What is a model?

Conceptual models are used to help us know, understand, or simulate the subject matter they represent. They are not necessarily what the subject ‘looks like’.

Today we will make room-sized models of the atom

• Tape circles on the floor represent ‘shells’ or ‘energy levels’ (these terms are synonymous)

• Red circles represent protons– Placed in nucleus

• Grey circles represent neutrons– Placed in nucleus

• Students represent electrons– Valence electrons– Electrons (“inner” or “core”)

How this works:

• Form groups of 3• You need a periodic table in your hands (don’t lose it!)• Each slide presents a challenge• Your group must:– Be ready to tell other students (or yourself!) where to go to

complete the atom– Spot mistakes and be ready to correct them– Look for patterns and rules– Answer any questions about the model: look for “_____”

Challenge #1 Build this atom:

Hydrogen-11 proton

1 electron (1)0 neutrons

What is the mass number?___What is the charge?___

Challenge #1 Build this atom:

Hydrogen-11 proton

1 electron (1)0 neutrons

What is the mass number?What is the charge?

10

Lewis dot structure for H (more details on this later)

Helium-22 protons

2 electrons (2)2 neutrons

 

What is the mass number?___ What is the charge?___

How many energy levels are occupied?___

Helium-22 protons

2 electrons (2)2 neutrons

 

What is the mass number? What is the charge?

How many energy levels are occupied?

40 1

Lewis dot structure for helium (2 valence electrons)

Lithium-73 protons

3 electrons (2,1)4 neutrons

What is the atomic number?___What is the mass number?___

How many shells are occupied?___How many electrons in the outermost

shell?___

Lithium-73 protons

3 electrons (2,1)4 neutrons

What is the atomic number?What is the mass number?

How many shells are occupied?How many electrons in the outermost shell?

3721

Here is the Lewis dot structure for lithium:

Beryllium-94 protons

4 electrons (2, 2)_____ neutrons

 

Determine the number of neutrons in this isotope of beryllium:__ What is the charge?__

How many electrons in the first energy level?__How many electrons in the second energy level?__

Beryllium-94 protons

4 electrons (2, 2)_____ neutrons

 

Determine the number of neutrons in this isotope of beryllium: What is the charge?

How many electrons in the first energy level?How many electrons in the second energy level?

5022

Boron-11____ protons

_____ electrons (2, 3)6 neutrons

How many protons are in the nucleus?___What is the atomic number?___

What is the mass number?___How many total electrons?___

Build it….then answer these questions:

Boron-11____ protons

_____ electrons (2, 3)6 neutrons

How many protons are in the nucleus?What is the atomic number?

What is the mass number?How many total electrons?

55115

Build it….then answer these questions:

Boron-10____ protons

_____ electrons (2, 3)5 neutrons

How many protons are in the nucleus?___What is the atomic number?___

What is the mass number?___How many total electrons?___

Build it….then answer these questions:

How is Boron-10 different from Boron-11?___

Boron-10____ protons

_____ electrons (2, 3)6 neutrons

How many protons are in the nucleus?What is the atomic number?

What is the mass number?How many total electrons?

55105

Build it….then answer these questions:

How is Boron-10 different from Boron-11? # of neutrons, mass

Isotopes are only different by the number of neutrons they contain. Their Lewis dot structures are totally identical!

Boron-10 Boron-11

Fluorine- 19____ protons_____electrons (__, __)_____neutrons

Fill in the blanks.

For all examples so far, what is the maximum number of electrons in the first shell?___

How many electrons are in the second shell of this atom??___

What will the Lewis dot structure look like?___

Fluorine- 19____ protons_____electrons (2, 7)_____neutrons

Fill in the blanks.

For all examples so far, what is the maximum number of electrons in the first shell?

How many electrons are in the second shell of this atom??

What will the Lewis dot structure look like?

9910

27

7 dots

Neon-20____ protons_____electrons (__, __)_____neutrons

Fill in the blanks.

For all examples so far, the charge has been zero. Why?___

How many electrons are in the second shell?___ What will the Lewis dot structure look like?___

Neon-20____ protons_____electrons (2, 8)_____neutrons

Fill in the blanks.

For all examples so far, the charge has been zero. Why?

How many electrons are in the second shell? What will the Lewis dot structure look like?

101010

Protons = Electrons

88 dots

What happens after Ne? Pattern?

Sodium-23____ protons____ electrons (_, _, _)____ neutrons

How many valence electrons?___Where does the single valence electron go?___What is the maximum number of electrons that can go into the second shell?___

What will the Lewis dot structure look like?___

Sodium-23____ protons____ electrons (2, 8, 1)12 neutrons

How many valence electrons?Where does the single valence electron go?What is the maximum number of electrons that can go into the second shell?

13rd shell

8 elec.

1111

What will the Lewis dot structure look like?

Silicon-28__ protons__ electrons (_, __, __)14 neutrons

True or false: Before any electrons go into the 3rd shell, the first and second shells must be full______

Silicon-28__ protons__ electrons (_, __, __)14 neutrons

2 8 4

True or false: Before any electrons go into the 3rd shell, the first and second shells must be full______

Can you draw the Lewis dot structure?

Can you draw the Lewis dot structure?

7Li+3 protons

___ electrons (__)4 neutrons

What is the atomic number?___What is the mass number?___

How many shells are occupied?___How many electrons in the outermost shell?

___

7Li+3 protons

___ electrons (2)4 neutrons

What is the atomic number?What is the mass number?

How many shells are occupied?How many electrons in the outermost shell?

3712

If time….

Additional challengesMg2+

Cl-

Key Points• Neutrons only add mass to an atom• Electrons can be found in ‘shells’ or ‘energy levels’

that surround the nucleus • Each shell is distinct (electrons are in shell 1 or 2,

not 1.5)• First shell: 2 electrons• Second shell: 8 electrons• Third shell: 8 electrons• Electrons always inhabit lowest shells first• Lewis dot structures only show electrons in

outermost shell (‘valence shell’)• Ions are formed when atoms gain or lose electrons

Time for practice:Atomic Symbols and Isotopes WS