The Periodic Table Chapter 5

5.1 The periodic table Dimitri Mendeleev - publish first real periodic table - 1869 Based on chemical and physical properties Listed elements in increasing atomic mass order Left spaces for undiscovered elements His basic rule: the elements in any group, of the table are similar to their column-mates. Ex, look at the first column on the left, underneath hydrogen (H). The elements in this group are the alkali metals; they're all soft metals that react violently with water to make hydrogen gas.

…… Periodic Table aluminum Ga(1875) atomic mass 68 69.7 density 5.9 5.9 melting point low 29.8 Co oxide formula Al2O3 Ga2O3

….. Periodic Table Mendeleev formulated the original Periodic Law - Properties of elements are a periodic function of their atomic mass. 1911 - Mosely (English) discovers the proton so....new Periodic Law - Properties of elements are a periodic function of atomic number. *** History lesson - After his brilliant discovery, Mosely was drafted into the infantry to fight for the crown in WW I. He was killed. Only after the war was it realized that scientists should probably not be drafted into combat roles. That policy exists to this day.***

5.2 Electron configurations and the periodic table *** valence e- have largest effect on chemical/physical properties Label the groups/ families and periods

Names of Families Group 1 - Alkali Metals – They are not found alone in nature - why? explosive with water - they are stored under kerosene - very reactive. They react with nonmetals to form salts. They are silvery, shiny (luster), have a low melting point, and are soft (so soft, you can cut them with a knife). They are malleable (able to flattened into a sheet) and ductile (able to be drawn into a wire). Sodium and Potassium are particularly important in body chemistry.

…..Families Group 2 - Alkaline Earth Metals - 2nd most reactive elements. Also not “lone state” elements. Harder, denser than group 1. Common in sea salts.

…..Families Transition Metals - Groups 3-12. Harder, more brittle, higher melting point than groups 1 and 2. Form colored compounds. Conduct heat and electricity well and are shiny. Pd, Pt, Au - very unreactive (Noble metals). They can't be divided neatly into groups; all of them have very similar properties. Their valence electrons vary in chemical reactions. E.x. Iron (Fe), sometimes likes to give away 2e-, and sometimes 3e-.

…..Families Metalloids – B, Si, As, Te, At, Ge, Sb - stairs and 2 people under the stairs. Properties of metals and nonmetals. Brittle - used in semiconductors, computers.

….. Families Halogens - Group VII / 17 – most reactive of the nonmetals. Not found free in nature. Solids, liquids, and gases in this group. Widespread - sea salts, minerals, living tissue. Many applications - bleach, photography, plastics, insecticides.

….. Families Noble Gases - Group 18 – Least reactive elements - used in air conditioners, double pane windows, lights, balloons.

….. Families Lanthanides - f block rare earth elements (not really rare) - shiny, silver, reactive, make TV’s glow. Some have very interesting properties. For example, gadolinium (Gd) is the only rare earth that's ferromagnetic--that is, it sticks to magnets, the way iron does. Lanthanum is the only superconductor among them; at very low temperatures, it loses all resistance to the flow of electricity.

….. Families Actinides - f block Side note - unstable, radioactive - all but 4 are artificially created. Side note - f block elements are called inner transition elements - they were put into their current position by Glenn Seaborg - the only living person ever to have an element named after him.

5.3 Electron Configuration and Periodic Properties Periodic Trends: For all of the following periodic trends you should: know the definition be able to draw the trend on periodic table drawings with arrows explain why the trend happens relate the trend to other trends apply the trends on an “AB” sheet

Periodic Trends 2 trends 1. Atomic Radius - basic idea is “how big an atom is” - atoms are not spheres with outer boundaries due to the wave mechanical model. 2 trends size - natural, logical - add more shells size - not logical! why? from left to right - more protons are added, but not more shells. Higher charged nucleus pulls electrons closer.

Periodic Trends Atomic Radius BIGGER

Periodic Trends Atomic Radius Examples Which has a larger radius? Mg or Ca? F or B?

Periodic Trends 2. Electronegativity- basic idea - the ability of an atom to attract electrons (Linus Pauling) Electronegativity is related to atomic size…. They are opposites Trend Larger Larger

Periodic Trends Electronegativity Examples Which has a larger electronegativity? Cs or Mg? Mn or F?

Periodic Trends Trend: 3. Ionization energy - energy required to remove the most loosely held electron from the outer energy level of an atom. A(g) + energy yields A+(g) + e- Trend: Larger Larger

Periodic Trends IE is related to atomic radius - 2 reasons why smaller going down the table 1. greater distance from the nucleus - less attraction 2. inner electrons “shield” outer electrons from the nucleus Examples Which has a higher IE Se or Cl? B or Sr?

Periodic Trends Ionization Energy Cont’d There is also a 2nd and 3rd IE - always higher than the first. IE of elements greatly increases when the outer shell has been emptied. Example Which has a higher 2nd IE, Na or Mg? Which has a higher 3rd IE - Al or Mg? Mg Na

Periodic Trends 4. Electron Affinity - energy absorbed when an electron is acquired by a neutral atom. Basic idea - some atoms want to take on electrons - they have a high electron affinity value - they receive a lot of energy when accepting electrons Trend: Larger Larger

Periodic Trend Electron Affinity Cont’d Examples F or Na? F = -322 kJ/mole Na = -53 kJ/mole F has a higher electron affinity - higher, more negative value

Periodic Trends 5. Valence electrons - outer shell electrons involved with bonding –tells you about an element’s chemical behavior + Sodium Chlorine Salt

Periodic Trends Ions are created by gaining or losing electrons. 6. Ionic Radius - the size of an ion. Ions are created by gaining or losing electrons. Cation - positive, lost electrons Metals tend to become cations Anion - negative, gained electrons Nonmetals tend to become anions Cations are smaller than the neutral atom - why? they lost a shell Anions are larger - why? more electron repulsion so shells are pushed farther apart

Periodic Trends Ionic Radius Cont’d Trend Example Li+1 or Be+2 - Li is bigger because less protons pull the shell in less O -2 or N -3 - N is bigger because less protons pull the shell in less Larger Larger

Periodic Trends metals - larger atoms are more active - why? 7. Activity (Reactivity) metals - larger atoms are more active - why? they lose electrons more easily nonmetals - smaller more active - why? they gain electrons more easily

Periodic Table Metals Nonmetals Reactivity Trends Larger Larger Larger Most active metals + most active nonmetals = most stable compounds ex: RbF - very stable LiBr - less stable

Periodic Trends 8. Metallic character - some metals are said to be more metallic than others - really it is just a statement about their activity. If they are more active, they are said to be more metallic. Trend Which is more metallic? Ca or Na? Larger Larger