Catalyst – February 13, 2012 Monday Mystery Element! 1. Easily magnetized 2. Important for human nutrition by preventing anemia 3. Can become radioactive and emit gamma rays (can treat cancer)

Catalyst – February 13, 2012 Monday Mystery Element! 1. Easily magnetized (like your heart is for Chemistry) 2. Important for human nutrition by preventing anemia 3. Can become radioactive and emit gamma rays (can treat cancer) COBALT!

Today’s Agenda  Catalyst  Review Quiz 2.1  Notes: Bohr Models and Periodic Trends  Work Time  Exit Question HOMEWORK: ATOMIC TRENDS WORKSHEET

Today’s Objectives  SWBAT draw Bohr Models for the first 20 elements like pros!  SWBAT describe the periodic trends for valence electrons, atomic radius, and electronegativity.

Quiz 2.1 Grade Averages 2 nd Period: 72.5% (D)  3 rd Period: 71.6% (D)  5 th Period: 64.9% (F)  FYI: Ms. Stroh added 5 points to the grade you see on your paper.

Quiz 2.1 Champs  1 st Place (102!): Ryan Craigie (3 rd )  2 nd Place (97): Josh Hayes (3 rd ), Destiny Rhea (3 rd )  3 rd Place: Jaymie Mayberry (3 rd )

NOTES: BOHR MODELS

Bohr Models of Atoms  Key Point #1: A Bohr model depicts an atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus 16 p+ 16 n o Sulfur: 16 protons 16 neutrons 16 electrons

Energy Levels  Key Point #2: Energy levels (or shells) are paths around the nucleus where electrons travel  Energy levels are also known as orbits  Energy increases as you move further from the nucleus

Valence Electrons  Key Point #3: Valence electrons (ve-) are electrons in the outermost energy level  They are the furthest from the nucleus  An atom could have 1 ve-, 2 ve-, 3 ve-, etc.

Steps to Making a Bohr Model 1. Determine the number protons, neutrons, and electrons in the atom 2. Draw the nucleus (circle) with # p+ and # n o inside 3. Draw the first energy level (circle around nucleus) and draw up to 2 dots (electrons) 4. If needed, draw second energy level (second circle) and draw up to 8 dots (electrons) 5. If needed, draw third energy level (third circle) and draw up to 8 dots (electrons) 6. If needed, draw fourth energy level (fourth circle) and draw up to 18 dots (electrons)

CHECK OVER YOUR BOHR MODELS DO YOU HAVE ANY QUESTIONS???

NOTES SECTION: PERIODIC TRENDS!!! VALENCE ELECTRONS ATOMIC RADIUS ELECTRONEGATIVITY

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved..  Although the weather changes from day to day, the weather you experience is related to your location on the globe. CHEMISTRY & YOU How are trends in the weather similar to trends in the properties of elements?

Periodic Trends  Key Point #4: There are trends/patterns on the periodic table that help us both compare and contrast elements.

Note-Taking Strategy  Make a T-chart in your notes – like this…. Vocab Word Periodic Trend

Vocab Words (Left) 1. Valence electrons: electrons in the outermost (or outside/biggest) energy level 2. Atomic radius: how big an atom is, also known as atomic size 3. Electronegativity: the ability of an atom to attract electrons to itself in a chemical bond; how much an atom wants electrons

Electronegativity Values for Selected Elements in Paulings H 2.1 Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 K 0.8 Ca 1.0 Ga 1.6 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Rb 0.8 Sr 1.0 In 1.7 Sn 1.8 Sb 1.9 Te 2.1 I 2.5 Cs 0.7 Ba 0.9 Tl 1.8 Pb 1.9 Bi 1.9

VALENCE ELECTRONS TREND

Let’s look at Bohr Models… 

Valence Electrons Write on your PT

TREND: Valence Electrons  # of valence electrons increases from 1-8 as you go left to right

Using Graphs to Understand the Relationship Between Atomic Radius and Electronegativity

GROUP 1 H + Alkali Metals

PERIOD 1 Li - Ne

ATOMIC RADIUS TREND

Rank Small to Large: Cs, Ga, P, Rn

ELECTRONEGATIVITY TREND

Rank Small to Large: Mg, Sr, Be, Ra

Why is this relationship true? vs. LARGE EN = SMALL AR LARGE AR = SMALL EN

Work Time  Work on worksheet from Ms. Stroh

Exit Question 1. Draw the Bohr model for Carbon (C). 2. Which element has the largest electronegativity: Ag, Cu, Hg, or Zn? HOMEWORK: ATOMIC TRENDS WORKSHEET