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Atomic Structure

Atomic Structure. ELEMENTS. 115+ known elements 90 naturally occurring elements 14 most common elements: hydrogen ( H ) carbon ( C ) nitrogen ( N ) oxygen ( O ) sodium (Na) magnesium (Mg) aluminum (Al) silicon (Si) phosphorous ( P ) sulfur ( S ) chlorine (Cl) potassium (K)

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Atomic Structure

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  1. Atomic Structure

  2. ELEMENTS • 115+ known elements • 90 naturally occurring elements • 14 most common elements: • hydrogen (H) carbon (C) • nitrogen (N) oxygen (O) • sodium (Na) magnesium (Mg) • aluminum (Al) silicon (Si) • phosphorous (P) sulfur (S) • chlorine (Cl) potassium (K) • calcium (Ca) iron (Fe) • CHONPS = elements important for life

  3. ELEMENTS • all atoms of a specific element have the same number of protons • atoms of different elements have a different number of protons • arranged on Periodic Table to show trends

  4. PERIODIC TABLE

  5. ATOMIC SIZE

  6. SIZE • 1 mL H2O = • 100,000,000,000,000,000,000,000 atoms • 1023 atoms • …this is more than the number of drops of water in all lakes, rivers, and streams on Earth • Special microscopes for studying atoms: • transmission electron microscope • scanning tunneling microscope

  7. INSIDE AN ATOM

  8. NUCLEUS • 1 millionth of the volume of atom • 99.9% of the mass of an atom • very, very dense • contains: • protons • neutrons

  9. PROTON p+ • positive (+1) charge • mass = 1.673 x 10-24 g = 1 amu • amu = atomic mass unit • all identical • strong nuclear force holds them together

  10. NEUTRON n0 • NO charge • mass = 1 amu • all identical • the number of neutrons can vary for a specific element

  11. ELECTRON e- • negative (-1) charge • mass = 1/1836 of proton ≈ 0 amu • electron clouds: • space in which e- are likely to be found • e- whirl around nucleus billions of times per second • impossible to find the exact position of an electron • more energy means a larger electron cloud

  12. ATOM vs. ION • ATOM: • # of protons = # of electrons • NO CHARGE • ION: • A charged atom • e- < p+ indicates a POSITIVE ION “CATION” • e- > p+ indicates a NEGATIVE ION “ANION”

  13. SUBATOMIC PARTICLES Rutherford 1919 Chadwick 1932 Thomson 1897

  14. PERIODIC TABLE SYMBOL Element Name Atomic Number # of protons Element Symbol Atomic Mass (amu)

  15. Cr 52 24 ATOM SYMBOL (chromium-52) Mass Number # protons + # neutrons Atomic Number # of protons Element Symbol

  16. ATOMIC NUMBER “Z” • number of PROTONS • identifies the element • never, EVER changes for a given element

  17. MASS NUMBER “A” • number of PROTONS + NEUTRONS • mass of atom in amu (almost all mass is in the nucleus) • neutrons = mass number –atomic number

  18. ISOTOPE • atoms of the same element that have different numbers of neutrons (different mass numbers) • similar chemical properties, but different mass • isotopes are named for their mass number, for example: chlorine-35  35Cl chlorine-37  37Cl

  19. carbon-12: 6 protons 6 neutrons carbon-14: 6 protons 8 neutrons 12 6 14 6 C C ISOTOPE EXAMPLE

  20. ISOTOPE EXAMPLE

  21. Cr 52 24 ION SYMBOL Mass Number # protons + # neutrons Atomic Number # of protons Ion Charge +2 this atom must have LOST 2 ELECTRONS to become a +2 ION

  22. POSITIVE ION  CATION • atom that has lost electrons • Protons? 13 • Neutrons? 14 • Electrons? 10 Al +3 27 13

  23. NEGATIVE ION  ANION • atom that has gained extra electrons • Protons? 34 • Neutrons? 45 • Electrons? 36 Se -2 79 34

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