Understanding Elements Part 1: How to Draw Bohr Diagrams of Atoms

Atom Diagrams Why do we have to do this??? Why does it even “matter” ? Atoms make up all matter. And since we are matter, we are made of atoms. Our very lives depend on atoms. Where we would be without oxygen? Where would we be without water? These are made of atoms. Drawing atom diagrams helps us visualize what atoms may actually look like (since they’re too small to see), and later on, these atom diagrams will help us understand why elements on the periodic table have certain physical and chemical properties and why they are placed where they are on the periodic table.

Atom Diagrams (cont.) Atom diagrams show the location of the different parts of the atom, but they put the spotlight on the electrons. Remember that electrons are NOT in the nucleus. They orbit the nucleus similar to how the planets orbit the sun. Although electrons are tiny and don’t contribute to the mass (weight) of the atom, electrons are INCREDIBLY IMPORTANT.

You need your: Vocab. Sheets Worksheet Part C: Electron Configuration.

Bohr Diagrams of atoms use “rings” to show the arrangement of electrons. We call these rings “energy levels”, “electron shells”, or “orbitals”. Let’s fill in #28 on your vocab. sheet.

The periodic table has rows and columns. Elements are in certain rows and columns for a reason. 29. Periods- the horizontal rows on the periodic table; *tells the number of energy levels (orbitals) each element on the row has. *There are only 7 periods (rows) so no more than 7 orbitals for any atom. Elements in the 1 st period (row) have one energy level. Elements in the 2 nd period (row) have two energy levels, and so on

In a Bohr Diagram… On the worksheet: How many electrons can each energy level (orbital/electron shell) hold? 1 st level can hold 2 electrons. 2 nd level can hold 8 electrons. 3 rd level can hold 8 electrons. 27. Electrons on the outermost shell (level) of an atom are known as valence electrons. A.D. Determine how reactive an element is.

Remember that the PERIOD (row) an element is on tells you how many energy levels it has.

How to Draw Bohr Diagrams of Atoms 1)Find your element on the periodic table. 2)Determine the number of electrons – it is the same as the atomic number (number of protons…Protons=electrons). This is how many electrons you will draw.

To draw Bohr Diagrams… 3) Write the element symbol. This represents the nucleus. Carbon is in the 2 nd period (row), so it has two energy levels, or shells. 4) Draw the shells around the nucleus. C

To draw Bohr Diagrams… 5) Add the electrons. Carbon has 6 electrons. The first shell can only hold 2 electrons. C

To draw Bohr Diagrams… Since you have 2 electrons already drawn, you need to add 4 more. These go in the 2 nd shell. Add one at a time - starting on the right side and going counter clock- wise. C

To draw Bohr Diagrams… Check your work: You should have 6 total electrons for Carbon. The 1st shell should have 2 electrons. The 2 nd shell should have 4 electrons. Is the 2 nd shell full? C

Let’s look at another example of how to draw a Bohr diagram. This time, let’s see how we would diagram oxygen.

To draw Bohr Diagrams… 1. Draw the symbol for oxygen. 2. Find oxygen on the p.t. Oxygen is in Period (row) 2 on the periodic table. So an oxygen atom has 2 energy levels/electron shells. 3. Oxygen is atomic number 8, so we know it has 8 protons, thus 8 electrons. Draw the electrons for the 1st energy level. It can only hold 2 electrons. O

To draw Bohr Diagrams… Since you have 2 electrons already drawn, you need to add 6 more. These go in the 2 nd shell. Add one at a time - starting on the right side and going counter clock- wise. When you circle back around, start pairing up the electrons. O

To draw Bohr Diagrams… Check your work: You should have 8 total electrons for Oxygen. The 1st shell should have 2 electrons. The 2 nd shell should have 6 electrons. Is the 2 nd shell full? O

The goal of every atom is to have a full outermost shell. Atoms will gain or lose electrons in order to have a full outermost shell. This does not change what element it is. Look at the bottom of your worksheet.

The Octet Rule Atoms like to have 8 valence electrons. Atoms with 8 valence electrons (a full outer shell) are more stable. Even atoms need stability in their lives!!!

To be stable: Atoms with 1, 2 or 3 valence electrons are more likely to lose (give up) their outer electrons. Atoms with 6 or 7 valence electrons are more likely to gain electrons to fill their outer shell. Atoms with 4 or 5 valence electrons may lose or gain.

On #14, calculate the number of protons, neutrons, and electrons for sulfur and draw its Bohr diagram.

Bohr Diagrams Sulfur Period 3 Electrons 16 The electron configuration for Sulfur is Is its outer shell full? S

On #15, calculate p,n,e for the 6 atoms and draw their Bohr diagrams. As you are working, if you get stuck, ask for help. We’ll do Lewis Structures tomorrow.

Stop here.

Bohr Diagrams Try the following elements on your own: a)H b)He c)O - 8 electrons d)Al e)Ne f)K O

Let’s practice on your “Bohr Model Practice” sheet as we use the SmartBoard atom models. Atom model practice.notebook

Bohr Diagrams In your notebook, try the following elements on your own: a)H b)He c)O d)Al e)Ne f)K C

And that is Step 1 toward making your own periodic table – How to Draw Bohr Diagrams

Now, on your pink worksheets, draw Bohr diagrams for the remaining elements.

Bohr Diagrams Try the following elements on your own: a)H – 1 electron b)He c)O d)Al e)Ne f)K H

Bohr Diagrams Try the following elements on your own: a)H b)He - 2 electrons c)O d)Al e)Ne f)K He

Bohr Diagrams Try the following elements on your own: a)H b)He c)O d)Al - 13 electrons e)Ne f)K Al

Bohr Diagrams Try the following elements on your own: a)H b)He c)O d)Al e)Ne - 10 electrons f)K Ne