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The Structure of the Atom

The Structure of the Atom. The Building Block of Matter. Atoms are the smallest particles of an element that retains the chemical properties of that element. Parts: Nucleus – small region in the center of the atom. (+ charged protons, = charged neutrons)

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The Structure of the Atom

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  1. The Structure of the Atom The Building Block of Matter

  2. Atoms are the smallest particles of an element that retains the chemical properties of that element • Parts: • Nucleus – small region in the center of the atom. (+ charged protons, = charged neutrons) • Electron Cloud – large region, compared to nucleus, where electrons are found.

  3. Size of nucleus vs. electron cloud If an atom was the size of a sports stadium, the nucleus would be the size of a marble! Subatomic Particles: • Protons : + charge, relative mass = 1.007 atomic mass units (amu); round to 1 • Neutrons: = charge, relative mass = 1.009 atomic mass units (amu); round to 1 • Electrons: - charge, relative mass = 0.0005 atomic mass units (amu); round to 0 (not factored in when figuring total mass of an atom)

  4. Structure of Subatomic Particles • Subatomic particles composed of fast moving points of energy called quarks Quark Calculations(for protons and neutrons) Each proton is 2 up quarks and 1 down quark 2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1 Each neutron is 2 down quarks and 1 up quark 2(-1/3) + 2/3 = 0 Each electron is composed of 2 down quarks 3(-1/3) = -1

  5. Atomic Number • Number of protons in the nucleus (also the number of electrons) • Typically the number on top of the symbol on the Periodic Table. 13 Atomic Number 26.981

  6. Mass Number • Number of protons + number of neutrons in an atom. • When solving for number of neutrons: round mass number properly, subtract atomic number from mass number.

  7. Element Symbols • Hyphen Notation: Element symbol – Mass # (rounded) Example: Helium  He-4 • Nuclear Symbol: Superscript Mass Number, Subscript Atomic Number, Symbol Example: 4 He 2

  8. IONS • IONS are atoms or groups of atoms with a positive or negative charge. • Taking away an electron from an atom gives a CATION with a positive charge • Adding an electron to an atom gives an ANION with a negative charge. • To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O

  9. Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg2+ + 2 e- F + e- --> F-

  10. Isotopes • Atoms with the same number of protons & electrons but a different number of neutrons. • They are the same element, but have different masses. (different mass number) • All isotopes are used to calculate atomic mass (reason why weight is a decimal). • Most elements consist of a mixture of isotopes.

  11. 11B 10B Average Atomic Mass • Because of the existence of isotopes, the mass of a collection of atoms has an average value. • Boron is 20% 10B and 80% 11B. That is, 11B is 80 percent abundant on earth. • For boron average atomic mass = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu

  12. How to determine Average Atomic Mass • Determine Relative Abundance – % abundance divided by 100 • Determine weight of each isotope – multiply relative abundance by mass (keep all digits calculator gives you, no rounding yet) • Determine Average Atomic Mass - add up all individual weights, round to “2” decimal places

  13. How to determine Percent Abundance • Use the following equation: Ave. Atomic Mass = (X)(Mass of 1st isotope)+(1-X)(Mass of 2nd isotope) • Solve for “X” • Answer will be a decimal • To solve for other isotope, do 1 – answer • Multiply both answers by 100 • Two answer should equal 100

  14. Let’s see what you learned… Get your clickers ready!!!

  15. Which two subatomic particles are found in the nucleus of an atom? • Proton / Electron • Proton / Neutron • Electron / Neutron • Proton / Quark • Neutron / Quark

  16. The atomic number represents the number of … • Protons • Neutrons • Protons + Neutrons • Protons + Electrons

  17. The mass number represents the number of … • Electrons • Protons + Electrons • Protons + Neutrons • Neutrons + Electrons

  18. What is the correct Hyphen Notation for Calcium • Ca – 20 • Ca – 40.078 • Ca – 40.08 • Ca – 40.1 • Ca - 40

  19. An atom has 14 protons and 20 neutrons. The element is … • Si • Ca • Se • C

  20. An atom has 15 protons and 17 neutrons. What element is it? • Cl • He • Ge • P

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