Launch: 9/23   Grab your binder and immediately take a seat

  Place Quiz Corrections and Textbook HW on desk

  With your partner, go over the answers to the homework

What are the periodic trends?

Mr. Heffner 9/23/09

Review

Review

What are trends?   Trend: a general rule that is followed

  New Boyz are trendy, and everyone is following their style

  On the periodic table there are 5 trends   Atomic number

  Atomic mass

  Atomic radius

I. Atomic Number A.  What is atomic number?

1.  The number of protons in an atom

B.  What is the trend? 1.  Atomic number increases across a period (LR)

2.  Atomic number increases down a group (TopBottom)

I. Atomic Number Increases

Incr

ease

s

II. Atomic Mass A.  What is atomic mass?

1.  The number of protons and neutrons in an atom

B.  What is the trend? 1.  Atomic mass increases across a period (LR)

2.  Atomic mass increases down a group (TopBottom)

II. Atomic Mass In

crea

ses

Increases

III. Atomic Radius A.  What is atomic radius?

1.  The distance from the nucleus to the valence ring

2.  The size of an atom

0

0

0

0

III. Atomic Radius B.  What is the trend?

1.  Atomic radius decreases across a period (LR) i.  As the number of protons increases, attraction with the

electrons increases

ii.  Electrons are pulled towards the nucleus making the atom smaller

Chihuahua Story   I am a dog walker

  Everyday I walk 8 Chihuahuas

  The stronger I am, the closer I can pull them towards me

III. Atomic Radius B.  What is the trend?

2.  Atomic radius increases down a group (TopBottom) i.  As the number of electrons increases, need more rings

ii.  More rings take up more space

iii. Shielding: electrons repel each other

Chihuahua Story   I am a dog walker

  Instead of 8 Chihuahuas, I now have 9

  I can’t fit any more around me, need a longer leash

III. Atomic Radius In

crea

ses

Decreases

Summary

Practice Questions 1.  What is atomic radius?

2.  Describe the trend for atomic radius.

3.  Name three elements that have a larger atomic radius than C?

4.  Name three elements that have a smaller atomic radius than C?

5.  Which has a larger radius, P or S; F or Cl; Li or Cs; Pt or Ni; Fr or F; Se or O?

6.  Which element in group 14 has the largest atomic radius? The smallest?

Homework   Textbook Problems:

  Pg. 141 Section Review: #4, 6, 8   Pg. 151 Chapter Review: # 31

  Finish Practice Problems

  Start reviewing for Monday’s Unit #2 Exam!

  lpschem.wordpress.com

Exit Slip 1. Atomic radius is the

a. number of protons in an atom. b. number of protons and neutrons in an atom.

c. number of atoms found in a circle. d. size of an atom.

2. Atomic radii __________ as you go from fluorine (F) to iodine (I) on the periodic table.

a. increase b. decrease

c. stay the same d. none of the above

Exit Slip 3. In general, how does atomic radius vary

throughout the periodic table? a. it decreases across a period from left to right, and

decreases down a group from top to bottom b. it decreases across a period from left to right, and

increases down a group from top to bottom c. it decreases across a period from right to left, and

increases down a group from top to bottom d. it is fixed and does not change as you move across

the periodic table

Exit Slip 4. Which of the following atoms has a larger atomic

radius than potassium (K)? a. sodium (Na) b. magnesium (Mg) c. calcium (Ca)

d. rubidium (Rb)

5. Which of the following atoms has the largest atomic radius? a. oxygen (O) b. phosphorus (P)

c. sulfur (S) d. chlorine (Cl)