Chemistry Riddle Q: What is a robber’s least favorite element? A: Copper!!!

Introduction to Periodic Trends

Remember these groups of the periodic table?

The Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Classifying Elements by Electron Configuration Remember…electrons play the most significant role in determining physical and chemical properties of elements. Elements are arranged in the table according to their properties. Therefore, there should be some relationship between the electron configurations of the elements and their placement in the table.

How the configurations of the noble gases similar? 1s22s22p6 1s22s22p63s23p6 1s22s22p63s23p64s23d104p6 1s22s22p63s23p64s23d104p65s24d105p6 1s22s22p63s23p64s23d104p65s24d10 5p66s24f145d106p6 2 Ne 10 The outer energy level is completely full! Ar 18 Kr 36 Xe 54 Rn 86

How are the configurations of the alkali metals similar? 1 Li 3 Na 11 K 19 Rb 37 Cs 55 Fr 87 1s1 1s22s1 1s22s22p63s1 1s22s22p63s23p64s1 1s22s22p63s23p64s23d104p65s1 1s22s22p63s23p64s23d104p65s24d10 5p66s1 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1 They all end in s1!

Alkaline earth metals all end in s2. He s2 Alkaline earth metals might include He, but He fits better with the noble gases. He has similar properties to the noble gases because its outer energy level is completely full. How would the halogens all end? p5

Periodic Trends These patterns in electron configurations produce patterns in properties. These patterns are called Periodic Trends. Can be followed either across a period or down a group

Five Trends Atomic Size Ion Size Ionization Energy Electron Affinity Electronegativity

Influenced by two factors: 1. Energy level Periodic Trends Influenced by two factors: 1. Energy level At higher energy levels the electron is further away from nucleus. 2. Charge on nucleus (# protons) More protons means a greater charge pulls electrons in closer.

Problem: Where do you start measuring from? Trends in Atomic Size Problem: Where do you start measuring from? The electron cloud doesn’t have a definite edge. This problem is solved by measuring more than 1 atom at a time.

} Trends in Atomic Size Radius Measure the distance between the two nuclei of a diatomic molecule. Half of this distance is the atomic radius.

Atomic Size - Group Trend H As we go down a group… Each atom has another energy level So the atoms get bigger. Li Na OBVIOUS!! K Rb

Atomic Size - Period Trend Going from left to right across a period, the size gets smaller. Electrons are in the same energy level. But, there is more nuclear charge (more protons). So…outermost electrons are pulled in closer. NOT SO OBVIOUS!! Na Mg Al Si P S Cl Ar

Atomic radius increases Atomic radius decreases Atomic radius increases

Ionization Energy Electronegativity Electron Affinity Periodic Trends, Cont. Ion Size Ionization Energy Electronegativity Electron Affinity

Ion Size To form ions, atoms may gain or lose electrons. If an atom loses electrons, a positive ion is formed called a cation. Metals tend to lose electrons. This cation is smaller than the atom from which it formed. It now has fewer occupied energy levels.

Ion Size When an atom gains electrons, a negative ion is formed called an anion. Nonmetals tend to gain electrons. This anion is larger than the atom from which it was formed. The period and group trends for ions are the same as atomic radius….except in the period trend when you cross the metal-nonmetal dividing line.

Ion Size Period Trend N3- O2- F1- B3+ Li1+ Be2+ C4+ Cations—Atoms that have lost electrons to become positively charged. Anions—Atoms that have gained electrons to become negatively charged. Smaller than the original, but showing the same trend in size. Larger than the original, but showing the same trend in size.

Ionization Energy The amount of energy required to completely remove an electron from an atom. Removing one electron makes a +1 ion The energy required to remove the outermost electron is called the first ionization energy. Also known as…IE

Ionization Energy Trends As you go across a period… The electrons are closer to the positive nucleus and therefore harder to pull off. The harder it is to pull off the electron, the higher the ionization energy.

Ionization Energy Trends As you go down a group… The electrons are farther away from the positive nucleus and therefore easier to pull off. There are more electrons shielding the outer electrons from the positive nucleus, making them easier to pull off. The easier it is to pull off the electron, the lower the ionization energy.

Ionization Energy Trends (Generally) Increases Decreases

Ionization Energy Graph

Electron Affinity Trends Ability for a neutral atom to acquire an electron is known as it’s Trend: Increase across the period Hence the high reactivity of Halogen No general trend for the groups Electron Affinity

Electron Affinity Trends Increases Noble Gases do not have an affinity for electrons. NO definite pattern

Electronegativity The tendency for an atom to attract electrons to itself when it is chemically bonded to another element(s). Measures how fair an atom shares electrons. Large electronegativity means it pulls the electron toward it strongly. Fluorine is the most electronegative element

Electronegativity Trends Increases Noble Gases are not electro-negative. F Fluorine is the most electronegative element. Decreases

Chemistry Riddle Give this flask to Mel and tell him to put it away where no one can find it. What is it? It’s formaldehyde!!

Diatomic Molecules 7 elements Beginning with element 7 Form the number 7 (except H) Never alone If they are not with another element, they bond with themselves. 1 H He 2 Li Be S C N O F Ne 3 Na Mg Al Si P Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La   Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Uub — Uuq 7

Chemistry Riddle Q: What does a doctor do with a sick chemist? A: He!