mass of positively charged par
Bohr's Planetary Model of Atom
electrons orbit only in a certain orbits called "stationary" orbits around the nucleus;
the energy of the orbit is related to its size;
radiation is when an electron moves from one level to another.
Chadwick's Neutron Model
existence of neutron
an atom was now a nucleus containing positively charged protons and neutral neutrons with
the rest of the atom being space in which negatively charged electrons.
Schrödinger's Quantum Mechanical Model
does not define the exact path of an electron; nucleus surrounded by an electron cloud
the location of the electron can only be given as a probability that the electron is somewhere in a certain area.
STRUCTURE OF ATOM
ELECTRON - An electron is a subatomic particle that is negatively charged. It can be either free (not linked to any atom) or tied to an atom's nucleus. Electrons in atoms reside in spherical shells of varying radii, which indicate different energy levels. The more the energy contained in the electron, the bigger the spherical shell.
PROTON - A proton is one of the three major particles that comprise an atom. Protons are present in the atom's nucleus. This is a small, dense area in the atom's core. Protons have a positive electrical charge of one (+1) and a mass of one atomic mass unit (amu), or approximately 1.67 10-27 kg.
NEUTRON - an uncharged fundamental particle with a mass almost equivalent to the proton and found in all known atomic nuclei except the hydrogen nucleus.