do now: take out completed homework #1 take out atoms book

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

UNIT 4: ELECTRON CONFIGURATION,

PERIODIC TRENDS AND HISTORY OF THE ATOM

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

1

2

3

45

Sidebar: How did he figure that out? Excited Electrons Viewed what the spectrum produced

was: Demo:

hydrogen-atom_en.jar

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)

Maximum Electrons

123456

28

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 n = 1 n = 2 n = 3 n = 4

Ca 2 8 8 2NaFB

2 8 12 72 3

Look up the electron config. on the PT for the element given & fill in the chart. Element n = 1 n = 2 n = 3 n = 4

AlCH

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 (n)

1 2 3 4 5 6 7

Max e- 2 8 18 32 50 72 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-: 2-8-18-32-50-72-98Element

Electron Conf. # ocupp

# compl filled

C 2 12-4

Max e-: 2-8-18-32-50-72-98Element

Electron Conf. # ocupp

# compl filled

NaOCl

2-8-1

2-6

2-8-7

3 2

2 1

3 2

Max e-: 2-8-18-32-50-72-98Element

Electron Conf. # ocupp

# compl filled

HeFNe

2

2-72-8

1 12 12 2

Max e-: 2-8-18-32-50-72-98Element

Electron Conf. # ocupp

# compl filled

SiZnAu

2-8-4

2-8-18-2

2-8-18-32-18-1

3 2

4 3

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 mass-

atomic #) 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

10Ne20

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.