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Matter and The Atom Dalton’s Atomic Theory States: 1. All _____________________is made up of small particles called ____________________ 2. Atoms cannot be ____________________________________into smaller particles. (they are recycled) 3. All atoms of the ___________element are identical in ___________and __________, but are different in mass and size from the atoms of_____________ element. a. Atoms of one element are the same-­‐ but are very different from all other elements, giving them their unique properties. 4. ________________are created when atoms of different elements link together in definite proportions. Example: An Oxygen Atom-­‐ has 8 electrons and protons A Hydrogen Atom-­‐ has 2 electrons and protons Explaining The Atom All atoms consist of subatomic particles: Protons:_______________________________________________ Neutrons: _____________________________________________ Electron: ______________________________________________ ! Complete the chart Charge Proton Location Relative mass 1 Electron Symbol Neutron 1 1/200 Atomic Number: _______________________________________________________________________ ! The_____________________ of protons is what makes each atom ________________________ ! Chemist have found that when elements are arranged by________________________________ (as seen with the periodic table), the elements that fall into the __________________________ ______________________________________________________________________________ 3 Li 6.94 12 Mg 24.31 Element Name:________________________ Atomic #:________ #of Protons:_________ Location of protons:____________________ Element Name:________________________ Atomic #:________ #of Protons:_________ Location of protons:____________________ Can you name the element with only one proton in its nucleus?________________________________ Atomic Mass: •
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_____________________________________________________________________________ ! You can find the atomic mass of each element on your periodic table? 3 Li 6.94 The atomic mass of lithium is:______________________ Now round the atomic mass:_______________________ Which element has an atomic mass of 9?________________________40?________________________ How do you determine the number of neutrons? ! Let’s try: Element Sodium (Na) Boron (B) Chlorine (Cl) Calcium (Ca) Atomic # Atomic Mass (rounded) # of Electrons (same as atomic #) # of Protons (same as # of electrons) 11 # of Neutrons 11 23 (22.99) 11 23-­‐11= 12 Check your understanding: 1. Do all atoms of the same element contain the same number of protons? Explain. 2. What is the maximum number of electrons that each of the first three electron orbits can hold? 3. Which of the following statements are correct? Re-­‐write the incorrect statements. a. The atomic number always equals the number of protons. b. The atomic mass can be smaller than the atomic number. c. The number of protons is always equal to the number of neutrons in an atom. d. The number of protons is always equal to the number of electrons in an atom. e. The protons and electrons are found in the nucleus of an atom Bohr-­‐ Rutherford Diagrams of an Atom A picture is worth a thousand words! When it comes to Bohr diagrams this holds true for atoms as well. A Bohr-­‐Rutherford diagram can be completed in a few simple steps, and when done properly shows the numbers and locations of protons, neutrons, and electrons of an atom. In order to input the correct numbers, we need to keep in mind: ! Atomic number = # of ___________________= # of ___________________in a neutral atom ! Atomic mass = mass number ! # neutrons = ______________________(rounded) -­‐ # ________________ Steps to completing a Bohr Diagram: 1. Record the # of protons and the # of neutrons in the nucleus 2. Start filling the electrons in the lowest energy level (closest to the nucleus) a. 1st energy level= holds _______electrons b. 2nd energy level= holds (up to) _______ electrons c. 3rd energy level= holds (up to) ______electrons 3. Fill in the electrons one energy level at a time, moving on only when the lower level is full! *HINT: use the sign of the cross m ethod for placing the electrons! How many electrons in the example above?____________________ How many energy levels are being used?______________________ How many electrons on the valance shell?_______ Is it full?_________________________________ What element is represented in this Bohr diagram?________________________________________ Patterns in the Periodic Table Did you notice any pattern emerging from the periodic table of Bohr-­‐Rutherford diagrams? How many orbits does the Bohr-­‐Rutherford diagram have in the elements of the alkaline earth metal family? Be-­‐ Mg-­‐ ! All atoms of the same family have the same number of electrons in their outermost (valence) shell. How many valance electrons are found on the Bohr-­‐Rutherford diagrams of the alkali metals family? Li-­‐ Na-­‐ K-­‐ ! This electron arrangement explains why the reaction alkali metal with water becomes more vigorous as you go down the group. ! The electron farthest from the nucleus has the weakest attraction so the valence electron is most likely the one to be lost.