Q1_05_Atomic Structures (subatomic particles).pdf

Republic of the Philippines DEPARTMENT OF SCIENCE AND TECHNOLOGY PHILIPPINE SCIENCE HIGH SCHOOL - CALABARZON REGION CAMPUS Sub-atomic Particles Quarter 1 Week 2b CHEMISTRY 1 – GENERAL INORGANIC CHEMISTRY Vincent Guiller G. Amores Special Science Teacher I Chemistry Unit...

Republic of the Philippines DEPARTMENT OF SCIENCE AND TECHNOLOGY PHILIPPINE SCIENCE HIGH SCHOOL - CALABARZON REGION CAMPUS Sub-atomic Particles Quarter 1 Week 2b CHEMISTRY 1 – GENERAL INORGANIC CHEMISTRY Vincent Guiller G. Amores Special Science Teacher I Chemistry Unit – CID [email protected]  1. Discovery of Electrons J.J. Thomson’s Cathode Ray Tube Experiment 2  Joseph John Thomson ▷ demonstrated that cathode rays could be deflected, or bent, by magnetic or electric fields, which indicated that cathode rays consist of charged particles (1897) ▷ able to calculate the mass-to-charge ratio of the particles ▷ able to conclude that the particles had a net negative charge ▷ adapted the word “electron” to refer to these particles 3  Robert Millikan experimented ▷ experimented using electrically charged oil droplets, which allowed him to calculate the charge on a single electron (1906 – 1914) ▷ able to calculate the mass of an electron with Thomson’s mass-to-charge ratio 𝑚𝑎𝑠𝑠 ▷ × 𝑐ℎ𝑎𝑟𝑔𝑒 = 𝑚𝑎𝑠𝑠 𝑐ℎ𝑎𝑟𝑔𝑒 4 J.J. Thomson’s Plum-Pudding Model (1904) Positive matrix ▷ atoms were imagined as spherical structures made up of a positively charged matrix ▷ matrix represented the bulk of the atom's mass ▷ matrix is solid structure analogous to the "pudding" in a plum pudding dessert 5 J.J. Thomson’s Plum-Pudding Model (1904) Electrons Embedded ▷ within this positively charged matrix, negatively charged electrons were embedded like "plums" in a pudding ▷ electrons were thought to be distributed uniformly throughout the atom 6 J.J. Thomson’s Plum-Pudding Model (1904) Neutral Overall ▷ atom as a whole was electrically neutral ▷ positive charge of the matrix balanced out the negative charge of the embedded electrons 7 J.J. Thomson’s Plum-Pudding Model (1904) Fundamental Particles ▷ electron was a fundamental particle and could not be divided into smaller parts 8  2. Radiation 9 Historical Milestones ▷ Becquerel discovered that certain minerals, such as uranium salts, emitted a new form of energy. ▷ Marie and Pierre Curie coined the term radioactivity to describe the emission of energy rays by matter. ▷ Rutherford showed that compounds of uranium and other elements emitted at least two distinct types of radiation 10  3. Discovery of Protons (Nucleus) Rutherford’s Gold Foil Experiment 11  Ernest Rutherford ▷ demonstrated that Thomson’s model of the atom was incorrect using the gold foil experiment 12 Rutherford’s Nuclear Model (1911) Central Nucleus ▷ introduction of a small, dense, and positively charged central nucleus at the center of the atom. ▷ nucleus contained most of the atom's mass and was responsible for the positive charge of the atom 13 Rutherford’s Nuclear Model (1911) Electrons in Orbit ▷ electrons orbited the nucleus in fixed, discrete energy levels or electron shells ▷ electrons move in circular or elliptical paths similar to planets orbiting the sun 14 Rutherford’s Nuclear Model (1911) Mostly Empty Space ▷ One of the significant implications of Rutherford's model was the idea that most of the atom was empty space ▷ electrons, being much lighter than the nucleus, occupied this space around the nucleus 15 Rutherford’s Nuclear Model (1911) Neutral Atom ▷ the atom as a whole was electrically neutral ▷ positive charge of the nucleus was balanced by the negative charge of the orbiting electrons 16  4. Discovery of Neutrons Chadwick’s Beryllium-Paraffin Experiment 17  James Chadwick ▷ conducted experiments using beryllium as the target material. When bombarded with alpha particles, beryllium emitted an unknown type of radiation that was not deflected by electric or magnetic fields ▷ concluded that this radiation consisted of electrically neutral particles with a mass slightly greater than that of protons. These neutral particles were identified as neutrons. ▷ Neutrons have no electrical charge, which is why they were not deflected by electric or magnetic fields. 18 Summary 19 For consultations: Email address: [email protected] Phone number: 0960 200 8383 Office: Ground Floor, ASTB Please inform me at least a day prior to check availability. 20