Transcript Bohr Models, Periodic Trends - stroh

Catalyst – February 13, 2012
1.
2.
3.
Monday Mystery Element!
Easily magnetized
Important for human
nutrition by preventing
anemia
Can become radioactive
and emit gamma rays (can
treat cancer)
Catalyst – February 13, 2012
COBALT!
1.
2.
3.
Monday Mystery Element!
Easily magnetized (like
your heart is for Chemistry)
Important for human
nutrition by preventing
anemia
Can become radioactive
and emit gamma rays (can
treat cancer)
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
Period: 72.5% (D) 
rd
3 Period: 71.6% (D) 
th
5 Period: 64.9% (F) 
nd
2
FYI: Ms. Stroh added 5 points to the
grade you see on your paper.
Quiz 2.1 Champs
1st Place (102!): Ryan Craigie (3rd)
 2nd Place (97): Josh Hayes (3rd),
Destiny Rhea (3rd)
 3rd Place: Jaymie Mayberry (3rd)

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 no
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.
2.
3.
4.
5.
6.
Determine the number protons, neutrons, and
electrons in the atom
Draw the nucleus (circle) with # p+ and # no inside
Draw the first energy level (circle around nucleus)
and draw up to 2 dots (electrons)
If needed, draw second energy level (second
circle) and draw up to 8 dots (electrons)
If needed, draw third energy level (third circle)
and draw up to 8 dots (electrons)
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
CHEMISTRY
& YOU
How are trends in the weather similar to
trends in the properties of elements?

Although the weather
changes from day to
day, the weather you
experience is related
to your location on the
globe.
Copyright © Pearson Education,
Inc., or its affiliates. All Rights
Reserved.
.
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.
2.
3.
Valence electrons: electrons in the
outermost (or outside/biggest) energy level
Atomic radius: how big an atom is, also
known as atomic size
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…
http://www.chemicalelements.com/show/electronconfig.html

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
300
250
200
150
100
50
0
0
1
2
3
4
5
6
7
Element
2.5
2
Electronegativity
Atomic Radius (picometer)
350
1.5
1
0.5
0
0
1
2
3
4
Element
5
6
7
8
PERIOD 1
Li - Ne
140
120
100
80
60
40
20
0
0
2
4
6
8
10
Element
4.5
Electronegativity
Atomic Radius (picometer)
160
4
3.5
3
2.5
2
1.5
1
0.5
0
0
2
4
Element
6
8
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.
2.
Draw the Bohr model for Carbon (C).
Which element has the largest
electronegativity: Ag, Cu, Hg, or Zn?
HOMEWORK:
ATOMIC TRENDS WORKSHEET