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Periodicity & the Periodic Table The Atom in 1869 – Dmitri Mendeleev The First “Modern” Periodic Table The Atom in 1869 – Dmitri Mendeleev Mendeleev’s “Periodic” Atomic Theory • Elements of similar atomic mass display similar properties • Elements with atomic masses that increase in equal increments display similar properties • The elements can be arranged 2dimensionally by their properties to predict “missing” elements. Think you’re as smart as Mendeleev? Periodicity I’m a genius! Elements display repeating patterns based on their properties when arranged into a 2-dimensional grid Think you’re as smart as Mendeleev? The basic idea: arrange cards so that patterns and trends follow logical orders across and up/down your table. Find missing boxes by finding "gaps" in the trends. Predict what's missing. B1 C1 A2 B2 C2 B3 A1 D1 D3 D2 A3 The basic idea: arrange cards so that patterns and trends follow logical orders across and up/down your table. Find missing boxes by finding "gaps" in the trends. Predict what's missing. A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 D3 The basic idea: arrange cards so that patterns and trends follow logical orders across and up/down your table. Find missing boxes by finding "gaps" in the trends. Predict what's missing. A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3 Alien Periodic Table • Arrange the cards you have been given into a grid- It will be a rectangle • Aliens that demonstrate similar properties are adjacenteither side to side or under and over. The Modern Periodic Table The Modern Periodic Table What it REALLY looks like! GROUPS Group Numbers Remember periodicity? How do Groups relate to periodicity? NO Group Numbers (Names Only) PERIODS Period Numbers And how does periodicity relate to periods? 6.2 Classification of the Elements • Elements can be classified into four categories based upon their electron configurations 1.Noble gases • He, Ne, Ar, Kr, Xe, and Rn • Full outer s and p sublevels 2. Representative elements • Groups 1A – 8A (this includes Noble Gases) • Partially filled s and p sublevels 6.2 Classification of the Elements 3. Transition metals • • 4. d block Outer s and nearby d sublevel contain electrons Inner transition metals • • f block Outer s and nearby f sublevel contain electrons Noble Gases Transition Metals Representative Elements Inner Transition Metals GENERAL CATEGORIES Yeah. You gotta know ‘em. General Properties Usually, metals are: • Conductive • Shiny • Malleable • Ductile • Solid at room temperature (can you think of an exception?) The Alkali Metals are particularly interesting: • Very soft, cut with a knife • Highly reactive with air and water General Properties Usually, non-metals are: • Insulators • Dull • Brittle • Often gaseous at room temperature The Noble Gasses are particularly interesting: • Exceptionally Nonreactive The Halogens are also very interesting: • Tend to form diatomic molecules • Highly reactive with almost everything General Properties Metalloids: • Some are like metals • Some are like non-metals • Properties vary greatly within a group FAMILIES Yeah. You gotta know ‘em. What is similar for all elements in a group or family? These have 1 These have 3 They have the same number of outer level Classification of the Elements Electrons, particularly the valence electrons, control many of the chemical and physical properties of atoms! 6.3 Periodic Trends • Because the arrangement of elements on the periodic table is closely linked to the electron configuration, there are a number of trends that can be used to predict chemical and physical behavior. • In order to understand and use these trends, you must first understand how NUCLEAR CHARGE and SHELLS AND SHIELDING influence electron behavior. ALL TRENDS ARE EXPLAINED BY NUCLEAR CHARGE AND SHELLS AND SHIELDING 6.3 Periodic Trends • Nuclear Charge • As you move across a period or down a group, the atomic number increases. • This means the number of protons in the nucleus is increasing. • With more protons, the positive pulling strength (nuclear charge) of the nucleus is increasing Nuclear Strength Increases Increases 6.3 Periodic Trends • Shells • Energy levels • The higher the level, the farther from the nucleus • Across – highest energy does not change • Down – energy levels increase • Shielding • Inner level electrons interfere or shield the valence electrons from the nucleus • Across – shielding is constant • Down – shielding increases Shells and Shielding Constant Increases Nuclear Charge verses Shells and Shielding • Period Trend • Nuclear Strength Wins!!! • Because Shells and Shielding are constant across a period they don’t affect period trends • Therefore, ALL PERIOD TRENDS are caused by increasing nuclear charge. Nuclear Charge verses Shells and Shielding • Group Trend • Shells and Shielding Win • Even though nuclear charge is increasing, more Shells (your farther from the nucleus) and Shielding (inner level electron interference) decreases the effective nuclear strength. • Therefore, ALL GROUP TRENDS are caused by shells and shielding or their effect on the nuclear charge. Nuclear Charge verses Shells and Shielding S/S Increases lowering effective Nuclear Strength Nuclear Strength Increases Atomic Radius • Atomic radius – estimated as ½ the distance between the nuclei of 2 like atoms in a diatomic molecule. As atomic radius increases, the element increases in size. Atomic Size Atomic Size Size Decreases Size Increases Ion Formation • Octet Rule – atoms will gain or lose electrons (sometimes even sharing like in molecules) to acquire a full set of 8 valence electrons. • Metals will lose electrons • Nonmetals gain electrons Two hydrogen atoms are walking down the street. Hey, I think I just lost an electron! Are you sure! Yeah! I’m POSITIVE! Ion Formation • Cation – formed when electrons are removed from a neutral atom • Nucleus has a stronger pull on the remaining electrons decreasing the size The Cation is smaller than the neutral atom! Ion Formation • Anion – formed when electrons are added to a neutral atom • Nucleus has a weaker hold on the increased number of valence electrons and the ion size increases The Anion is larger than the neutral atom! Ion Size • Period Trend • Cations and Anions both decrease in size across a period • Group Trend • Cations and Anions both increase in size down a group Ionic Size Cations decrease Anions decrease Both increase Ionization Energy • Ionization energy – energy needed to remove an electron from an atom Na(g) Na+(g) + e- Ionization Energy • To remove an electron you have to overcome the nucleus’ hold on the electron. • 1st Ionization Energy – Energy needed to remove first electron. • 2nd Ionization Energy – Energy needed to remove a second electron. • This is always higher than the 1st ionization energy. • When an electron is removed, the nucleus has a stronger hold on the remaining electrons. • When you have a noble gas electron configuration it becomes very difficult to remove an electron. Ionization Energy Ionization Energy • Group Trend • Decreases as you go down a group 1. 2. • The farther the outer electrons are farther from the nucleus, the weaker the pull. The inner level electrons block the nucleus’ ability to attract the valence electrons. Period Trend • Increase as you go across a period Ionization Energy 1st Ionization Energy decreases 1st Ionization Energy increases Electronegativity • Electronegativity – attraction of one atoms nucleus to another atoms electrons when they are chemically bonded H O H Water Molecule Measure of how strong the oxygen nucleus attracts the hydrogen’s electron Electronegativity H 2.1 Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 K 0.8 Ca 1.0 Ga 1.6 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Rb 0.8 Sr 1.0 In 1.7 Sn 1.8 Sb 1.9 Te 2.1 I 2.5 Cs 0.7 Ba 0.9 Tl 1.8 Pb 1.9 Bi 1.9 Electronegativity • Period Trend • Increases across a period • Greater hold on electrons • Group Trend • Decreases down a group • Weaker hold on the electrons Electronegativity Electronegativity increases Electronegativity decreases Designing A Periodic Table Activity • Arrange the cards you’ve been given into a grid. Your grid may or may not be perfectly square. • Atoms with similar properties are adjacent, either side to side or over and under. • There may be “gaps” where an element should be to make the similarity of properties make sense. Put your blank card in the gap. • When you’ve found the missing element, interpolate its properties from its neighbors