Chemical Models of Elements Bundle 2: Periodic Table & Bonding NOTE: You need to show them how to draw a Lewis Dot Diagram, AND how to use the diagram to draw the structure with only lines for the bonding sites. Emphasize that the BONDING SITES must be the same no matter the configuration of the electrons around the symbol.

Drawing Bohr Models

Bohr Models Bohr models are used to predict reactivity in elements. Reactivity refers to how likely an element is to form a compound with another element. When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.

Drawing Bohr Models Draw the nucleus. Write the number of neutrons and the number of protons in the nucleus. Draw the first energy level. Draw the electrons in the energy levels according to the rules below. Make sure you draw the electrons in pairs. Keep track of how many electrons are put in each level and the number of electrons left to use.

Rules for Energy Levels Level 1 (closest to the nucleus) can hold a maximum of 2e. Level 2 can hold a max of 8e. Level 3 can hold a max of 18e. Level 4 can hold a max of 32e. You must fill one level before going on to draw the next level!

How to determine the # of Neutrons The Atomic Mass of an element from the PT is an AVERAGE Mass of all of the elements isotopes. (Remember Hydrogen) For a NEUTRAL atom, round the Atomic Mass to the nearest whole number. This will be the ESTIMATED number of neutrons in the nucleus of the atom. To know the EXACT number of neutrons, you must be given the EXACT Atomic Mass.

Guided Practice In order to draw Bohr models of these elements, you must first determine the number of protons, neutrons, and electrons. Once you have found this information, follow the directions to draw your model. 6 6 6 6 C Carbon 12.011 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 2 4

Guided Practice 16 S Sulfur 32.066 16 16 16 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 3 6

Guided Practice Protons: _____ Neutrons: _____ Electrons: ______ 3 Li Lithium 6.941 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 3 4 3 2 1

Guided Practice 10 10 10 10 Ne Neon 20.180 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 2 8

Guided Practice 15 16 15 15 P Phosphorus 30.974 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 3 5

Guided Practice 11 12 11 11 Na Sodium 22.990 Protons: _____ Neutrons: _____ Electrons: ______ How many energy shells will this have? ____ How many valence (outer) electrons does this element have? ____ Bohr Model: 3 1

Here’s a short video on how to draw Lewis Dot Structures. https://www.youtube.com/watch?v=HCOI4-AYA1U

Write down what you observe.

Critical Write Write in your notebook the elements used in the demonstrations in the video and answer the following questions. What did you notice about each element when it was mixed with water? Why do you think this occurred?

Video Wrap Up Discussion – What did you notice? Reactivity refers to how likely an element is to form a compound with another element. Most Reactive Non-Metal Group? Group 17 (Halogens) Most Reactive Metal Group? Group 1 (Alkali Metals)

Lewis Dot Structures Lewis Dot Structure Illustrates the number of VALENCE Electrons Helps us determine how compounds are formed / how elements bond Electrons are drawn in pairs around the element. A Lone Electron is called a BONDING SITE.

Drawing Lewis Dot Structure Write the SYMBOL of the element. How many valence electrons does the element have? (What group is it in?) Start at 12:00 with your first dot Add dots at 3:00, 6:00, and 9:00 moving clockwise until you reach the correct number of valence electrons. You need one dot at each location before you start adding your second round of dots **These rules are guidelines, not exact. Some conventions go counterclockwise, others draw the structure exactly the same for all group elements. The structure is fluid, it can be rearranged to set up the element for bonding.

Practice Chemical Symbol: ____ Atomic Number: _____ Atomic Mass: ____ Draw the Lewis Dot Diagram for Phosphorus Chemical Symbol: ____ Atomic Number: _____ Atomic Mass: ____ Protons: ____ Neutrons: _____ Electrons: _____ # of Valence Electrons: _______ P 15 30.974 15 16 15 5

Practice Chemical Symbol: ____ Atomic Number: _____ Atomic Mass: ____ Draw the Lewis Dot Diagram for Fluorine Chemical Symbol: ____ Atomic Number: _____ Atomic Mass: ____ Protons: ____ Neutrons: _____ Electrons: _____ # of Valence Electrons: _______ F 9 18.998 9 10 9 7

Connection to Bonding Lewis Dot Structures help in Bonding two or more elements together to form compounds. You can see the bonds in Lewis Dot form, or using bonding structures with lines as shown in the examples below. Each line represents 2 electrons.