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Unit 2 Materials: Structure and Use

Unit 2 Materials: Structure and Use. Section A Why We Use What We Do. A.6 – The Periodic Table. History: Dimitri Mendeleev (Russian) – 1869 Early design of the periodic table Original periodic tables were arranged according to mass and “combining capacity”

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Unit 2 Materials: Structure and Use

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  1. Unit 2Materials: Structure and Use Section A Why We Use What We Do

  2. A.6 – The Periodic Table • History: • Dimitri Mendeleev (Russian) – 1869 • Early design of the periodic table • Original periodic tables were arranged according to mass and “combining capacity” • Mass  relative to other elements (ex: oxygen is 16 times more massive than hydrogen) • Combining capacity  the way elements combine with atoms of another element (ex: 1 atom of K combines with 1 atom of Cl; 1 atom of Ca combines with 2 atoms of Cl) • Also based on chemical and physical properties

  3. More Mendeleev… Mendeleev left spaces for undiscovered elements • Eka - Aluminum Ga (1875) • atomic mass 68 69.7 • density 5.9 g/cm3 5.9 g/cm3 • oxide formula E2O3 Ga2O3 • also predicted Eka - Silicon – Germanium • Mendeleev formulated the original Periodic Law - Properties of elements are a periodic function of their atomic mass. • 1911 - Mosley (English) discovers the proton so.... • new Periodic Law - Properties of elements are a periodic function of atomic number.

  4. A.8 – The Pattern of Atomic Numbers • Recall: All atoms are composed of • Protons  positive charge • Neutrons  neutral charge • Electrons  negative charge e- nucleus p+ n0 e- electron cloud e- e-

  5. A.8 – The Pattern of Atomic Numbers

  6. A.8 – The Pattern of Atomic Numbers • ATOMIC NUMBER = the number of protons in one atom of an element – this is also the number of electrons if the atom is not charged • The atomic number (# of p) is what distinguishes one element from another • Examples: • Na = sodium • Atomic number 11  11 protons • C = carbon • Atomic number 6  6 protons

  7. A.8 – The Pattern of Atomic Numbers • You try… • How many protons does one atom of Cl have? • What element has 28 protons?

  8. A.8 – The Pattern of Atomic Numbers • The total mass of an element is determined by the combined number of protons and neutrons and in the nucleus. • ATOMIC MASS NUMBER = #p + #n • ( round the atomic mass to the nearest whole #) • Electrons = 1/1837th the mass of a p or n • does not significantly contribute to the mass of the atom.

  9. A.8 – The Pattern of Atomic Numbers • Examples: • Carbon mass = 12.0111 mass # = 12 # protons = 6 (atomic # of C) (also 6 electrons) # neutrons = mass # - # p = 12 – 6 = 6 2. Aluminum mass = 26.98 mass # = 27 # protons = 13 (atomic # of Al) (also 13 electrons) # neutrons = 27 – 13 = 14

  10. A.8 – The Pattern of Atomic Numbers • ATOMIC WEIGHT (Atomic Mass) – average mass of an atom of an element “as found in nature” • To determine mass number from Periodic Table: • Round the atomic weight to the nearest whole number • Examples: Beryllium • atomic weight = 9.01 (PT) • mass number = 9 Phosphorus • atomic weight =30.97 • mass number = 31

  11. Ions • Ions – atoms with a charge • Ions are created by gaining or losing electrons • There is a pattern on the periodic table to know: • +1,+2,+2222222222,+3,+/-4,-3,-2,-1,0 • + ions are called cations • - ions are called anions

  12. A.8 – The Pattern of Atomic Numbers (ions) • You try… • Mg (+2 charge) mass # = # protons = _______ # neutrons = _______ # electrons = _______ 2. F (-1 charge) mass # = # protons = _______ # neutrons = _______ # electrons = _______

  13. A.8 – The Pattern of Atomic Numbers • All atoms of the same element have the same number ofprotons. However… • The number of neutrons can differ from atom to atom of an element. • Example:Carbon • All atoms of carbon contain 6 protons. • But they can contain 6, 7 or 8 neutrons. • Therefore, carbon can exist as any one of three forms… • Mass # = 12, Mass # = 13, Mass # = 14

  14. A.8 – The Pattern of Atomic Numbers • ISOTOPES – DIFFERENT VERSIONS of the SAME ELEMENT with DIFFERENT MASSES because they have DIFFERENT NUMBERS OF NEUTRONS. • Atoms of the same element with different mass numbers • Ex: • C-12, C-13, C-14 (12C, 13C, 14C)

  15. A word on how to write all the information about atoms…. • An element can be written on a piece of paper like this…. • Or this…. • Or this…. • Ions are shown like this…. • Or this…. • Or this….

