Chapter 14 Lesson 2

Honors ChemistryChapter 5 Lesson 3Periodic TrendsThe Big IdeaNuclear Charge the effect protons of an atom have on its size, shape and characteristics.NC +NC +Periodic TableI. Trends in Atomic SizeA. Atomic Radius1. Def one half of the distance between the nuclei of two like atoms in a diatomic molecule.

-radius = from center to outer edge2. Measured in a. Picometers (10-12 m)b. angstroms () (10-10 m)c. Nanometers (10-9)

3. The distance between the nuclei of two covalently bonded fluorine 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? 64.0 pm.0710 nm276 pm

B. Group/Family Trends1. Size increases as you move down a column.-Why? electrons are added to energy levels farther away from the nucleus.C. Periodic Trends1. size decreases as you move left to right in a period-Why?electrons are shielded from the positive nuclear charge by 1s electrons2s electrons2p electrons and so forth. 2. Shielding demoIn Class Assignment1. Place the following atoms in order from smallest to largest in terms of their atomic radius.Br, I, Be, He, Rn

2. Why is a sodium atom smaller than a potassium atom?

He < Be < Br < I < Rn Because potassium has more electrons and these electrons fill energy levels that are farther away from the nucleus of a sodium atom.

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 nuclear charge.II. Trends in Ionization EnergyA. Def the amount of energy required to overcome the attraction of the nuclear charge and remove an electron from an atom.Energy

Nae-e-e-e-e-e-e-e-e-e-e-Nae-e-e-e-e-e-e-e-e-e-1+

1. 1st Ionization Energy-removing the 1st electron2. 2nd Ionization Energy-removing an electron from a 1+ ion.3. 3rd4th5th and so on

**Note table in book

Periodic TableI.E. +I.E. -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. Why?The nuclear charge increases, but the electron shield does not.**Remember noble gases do not want to give up electrons**III. Trends in Ionic Size**How does losing/gaining an electron affect the size of an ion???**A. Ionic Size1. metals form cation low ionization energya. Smaller than their neutral atomWhy?loss of an electron causes the nuclear charge to increase. Thus the remaining electrons are pulled in farther.

e-e-e-2. non-metals form anions high ionization energya. larger than their neutral atom. Why? The increase of another electron causes the nuclear charge to decrease. Thus the size of the ion increases.

Ionic Size -Ionic Size +IV. Electron AffinityA. Def the energy change that occurs when it gains an extra electron.1. Attraction for extra electron(s)2. Most have negative affinities pg. 1823. loose energy when an electron is addedB. Trends1. Is there one?2. Pg. 182a) non-metals more negative b) metals less negative3. Noble Gases positive affinity*related to the number of es needed to octetV. ElectronegativityA. Def the tendency for an atom to attract electrons from another atom.1. similar to magnetism2. Scale on page 1843. Noble Gases are not includedWhy???-they dont 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-Francium = least electronegative element3. Metals = low e-negativityNon-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

Electronegativity Chart

4.0 strongest0.7 weakest