The Periodic Table Chemistry

 Stanislao Cannizzaro ( ) Found a method to determine atomic mass Found a method to determine atomic mass  Dimitri Mendeleev ( ) “Father of the Periodic Table” “Father of the Periodic Table” Made the first accepted Periodic Table Made the first accepted Periodic Table Noticed trends and left empty spaces for “missing” elements Noticed trends and left empty spaces for “missing” elements **By 1860 more than 60 elements were known****By 1860 more than 60 elements were known**

 Henry Moseley (1887 – 1915) Found a method to determine atomic number (# of protons) Found a method to determine atomic number (# of protons)

 Periodic Law Properties of elements are based on atomic number and valence electrons Properties of elements are based on atomic number and valence electrons  The Modern Periodic Table Arranged by increasing atomic number so elements with similar properties fall in the same columns Newest sections added: Lanthanides, Actinides, Noble Gases

 Valence Electrons: Outer Shell Electrons Outer Shell Electrons Have the Highest Principle Quantum Number Have the Highest Principle Quantum Number Determine many properties of the atoms Determine many properties of the atoms Were the “dots” on the dot diagram from last chapter! Were the “dots” on the dot diagram from last chapter!

 Periodic Table Arrangement: Period# of Elements Energy Sublevel Max # of Electrons 12s2 28s,p s,p,d18 5 s,p,d18 632s,p,d,f32 7 (if finished) 32s,p,d,f32

 Using only the ELECTRON CONFIGURATION… Example: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3 Located in PERIOD 4 Highest Principle QN

 Using only the Electron Configuration… Example: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3 Located in Group 15 – Add the electrons from the highest period (includes s, d if any, and p if any)

 s – Block Group 1 = Alkali Metals Group 1 = Alkali Metals  Soft  Extremely reactive  (but…Hydrogen is NOT a metal)  1 valence electron

 s-Block Group 2 = Alkaline-Earth Metals Group 2 = Alkaline-Earth Metals  2 valence electrons  Reactive but less than Group 1

 p block: Groups Groups Properties vary greatly Properties vary greatly (due to “steps”)(due to “steps”) Valence Electrons = Valence Electrons = Group # - 10Group # - 10 Example: Example:

 p block: Group 17 = Halogens Group 17 = Halogens  Very reactive A halogen lamp also uses a tungsten filament, but it is encased inside a much smaller quartz envelope. Because the envelope is so close to the filament, it would melt if it were made from glass. The gas inside the envelope is also different -- it consists of a gas from the halogen group. These gases have a very interesting property: They combine with tungsten vapor. If the temperature is high enough, the halogen gas will combine with tungsten atoms as they evaporate and redeposit them on the filament. This recycling process lets the filament last a lot longer. In addition, it is now possible to run the filament hotter, meaning you get more light per unit of energy. You still get a lot of heat, though; and because the quartz envelope is so close to the filament, it is extremely hot compared to a normal light bulb.

 p block: Group 18 = Noble Gases Group 18 = Noble Gases  Very unreactive  They have a stable (full) valence octet  Many used in creating signs Neon signs are luminous-tube signs that contain neon or other inert gases at a low pressure. Applying a high voltage (usually a few thousand volts) makes the gas glow brightly. They are produced by the craft of bending glass tubing into shapes. A worker skilled in this craft is known as a glass bender, neon or tube bender.

 d block: Groups 3-12 Groups 3-12 Called the TRANSITION METALS Called the TRANSITION METALS Luster, conductive, Malleable, Ductile Luster, conductive, Malleable, Ductile Hg is the ONLY liquid metal Hg is the ONLY liquid metal

 f Block Lanthanides Actinides

 “Trends”  Strength of Nucleus A. Across a period – strength gets stronger  Atomic Number!! More protons = greater charge on nucleus B. Down a group – strength gets weaker  Size of atom is getting larger – e - in levels farther away – shielding attraction from nucleus

 Atomic Radius (size of atom) A. Across a period – radius gets smaller  Decreases across periods because of increasing positive charge  e - are pulled closer to a higher charged nucleus  Increased pull results in a smaller atomic radius B. Down a group – radius gets bigger  Outer e - fill an s sublevel in a higher energy level farther from the nucleus

Energy to REMOVE an electron  Ionization Energy - Energy to REMOVE an electron ION – atom that has gained or lost an electron ION – atom that has gained or lost an electron A. Across a period – ionization energy increases  Increasing nuclear charge – pulls e - toward nucleus  Harder to pull away because of strong attraction B. Down a group – ionization energy decreasesB. Down a group – ionization energy decreases  Outer e - are farther away from nucleus – more easily removed.  Outer e - are also shielded from positive nucleus – weak attraction – easily removed

 Electron Affinity – Energy change when an electron is ADDED Energy change when an electron is ADDED  When EASY to add an electron – EA is EXOTHERMIC / NEGATIVE  When DIFFICULT to add an electron – EA is ENDOTHERMIC / POSITIVE A. Across a period – EA is easier/more exothermic B. Down a group – EA is difficult/more endothermic FYI - Generally more difficult to add e - to larger atoms!!FYI - Generally more difficult to add e - to larger atoms!!

 Ionic Radius Size of ion Same trend as atomic radius:  Across a period – gets smaller  Down a group – gets bigger

 Ionic Radius Size of ion Cation – Lost electrons  Positively charged ion due to less electrons, so nucleus can pull better on each e -  Smaller than neutral atom; due to less electrons, so nucleus can pull better on each e - Potassium Atom Potassium ION

 Ionic Radius Size of ion Anion – Gained electrons  Negatively charged ion due to more electrons, so nucleus can’t pull as well on each e -  Larger than neutral atom; due to more electrons, so nucleus can’t pull as well on each e -

 Electronegativity Ability to attract electrons A. Across a period – EN increases B. Down a group – EN decreases FYI:  Nonmetals are always more electronegative!!  Larger atoms attract e - less strongly

 Which is smaller – C or O?  Which is larger – Be or Be +2 (Neutral Be atom or Be ion)?  Which has a more exothermic electron affinity – Na or P?  Which has a more endothermic electron affinity – K or Cs?  Which has a higher ionization energy – Ga or Se?  Which has a higher electronegativity – F or Br?