Chapter 5 The Periodic Table

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

History of the Periodic Table  Henry Moseley (1887 – 1915) Found a method to determine atomic number (# of protons)

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

Electron Configurations Revisited Valence Electrons: -Outer Shell Electrons -Have the Highest Principle Quantum Number -Determine many properties of the atoms Example: Arsenic:

Electron Configurations Revisited Periodic Table Arrangement: s orbital p orbital d orbital f orbital

Period Prediction 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 (the highest principle quantum number)

Group Prediction 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)

Blocks on the Periodic Table s block: Group 1 = Alkali Metals Soft Extremely reactive (but…Hydrogen is NOT a metal) 1 valence electron

Blocks on the Periodic Table s block: Group 2 = Alkaline-Earth Metals 2 valence electrons Reactive, but less than Group 1 (Go down to “Video clip” half way down page)

Blocks on the Periodic Table p block: Groups Properties vary greatly (due to “steps”) Valence Electrons = Group # - 10 Example:

Blocks on the Periodic Table p block: 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. (

Blocks on the Periodic Table p block: 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. (

Blocks on the Periodic Table d block: Groups 3-12 Called the TRANSITION METALS Luster, conductive, Malleable, Ductile Examples: Hg is the ONLY liquid metal Keep Your Paws Off Mercury video

Blocks on the Periodic Table f block: (Layout can vary slightly) Lanthanides Actinides

Periodic Properties (aka TRENDS) 1. Strength of the Nucleus STRONGER

Why does it increase across periods? Atomic Number!! More protons = greater charge on nucleus

Periodic Properties (aka TRENDS) 1. Strength of the Nucleus WEAKERWEAKER

Why does it decrease down groups? Size of atom is getting larger e - in levels farther away Shielding attraction from nucleus

Periodic Properties (aka TRENDS) 2. Atomic Radius (size of an atom) SMALLER

Why does it decrease across periods? Decreases across periods because of increasing positive charge e - are pulled closer to a higher charged nucleus Increased pull results in a lower atomic radius

Periodic Properties (aka TRENDS) 2. Atomic Radius LARGERLARGER

Why does it increase down groups? Outer e - fill an s sublevel in a higher energy lever farther from the nucleus

2. Atomic Radius

Periodic Properties (aka TRENDS) ION = Atom with a charge due to gain or loss of (an) electron(s) 3. Ionization Energy (Energy to REMOVE an electron) Increases

Why does it increase across periods? Increasing nuclear charge – pulls e - toward nucleus Harder to pull away because of strong attraction

Periodic Properties (aka TRENDS) 3. Ionization Energy Decreases

Why does it decrease down groups? Outer e - are farther away from nucleus – more easily removed. Outer e - are also shielded from positive nucleus – weak attraction – easily removed

Periodic Properties (aka TRENDS) 4. Electron Affinity (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

Periodic Properties (aka TRENDS) 4. Electron Affinity Easier / More Exothermic

Periodic Properties (aka TRENDS) 4. Electron Affinity More Difficult / More Endothermic

FYI Generally more difficult to add e - to larger atoms!!

Periodic Properties (aka TRENDS) 5. Ionic Radius (Size of ion) Cation = LOST electron(s) Has POSITIVE charge SMALLER than the neutral atom – due to less electrons, so nucleus can pull better on each e - Potassium Atom = 19 protons and 19 electrons Potassium ION = 19 protons and 18 electrons Lost 1 electron Now ALL of these electrons get pulled in a little bit!

Periodic Properties (aka TRENDS) 5. Ionic Radius (Size of ion) Anion = Gained electron(s) Has NEGATIVE charge Larger than the neutral atom – due to more electrons, so nucleus can’t pull as well on each e - The extra e-. Now all of the electrons move out a little bit.

Periodic Properties (aka TRENDS) 6. Electronegativity - Ability to attract electrons Higher

Periodic Properties (aka TRENDS) 6. Electronegativity Decreases

FYI Nonmetals are always more electronegative!! Larger atoms attract e - less strongly

Graphing of Trends

Example Questions 1. Which is smaller – C or O? 2. Which is larger – Be or Be +2 (Be ion)? 3. Which has a more exothermic electron affinity – Na or P? 4. Which has a more endothermic electron affinity – K or Cs? 5. Which has a higher ionization energy – Ga or Se? 6. Which has a higher electronegativity – F or Br?