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Elements

Elements. Patterns. The atomic number increases left to right and top to bottom? The atomic mass increases with the atomic number? Most names end in ium? Symbols ALWAYS start with a capital letter! Most names match the symbol. Elements. Weird Names!. Why Weird names?. Atomic Number.

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Elements

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  1. Elements

  2. Patterns • The atomic number increases left to right and top to bottom? • The atomic mass increases with the atomic number? • Most names end in ium? • Symbols ALWAYS start with a capital letter! • Most names match the symbol.

  3. Elements

  4. Weird Names!

  5. Why Weird names?

  6. Atomic Number • We could say the atomic number establishes the identity of the atom. • Each element has its own atomic number. • This number represents the number of protons in the element. • ATOMIC NUMBER = NUMBER OF PROTONS • Number of Protons determines the element.

  7. What element is this?Helium e- = 2 Electrons negatively charged. Electron Orbit. Nucleus P+ =2 N = 2 Protons Positively charged. Neutrons neutrally charged.

  8. Element Scavenger Hunt • What is the element with 8 protons, 8 electrons and 8 neutrons? • Oxygen. • What is the element with 5 protons, 5 electrons and 6 neutrons? • Boron. • What is the element with 1 proton, 1 electron and 0 neutrons? • Hydrogen.

  9. Important Notes • The identity of the element is based on the Protons, ONLY! • The electrons happen to equal protons now but that WILL change. • Do the neutrons always equal protons? • No, sometimes same, more, less. • Sometimes ZERO!

  10. Finding Number of Neutrons • Mass is the amount of matter in an object. • What makes up an atom? • Protons, neutrons and electrons. • So atomic mass can be found by looking at the parts that make up the atom. • We call the one unit of measure at the atomic level an Atomic Mass Unit (AMU) • Atomic Mass = # P + # N + #e

  11. Let us Try • Helium has 2 protons, 2 neutrons and 2 electrons so it’s atomic mass must be 6…? • NO it is 4.003 • WHY? • Experiments have shown that the masses of protons and neutrons are approximately the same. • One of these particles has the mass of about 1,840 electrons. • Since the mass of the electron is so small in comparison we consider them to be 'massless'. • So Protons and Neutrons have 1 AMU and electrons have zero.

  12. Determining Neutrons • ATOMIC MASS = # of PROTONS + # of NEUTRONS • A M - # P = # N • How many neutrons in sodium? • A M - # P = # N • 22.93 – 11 = # N • 11.93 = # N ???? • How can you have part of a Neutron? • You cannot! • We must round the Atomic Mass before we calculate. 22.93 = 23 – 11 = 12 Neutrons.

  13. You Try • Take elements 19 to 36 • Draw the Bohr model for each. • Make sure you have the right number of Protons, electrons and Neutrons.

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