  16. A.10 – Organization of the Periodic Table Groups (Families) Periods

  17. A.10 – Organization of the Periodic Table Group 17: Halogens (Red) Group 2: Alkaline Earth Metals (Purple) Group 18: Noble Gases (Lt. Blue) Group 1: Alkali Metals (Yellow) Transition Metals

  18. A.10 – Organization of the Periodic Table Let’s label metals, nonmetals, and metalloids

  19. A.10 – Organization of the Periodic Table • Alkali Metals – Group 1 • Highly Reactive • Forms ECl chloride • E = one atom of element • ex: NaCl, KCl • Forms E2O oxide • Ex: Na2O, Li2O • Alkaline Earth Metals – Group 2 Less Reactive, forms ECl2 chloride, Forms EO oxide

  20. A.10 – Organization of the Periodic Table • Noble Gas Family – Group 18 • Unreactive (Inert) • Halogen Family – Group 17 • Very reactive - Readily form ions (-1) • Metalloids – “the staircase” B, Si, As, Te, At, Ge, Sb • Properties of metals and nonmetals • Transition Metals – Groups 3-12 • Hard, dense, high melting points • Elements in the same GROUP will have similar chemical properties

  21. A.10 – Organization of the Periodic Table • Which elements are more alike? 1. Chlorine and Phosphorus or Chlorine and Iodine 2. Magnesium and Sodium or Potassium and Sodium 3. Arsenic and Antimony or Arsenic and Phosphorus or Arsenic and Germanium

  22. A.11 – Predicting Properties • Elements in the same GROUP/ FAMILY will have similar chemical properties • We can use the placement of each element on the periodic table to predict its properties. • Ex: (pg 126) – Given: Density of Si = 2.3 g/cm3 Sn = 7.3 g/cm3 Estimate the density of Germanium

  23. A.11 – Predicting Properties • Where are Si, Sn and Ge located on the Periodic Table? • Same Group • To Solve – average the two known densities together. • (2.3 g/cm3 + 7.3 g/cm3) / 2 = 4.8 g/cm3 estimated density of Ge We can also do this for melting point estimates!!!

  24. A.11 – Predicting Properties • Formulas can be predicted from relationships within the PT • Ex: Carbon dioxide = CO2 What is the formula for a compound of carbon and sulfur? O and S in the same group, therefore CS2 But.... There is a lot easier way!!!! Remember????

  25. Writing Formulas for Binary Ionic Compounds • If the charges are the same, they cancel • Examples……. • If the charges are different, “criss cross” (apple sauce?) • Examples…….

  26. A.11 – Predicting Properties • Answer the questions on page 126 in the space provided on your notes outline. • When finished, check your answers • – 149 °C 2 a.320 Kb.sodium higher 3. GeCl4 4 a. CF4b. Al2S3c. KCl d. CaBr2e. SrO

  27. A. 13 It’s Only Money • High melting point, malleability, identifiable color. • Appropriate size, mass, and shape (to use in coin vending machines). • Resistance to corrosion. Ability to form alloys. • Nonreactivity with other metals, water, air, etc. • Metals – we’ve been using them for a long time on this planet. • Durability, lack of reactivity, hardness, etc.

  28. A.12 – What Determines Properties? • The Physical and Chemical properties of an element are governed by the number and arrangement of the atom’s electrons. The electrons in the outer shell are most important! • 1, 2, 2222222222, 3, 4, 5, 6, 7, 8 • Metals  lose electrons to form cations (+) • Nonmetals  gain electrons to form anions (-) • The charges on the columns are…. • +1, +2, +2222222222, +3, +/-4, -3, -2, -1, 0 • Metals have stronger attractions between atoms than nonmetals  higher melting points than nonmetals

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