Transcript Unit 4: Electron Configuration, Periodic Trends and

Do Now:
 Take
out completed homework #1
 Take out Atoms Book
Review before the quiz
_____1) Bohr’s model of the atom says
that electrons
a) are mixed in evenly with positive charge
b) are found orbiting a positively-charged
nucleus
c) are found orbiting a positively-charged
nucleus in energy levels (shells)
d) are found in regions of probability
around the nucleus called orbitals
Review Before the Quiz
_____5) Dalton’s model of the atom
states that atoms
e) have positive particles called protons
and negative particles called electrons
f) have a positively-charged nucleus
g) have a positively-charged nucleus with
electrons in energy levels (shells)
h) are hard solid indivisible spheres
Review Before the Quiz

One model of the atom states that
atoms are tiny particles composed of a
uniform mixture of positive and
negative charges. Scientists conducted
an experiment where alpha particles
were aimed at a thin layer of gold
atoms. Most of the alpha particles
passed directly through the gold atoms.
A few alpha particles were deflected
from their straight-line paths. (This
question was taken directly from a
Regents Exam).
Review before the quiz

Most of the alpha particles passed
directly through the gold atoms
undisturbed. What does this evidence
suggest about the structure of gold
atoms?

Atoms are mostly empty space
Review before the quiz
A few of the alpha particles were
deflected. What does this evidence
suggest about the structure of the gold
atoms?
 The nucleus must be positive since it
deflects positively charged alpha
particles

Quiz-E-Poo time
12.5 minutes
 Can use your notes/atom book. Turn
ALL OF IT IN when you are done
 Atom Book
 Homework
 Quiz

Where are electrons found in the
electron cloud?
Bohr was the first to propose that the
electrons were located in energy levels
 A lower case “n” is used to denote
these principle energy levels (also
called principle quantum numbers).
 The level closest to the nucleus is
labeled n = 1. The next level is labeled
n = 2 and so forth.

Where are electrons found in the
electron cloud?
Each principle energy level had a certain
energy value associated with the level.
 The closer the level was to the nucleus,
the lower the energy of the level.

Where are electrons found in the
electron cloud?
The farther away from the nucleus, the
higher the energy of that level.
 As long as the electrons were in these
levels, the electrons do not give off
energy.

Number the principle Energy levels
5
4
3
2
1
Sidebar: How did he figure that
out?
Excited Electrons
 Viewed what the spectrum produced
was:
 Demo:

2. Electron Configuration and the
Periodic Table
Each principle energy level can only
hold so many electrons before the level
is full.
 A quick and easy way to determine the
maximum number of electrons (max e-)
that a principle energy level can hold is
given by the following:

max e- = 2 n2.
max e- = 2 n2.
 First square the principle energy level
number (n) then multiply by 2

2n2 Trick
Principle Energy
Level (n)
1
2
3
4
5
6
Maximum
Electrons
2
8
18
32
50
72
Electron Configuration
Electrons are arranged around the
nucleus by filling up the first principle
energy level (n=1), then the second
energy level, etc.
 This is the electron configuration given
on your periodic table.

Electron Configuration
The number of electrons
are listed for each level with
a dash between levels:
 for oxygen (O) which has a
total of 8 electrons, the
configuration is 2–6

Electron Configuration
2
electrons are located in
the first principle energy
level
 6 electrons are located in
the second principle
energy level.
Look up the electron config. on
the PT for the element given &
fill in the chart.
Element
Ca
Na
F
B
n=1
2
n=2
8
n=3
8
2
2
2
8
7
3
1
n=4
2
Look up the electron config. on
the PT for the element given &
fill in the chart.
Element
Al
C
H
n=1
n=2
n=3
n=4
Side Bar: Look up # 72 Hf

What does the ** mean?
So the electron configuration of Hf is…..
 2-8-18-32-10-2
 What is the electron configuration of gold (Au)
# 79?
 2-8-18-32-18-1

Completely Filled vs. Occupied Principle
Energy Levels
 Is
this room occupied?
 Are
all the seats completely filled?
Completely Filled vs. Occupied Principle
Energy Levels
 Occupied
means that
there is at least one
electron in the Principle
Energy Levels (PEL)
 Li: 2 – 1 has 2 occupied
PELs
Completely Filled vs. Occupied Principle
Energy Levels
 Completely Filled
means that each level
has its maximum
number of electrons
which can be
determined by the 2n2
rule.
 n =1 then 2(1)2 =2
& n = 2 then 2(2)2=8
 Li: 2 – 1 has only 1
Completely Filled PEL
To help you review the 2n2 rule
complete the following chart
PEL 1
(n)
Max 2
e-
2
3
8
18
4
5
32 50
6
72
7
98
In the chart:
Copy the electron configuration from the
Periodic Table
 Determine the number of Occupied
Principle Energy Levels (PEL)
 Determine the number of Completely
Filled Principle Energy Levels

Max e-: 2-8-18-32-50-72-98
Elemen Electron Conf.
t
C
2-4
#
ocup
p
#
compl
filled
2
1
Max e-: 2-8-18-32-50-72-98
Elemen Electron Conf.
t
Na
O
Cl
#
ocup
p
#
compl
filled
2-8-1
3
2
2-6
2
1
2-8-7
3
2
Max e-: 2-8-18-32-50-72-98
Elemen Electron Conf.
t
He
F
Ne
#
ocup
p
2
1
2-7
2-8
2
2
#
compl
filled
1
1
2
Max e-: 2-8-18-32-50-72-98
Elemen Electron Conf.
t
Si
Zn
Au
#
ocup
p
#
compl
filled
2-8-4
3
2
2-8-18-2
4
3
2-8-18-32-18-1 6
4
3. Drawing Bohr Diagrams of
Atoms:
 1) A circle
is used for the nucleus- the
# protons (# p or +) and the # of
neutrons (#n) are placed in the circle.
 2) A ring is drawn around the nucleus
for each energy level.
 3) The electrons for each energy level
are placed in pairs symmetrically
around the nucleus
For Fluorine (F)
atomic # = _________
atomic mass = ______
electron configuration:
__________________
_
#p=
______________
#n
=_______________
For Aluminum (Al)
atomic # = _________
atomic mass = ______
electron configuration:
__________________
#p=
______________
#n
=_______________
Going Backwards:
Determining the identity
of an element from the
Bohr diagram:
# p = _____________
 # n =______________
 atomic # =
_____________
 atomic mass = # p + #
n=
 ________________
 electron configuration:
 ___________________
____
 Isotopic Notation:

Going Backwards:
Determining the identity
of an element from the
Bohr diagram:
# p = _____________
 # n =______________
 atomic # =
_____________
 atomic mass = # p + #
n=
 ________________
 electron configuration:
 ___________________
____
 Isotopic Notation:

To review:






To draw a Bohr Model:
Look up the atomic #, atomic mass & the
electron configuration
Determine the # of neutrons (atomic massatomic #)
Draw nucleus & write the # p & #n in nucleus
Draw rings around the nucleus equal to the # of
PEL in atom (# of numbers in electron
configuration)
Place electrons for each level symmetrically in
the rings in pairs
Going Backwards writing Isotopic
Notation:
# of protons = atomic number so look up the
atomic # to get symbol
 Add the # of protons and neutrons to get the
atomic mass (mass #)


Atomic mass is the top number
20
Ne
10

Atomic # is the bottom number
Now it is your turn!
Complete the Bohr
Model worksheet.
 When done, show
me and turn in.
 If not done, it
becomes
homework along
with homework #2.
