Quarter 2 Bellwork 10/16/19 Answers must be complete! If you are missing a bellwork assignment, you may NOT copy it from your classmate. If you are absent, write absent for the day you were out Everything must be dated and numbered or your bellwork assignment will not be graded Bellwork should be started as soon as you get into class 1.Because we will be studying the unit of Atoms and the Periodic Table, why do you think the Periodic Table was invented? 2.What can we find on the Periodic Table? 3.What is the Periodic Table used for? Bellwork 10/17/19 1. Who were the 7 main people who contributed to the discovery of the atom? Atoms and the Periodic Table ATOMIC THEORY Democritus (400BC) Proposed that matter was formed of small pieces that could not be cut into smaller parts called atomos. In modern terms, an atom is the smallest particle of an element John Dalton (1803) Conducted many experiments centered on atoms and inferred that all atoms had certain characteristics: 1. Elements consists of atoms that can’t be divided 2. Atoms of the same element are alike and have the same mass 3. Atoms of an element can’t be changed into a different element 4. Compounds are formed by combining more than one element JJ Thomson (1897) Discovered that atoms contain negatively charged particles called an electron, but also proposed that atoms contain some sort of positive charge Ernest Rutherford (1911) Conducted Gold Foil Experiment which concluded that the atom is mostly empty space but has a dense, positive charge at its center called the nucleus He called a positively-charged particle in the nucleus, a proton Niels Bohr (1913) Suggested that electrons move only in specific orbits with fixed energies around an atom’s nucleus Erwin Shrodinger (1924) Developed the electron cloud model in which there is a cloud-like region where electrons can be found James Chadwick (1932) Discovered the existence of neutrons, which are particles with no charge
