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Introduction to Atoms

Chapter 6 State Standards: 3.a; 7.b. Introduction to Atoms. The Atom. Chapter 6-2 (Part 1). Developing the Atomic Theory. There have been many changes that have contributed to what the atomic theory is today Over centuries many scientist have discovered and clarified information

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Introduction to Atoms

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  1. Chapter 6 State Standards: 3.a; 7.b Introduction to Atoms Contreras

  2. The Atom Chapter 6-2 (Part 1) Contreras

  3. Developing the Atomic Theory • There have been many changes that have contributed to what the atomic theory is today • Over centuries many scientist have discovered and clarified information about the atom Contreras

  4. The Atom • The atom is the smallest particle within an element • An element is made-up of MANY atoms that are exactly the same • Atoms cannot be seen with the naked eye It would take 106 million billion Au atoms to cover the surface of a dollar bill 70 million He atoms could fit on your pencil eraser Contreras

  5. Parts of an Atom (Subatomic Particles) • Nucleus – small, dense, positively charged center • Protons – positively charged particles in the nucleus • Neutrons – particles in the nucleus with no charge • Electrons – negatively charged particles found in electron clouds outside the nucleus. Determines size of atom. Contreras

  6. Parts of an Atom Electron Cloud Contreras

  7. Inside the Nucleus 1 amu = 0.0000000000000000000000017 g Atomic Mass Unit (amu) • Protons • 1 amu • Positively charged (+) • Neutron • 1 amu • No charge • The nucleus is the biggest part of the atom • If there was a nucleus the size of a grape, it would have a mass of 9 million metric tons (18 million pounds)! Contreras

  8. Outside the Nucleus • Electrons • Negatively charged (-) • Found only in electron clouds • Smallest mass particle of the atom • 1/1800 size of proton and neutron • Electron Cloud • Region outside the nucleus where electrons are contained Contreras

  9. Atoms and Elements Chapter 6-2 (Part 2) Contreras

  10. Forces within Atoms • Gravitational Force – holds all the parts of the atom together • Electromagnetic Force – attracts electrons (-) around nucleus (+) • Strong Force – holds protons in nucleus together • Weak Force – holds nucleus together in radioactive atoms Contreras

  11. Charges • Nucleus has a positive charge (because of protons) • Electrons have negative charge • For an atom to have no charge, positive and negative charges need to be balanced (# of protons and electrons is equal) • An ion is an atom with a charge • Positively charged ion = atom has lost 1+ electron(s) • Negatively charged ion = atom has gained 1+ electron(s) Contreras

  12. Atoms and Elements • Atomic number - # of protons in nucleus • Atomic number (# of protons) is the same for all atoms of a certain element • Atomic number tells you what element it is! • Atomic mass (mass number) = protons + neutrons • Atomic mass needs to be rounded Atomic mass Contreras

  13. Electron Cloud Locations Contreras

  14. So far we know… • An element’s atomic number tells where it is on the periodic table Atomic number = # protons (+) # protons (+) = # electrons (-) • As long as the atom is not an ion Atomic mass = protons + neutrons Contreras

  15. Isotopes Chapter 6-2 (Part 3) Contreras

  16. Isotopes • Atoms of the same element that have different number of neutrons in their nucleus • Isotopes still have same: • Atomic number • # protons • # electrons • Different # neutrons • Named according to the mass number • hydrogen-1 and hydrogen-2 Contreras

  17. Example of an Isotope • Hydrogen has an atomic number of 1 • So Hydrogen has 1 proton • Hydrogen has 2 additional isotopes (H with different number of neutrons) • Deuterium (1 proton & 1 neutron) • Tritium (1 proton & 2 neutrons) Contreras

  18. Finding the # of Neutrons • To find the number of neutrons: • Protons + neutrons = mass number • Mass number – atomic number (# proton) = neutrons • Mass numberof Carbon is 12 Mass number: 12 Atomic number: - 6 # Neutrons: ~6 Contreras

  19. Radioactive Isotopes • An unstable atom where the nucleus will change and eventually fall apart over time • Will give off energy when they fall apart • Ex. Radon; Uranium • Found in nature • No stable isotope exists http://computershopper.com/shoptalk/Radioactive_Man_Number_One_v_1024.jpg Contreras

  20. Remember… • Ions have a charge • Positive charge if lost an electron • K 1+ has lost an electron • Negative charge if gained an electron • Cl 2- has gained two electrons • Isotopes • Have same number of protons & electrons, different number of neutrons Contreras

  21. smallest mass biggest mass electron  proton/neutron  nucleus  atom  element Contreras

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