Today is Tuesday, September 15 th, 2015 Pre-Class: We will be starting with a concept map today,...
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Transcript of Today is Tuesday, September 15 th, 2015 Pre-Class: We will be starting with a concept map today,...
Today is Tuesday,September 15th, 2015
Pre-Class:We will be starting with a concept map today, followed by some information…
and stuff…
In This Lesson:Compounds,
Electron Configuration(Lesson 3 of 9)
Today’s Agenda
• Concept map review.• Review of Guiding Questions.• Understand compounds.• Diagram electron configuration.• Learn bonds (soon).• Properties of Water (not as soon but still soon).
• Where is this in my book?– Academic: p. 35 and following…– Honors: p. 19 and following…
By the end of this lesson…
• You should be able to identify the basic structure of compounds.
• You should be able to properly place electrons around a nucleus with respect to energy levels.
Atom Concept Map Review
• Everyone should copy this down.– Makes for a great study guide…
• Volunteer(s)?
Guiding Questions
• Recently we looked at a series of what I called Guiding Questions.
• For review, here they are…
Guiding Questions(Write these down)
1. Is it okay to use the number of electrons as a measure of atomic number?
2. What happens if you remove or add a proton?3. What happens if you remove or add a neutron?4. What happens if you remove or add an electron?
Guiding Question 1
• Is it okay to use the number of electrons as a measure of atomic number?– No – in ions, the number of electrons does not
equal the atomic number.
Guiding Question 2
• What happens if you remove or add a proton?– Adding a proton changes the element!– This does not often happen in nature.– Let’s say you have Hydrogen. It’s got one proton. – We add a proton, so now it has two. Which
element has two protons?• Helium.
Guiding Question 3
• What happens if you remove or add a neutron?– You’ll create a new isotope.– Same element, same number of protons, new
number of neutrons, new atomic mass.
Guiding Question 4
• What happens if you remove or add an electron?– You’ll create an ion.– An ion is an electrically-charged atom.
Compounds
• As we learned recently (briefly), a compound is a chemical combination of two or more elements.– Examples of compounds:
• Water• Salt• Hydrochloric Acid (stomach acid)• Sulfuric Acid (“ouch” acid)• Carbon Dioxide• Carbonic Acid (similar to soda water)• Glucose (simple sugar)
Compounds
• In compounds, elements are held together by some kind of bond (more on bonds later today/tomorrow).– The smallest unit of an element is called an atom.– The smallest unit of a compound is called a molecule.**
• Compounds generally form through a chemical reaction, in which bonds are broken, rearranged, or formed.– Speaking of chemical reactions…– Video! Chemical Reactions – NOVA
Compounds vs. Elements
• Remember that writing an element is as easy as its abbreviation:– H, Cu, Hg, Li, He, O, C
• Writing a compound means writing all the elements in the compound, as well as how much are in there.– Examples next slide…
Compounds
• Compound Examples:– Water (H2O – 2 Hydrogen atoms and 1 Oxygen atom)– Salt (NaCl – 1 Sodium atom and 1 Chlorine atom)– Hydrochloric Acid (HCl – 1 Hydrogen and 1 Chlorine)– Sulfuric Acid (H2SO4 – 2 Hydrogen, 1 Sulfur, 4 Oxygen)
– Carbon Dioxide (CO2)
– Carbonic Acid (H2CO3)
– Glucose (C6H12O6)
Making Compounds
• As we said, compounds form from bonds.• To understand bonds, we need to understand
electron configuration.• Electron configuration refers to how the
electrons are organized in that cloud around the nucleus.
• Note (but not in your notebooks): What you’re about to hear is the simplified biology version. The chemistry version is MUCH more complicated/realistic.
Electron Configuration
• In any given atom’s electron cloud, we say there are energy levels or energy shells.
• By this, we mean that there are levels closer to the nucleus (lower energy levels) and levels further from the nucleus (higher energy levels).
