Atomic Theory Song

Matter & The Atomic Model A Timeline of Discovery

Matter The term matter describes all of the physical substances around us: your table, your body, a pencil, water, and so forth Defined as anything that has mass and takes up space (has volume) Includes all things that can be seen, tasted, smelled, or touched Does not include heat, sound, or light

Matter is made of atoms

The Atomic Model A Timeline of Discovery Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily In the case of atoms, scientists use large models to explain something that is very small Models of the atom were used to explain data or facts that were gathered experimentally. So, these models are also theories

Early Models of the Atom Democritus Greek Philosopher( 470-380B.C) Universe was made of empty space and tiny bits of stuff Called these tiny bits of small, hard particles he called “ atomos” Atoms could not be divided into smaller pieces

Early Models of the Atom Dalton 1808 Created the first Atomic Theory. He viewed atoms as tiny solid balls. His theory had 4 statements.

Dalton’s Theory All elements are composed of indivisible particles. Atoms of the same element are the same Atoms of different elements are different. Compounds consisted of atoms of different elements combined together

Early Models of the Atom JJ Thompson 1897 He was the first scientist to show that atoms were made of even smaller things.

Early Models of the Atom Thompson Plum pudding model Atom made of a positively charged material with the negatively charged electrons scattered through it.

JJ Thompson’s Ideas

Cathode Ray Tube Experiment

Early Models of the Atom Rutherford 1911 Discovered protons and nucleus

Early Models of the Atom Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside

Rutherford’s Gold Foil Experiment

Early Models of the Atom Bohr 1913 Electrons move in around the nucleus in specific layers or shells Every atom has a specific number of electron shells.

Early Models of the Atom Chadwick 1932 Discovered the neutron

Ernst Schrödinger 1887-1961 Werner Heisenberg 1901-1976 Quantum Mechanical Model 1926 Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed Electrons are particles and waves at the same time Developed quantum numbers based on theories of Einstein and Planck

Orbitals

Dmitri Mendeleev     In the late 1860s, Mendeleev began working on his great achievement: the periodic table of the elements. By arranging all of the 63 elements then known by their atomic weights, he managed to organize them into groups possessing similar properties. Where a gap existed in the table, he predicted a new element would one day be found and deduced its properties

Henry Moseley 1913 When atoms were arranged according to increasing atomic number, the few problems with Mendeleev's periodic table had disappeared. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements.