2 The Big Idea…Nuclear Charge – the effect protons of an atom have on its size and shape.
3 I. Trends in Atomic Size A. Atomic Radius 1. Def – one half of the distance between the nuclei of two like atoms in a diatomic molecule.-radius = from center toouter edge2. Measured in picometers (pm)-1 x m3. Measured in angstroms (Å)-1 x m
5 3. The distance between the nuclei of two covalently bonded flourine atoms is 128 pm. What is the atomic radius of 1 fluorine atom?4. The distance between the nuclei of two covalently bonded nitrogen atoms is 142 pm. What is the atomic radius of 1 nitrogen atom in nanometers?5. The distance between the nuclei of two covalently bonded iodine atoms is 276 pm. What is the diameter of 1 iodine atom in pm?64 pm.0710 nm276 pm
8 B. Group/Family Trends1. Size increases as you move down a column.-Why?electrons are added to energy levels farther away from the nucleus.-How can electrons get into energy levels away from the nucleus?electrons are shielded from the positive nuclear charge by 1s electrons…2s electrons…2p electrons… and so forth.2. Shielding demo
10 In Class Assignment1. Place the following atoms in order from smallest to largest in terms of their atomic radius.Br, I, Be, He, Rn2. Why is a sodium atom smaller than a potassium atom?He < Be < Br < I < RnBecause potassium has more electrons and these electrons fillenergy levels that are farther away from the nucleus of asodium atom.
11 C. Periodic Trends1. Atomic radii decreases as you move from left to right.Why?electrons are added to the same principle energy level. Nuclear charge pulls electrons in closer to the nucleus.
14 In Class Assignment1. How would you describe the atomic radius of a period 2 alkaline earth metal compared to a period 4 alkaline earth metal?2. How would you describe the atomic radius of a period 3 alkali metal and a period 3 halogen?The atomic radius of the period 2 a.e.m.would be smaller than the period 4 a.e.m.The atomic radius of a period 3 a.m. would belarger than a period 3 halogen due to nuclearcharge.
15 II. Trends in Ionization Energy A. Def – the amount of energy required to overcome the attraction of the nuclear charge and remove an electron from an atom.Energy1+e-e-e-e-e-e-e-e-e-NaNae-e-e-e-e-e-e-e-e-e-e-e-
16 1. 1st Ionization Energy-removing the 1st electron2. 2nd Ionization Energy-removing an electron from a 1+ ion.3. 3rd…4th…5th… and so on**Note table 6.1
19 B. Group Trends1. Ionization energy decreases as you move down a group.Why?The farther electrons are from the nuclear charge, the easier they are removed.C. Period Trends1. Ionization energy increases as you move from left to right.The nuclear charge increases, but the electron shield does not.**Remember noble gases do not want to give up electrons**
21 III. Trends in Ionic Size A. Ion Review1. metals low ionization energy2. non-metals high ionization energy**How does losing/gaining an electron affect the size of an ion???**B. Cations and Anions1. Cations = always smaller than their neutral atomsWhy?loss of an electron causes the nuclear charge to increase. Thus the remaining electrons are pulled in farther.
25 1. Ionic size increases as you move down a C. Group Trends1. Ionic size increases as you move down agroup on the periodic table.Anions decreaseCations decreaseIncreasesD. Periodic Trends1. Ionic size decreases from left to right for both cation and anions
26 1. How does the ionic radius of sodium compare to that of cesium? Cesium is larger2. How does the ionic radius of boron compare to that of fluorine?Fluorine is larger
27 IV. ElectronegatvityA. Def – the tendency for an atom to attract electrons from another atom.1. similar to magnetism2. Electronegativity is a relative value based on ionization energy.3. Noble Gases are not included…Why???-they don’t form compoundsB. Electronegativity Trends1. E-negativity decreases as you move down a column.2. E-negativity increases as you move across a period.-Fluorine = most electronegative element-Cesium = least electronegative element
28 3. Metals = low e-negativity Non-metals = high e-negativity E-negativity = tug of warFluorine or Cesium?Calcium or Sulfur?Oxygen or Magnesium?Oxygen or Nitrogen?4. E-negativity values help predict types of bonds.FluorineSulfurOxygenOxygen