• Picture on next slide…
Electron Configuration
http://www.physics.uiowa.edu/adventure/fall_2005/oct_15-05/energy_levels.gif
• The electrons in the outermost energy shell (however far out that may be) are called valence electrons.
• Valence electrons are the only ones that matter in bonding.
Electron Configuration
• “Filling” electron shells with electrons is easy.• You already know how to calculate the total
number of electrons in an atom or ion.• Fill the shells in a 2-8-8 pattern.– We won’t often be going higher than atomic
number 18 in this class.– Example on next slide.
Electron Configuration
• Let’s fill the shells of Aluminum, atomic number 13. This means there are how many electrons in an uncharged atom?– 13
• Remember the 2-8-8 pattern!• First shell: 2• Second shell: 8• Third shell: 3– 3 valence electrons, and the third shell is the valence
shell in this case.
From ChemicalElements.com
• Take a look at the aluminum atomic diagram to the right. What do you see?
• Another place to look:– David’s Whizzy Periodic Table• http://
www.colorado.edu/physics/2000/applets/a2.html• Linked on my website.
Electron Configuration
• Now it’s your turn.• Fill the shells of the following atoms in your notebooks, and
write how many valence electrons there are:– Carbon– Oxygen– Beryllium– Fluorine– Hydrogen– Helium– Neon– Magnesium– Sulfur
Electron Configuration
• Carbon (Atomic Number 6)– 2, 4 [4 valence electrons]
• Oxygen (Atomic Number 8)– 2, 6 [6 valence electrons]
• Beryllium (Atomic Number 4)– 2, 2 [2 valence electrons]
• Fluorine (Atomic Number 9)– 2, 7 [7 valence electrons]
Electron Configuration
• Hydrogen (Atomic Number 1)– 1 [1 valence electron]
• Helium (Atomic Number 2)– 2 [2 valence electrons]– Notice something about helium?
• Neon (Atomic Number 10)– 2, 8 [8 valence electrons]– Notice something about neon and helium?
Electron Configuration
• Magnesium (Atomic Number 12)– 2, 8, 2 [2 valence electrons]– Notice something about magnesium and
beryllium?• Sulfur (Atomic Number 16)– 2, 8, 6 [6 valence electrons]– Notice something about sulfur and oxygen?
Electron Configuration
• What’s going on with helium and neon?– How many valence electrons?
• 2 and 8
– How many more can you fit in their outermost energy shells?• None! The valence shells are at capacity!
• These, and all the elements in the same column below them, are called the noble gases.
• Because their valence shells are full, they don’t really react with anything.– They also were among the last elements to be discovered.
• Think of a snooty “noble” person. That’s how they were named!
Electron Configuration
• Now what about Beryllium and Magnesium?– How many valence electrons for each?– 2!
• And how about Oxygen and Sulfur?– 6 each!
• And what about all of their locations on the table?
Electron Configuration
• There is a pattern to the periodic table for valence electrons!
• Work by columns (which are called groups).• Start from the left and ignore the lower
middle part.– The first column or group has 1 valence electron,
the second has 2, et cetera.• Rows, by the way, are called periods.– Hence, periodic table of elements.
Dmitri Mendeleev
• Looks like he was on to something when he arranged the table…
http://reich-chemistry.wikispaces.com/file/view/Dmitri_Mendeleev.jpg/98117907/Dmitri_Mendeleev.jpg
One last thing…
• If you’re dealing with an ion (say for example Al3+), make sure you get the new number of electrons.
• Al3+ has 13 protons and 10 electrons, so the arrangement is:– First shell: 2– Second shell: 8
• Total: 10 electrons
And so now we dothe Review and WhipAround…
• First, play Electron Configuration Matching Game on Quia.
• Then, try Atomic Structure and Electron Configuration Battleship.
• Then, try Atomic Structure Review Quiz.– Write both your names in the survey question.
• Find some space in your notebook and write down two things you learned about:– Electron Configuration– Compounds