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The Development of the Theory of the Atom THE INDIVISIBLE ATOM GREEK – DEMOCRITUS (450 BC) 1. Atom was _________________________ 2. Theorized the _______________________ of the atom 3. Also, theorized that there were just four 'elements' - _______, _______, _______, and _______. JOHN DALTON (1803) 1. Atom was _______________________ 2. All _____________________ are composed of atoms 3. The same atoms for one element are __________________________ alike 4. Atoms are neither created nor destroyed in a ________________________. 5. In a chemical reaction, atoms are ____________________________, _________________________, or _______________________________. THE DIVISIBLE ATOM J. J. THOMASON (1897) 1. discovered the _________________ using the cathode ray tube. 2. determined that the electron was smaller than a __________________ atom. 3. Knew the atom was _____________ and the electron was ___________________, so there must be positive material with a lot more mass. 4. Said the atom was a _______________________________ material throughout which _________________ charged electrons were scattered - Plum Pudding or Chocolate Chip Cookie Model. ERNEST RUTHERFORD (1909) 1. Did a famous gold foil experiment (the _____________ __________________ experiment) 2. Calculated that the atom was mostly ___________________ through which ________________ move. 3. Concluded that the atom has a __________, dense, _________________ charged, _________________-located nucleus surrounded by negatively charged _______________. ERNEST RUTHERFORD (1919) 1. Called the positive particles ____________________. ERNEST RUTHERFORD and JAMES CHADWICK (1932) 1. showed the nucleus also had ______________________ 2. The neutron was basically equal in mass to the proton but had _______ ____________________ charge. NEILS BOHR (1914) 1. Concluded that ________________ moved around the nucleus in definite orbits or ___________________________. DALTON REVISITED 1. Atom was indivisible. _____________ 2. All elements are composed of atoms. _____________ 3. The same atoms for one element are exactly alike. _____________ 4. Atoms are neither created or destroyed in a chemical reaction. _____________ 5. In a chemical reaction, atoms are separated, combined, or rearranged. _________ THE CURRENT ATOM is ___________________ shaped with a dense, centrally located, positive nucleus containing _____________ and __________________. surrounded by one or more negatively charged ________________ in an electron cloud. Most of the atom’s _______________ consists of fast moving electrons traveling through the _______________________ that surrounds the ________________. Electrons are held within the atom by an ______________________ to the positive nucleus. The nucleus has _____________ neutrons and _______________ protons and _____________ of the mass. Since atoms are electrically neutral, the ______________ of protons must ______________ the number of electrons. ATOMIC STRUCTURE ELEMENT: One of the __________ known _____________ substances. Listed on the periodic table. ATOM: ______________________ piece of matter that still retains the properties of that matter. ______________________ in the world is made of atoms. NUCLEUS: _________________ of the atom; _________________ of the mass of the atom; contains _______ particle types; has a _______________________ charge. ELECTRON CLOUD: Surrounds the _____________________; Contains _______ particle type; Has a ____________________ charge. 1. PROTON, p+: All are _____________________, regardless of the element. Location: ________________; Charge ______________________; Relative mass ______________ 2. NEUTRON, n: All are _____________________, regardless of the element. Location: ________________; Charge ______________________; Relative mass ______________ 3. ELECTRON, e-: Location: ________________; Charge ______________________; Relative mass ______________; Number in an atom: number of electrons = __________________ protons (neutral atom) What makes one element different from another element? ____________________________________ IMPORTANT NUMBERS ATOMIC NUMBER, Z: equals the number of ________________________________; determines the ____________________ of the element; On the periodic table, starts at __________ and goes up in order; It is the “5” in the symbol to the right. ATOMIC MASS: the ____________________ of the masses of the isotopes of an atom; the ______ on the periodic table; IT IS ________ the masses of the protons, neutrons, and electrons added together! MASS NUMBER, A: the number of __________________ and ___________________ (nucleons) added together; take the ______________________ (round!) of the atomic mass to get the mass number; It is the “11” in the symbol to the right; Also can be written after the element’s name: _________________________. HOW DO YOU DETERMINE THE NUMBER OF….. PROTON NEUTRON ELECTRON REMEMBER: The atomic number of an element _______________ changes. The number of protons is __________________ the same. The number of ______________________________________________ can change and the element is still the same element. =============================================================== PRACTICE: 1. How many protons and electrons are present in a vanadium atom? ________ 2. How many protons and electrons are present in a nitrogen atom? ________ 3. How many protons and electrons are present in an argon atom? ________ 4. What is the name of the element that has atoms that contain 5 protons? ____________ 5. How many protons, neutrons, and electrons are present in zirconium-91? protons _____ neutrons _____ electrons _____ 6. How many protons, neutrons, and electrons are present in cesium-140? protons _____ neutrons _____ electrons _____ 7. What is the atomic number and the mass number for the element with 27 protons and 32 neutrons? Atomic # ______ Mass # ______ 8. What is the atomic number and mass number for the element with 84 protons and 125 neutrons? Atomic # ______ Mass # ______