Electrons and their Clouds

Understanding electrons will allow you to understand…. Why chemical reactions occur Why some atoms prefer to become ions, while others remain atoms. Why some elements are reactive while others are not. Specifically, it is important to know… 1) how many electrons are in an atom 2) where they are located ^

Electron Configuration… Describes the location of electrons within the atom Will identify the shape of the electron clouds that the electrons form as they move. Will use numbers and letters to describe an electron’s location and its cloud. ^

1s2 An example The “s” tells you the electron’s cloud shape. In this case it’s a spherically shaped cloud. It is called the s orbital. Orbital= Shape 1s2 The “2” simply tells you how many electrons are in this cloud. The “1” tells you how far from the nucleus the electrons can go. In this case 2 electrons are creating the cloud. In this case, its in the 1st energy level, which is the closest level to the nucleus. Note: Each orbital can only hold 2 electrons. They must have opposite spins.

In summary… 1s2 Represents 2 electrons forming a spherical cloud that is in the energy level closest to the nucleus.

A new view of the atom This was the old way…

3s2 2s2 1s2 2py2 This is a more accurate model. 3pz2 2pz2 3px2 2px2 Nucleus 3pz2 2s2 2pz2 1s2 3px2 2px2 2py2 3py2 This is a more accurate model.

Another view of this model… Here’s a better 3D representation

These all overlap within the 2nd energy level. 1s2 2s2 2px2 2py2 2pz2

The Basics of Stability As electrons move around an atom, they shift its orientation about. This electron movement makes the atom tend to toss and turn. Atoms with “high energy” toss and turn more than those with low energy. If the placement of electrons is more uniform… the flipping about is minimized and the atom has lower energy/less movement… IT IS MORE STABLE!

Electron Placement and Stability 3pz2 2s2 1s2 2pz2 3px2 2px2 2py2

Maximum Stability There are various levels of stability However, maximum stability occurs when… An atom has a completely filled outermost energy level Stable ions will have electron configurations identical to one of the noble gases

Bell work: Date: [Describe stability of atoms in terms of movement and energy]

= = = Orbital Diagrams 1) A Box symbolizes an orbital (1 cloud) Orbital/electron cloud 2) An arrow (up or down) represents an electron = electron 3) Arrows’ directions show spin of electrons = Electrons in a cloud that have opposite spins so they can share the same orbital.

Practice with Electron Configurations Hydrogen He (a very stable atom) Lithium Beryllium Boron (Draw orbitals picture) Carbon* we’ll learn later

Practice with Electron Configurations and orbital diagrams Nitrogen (draw orbitals picture) oxygen Neon (a very stable atom)

Combining the p orbitals The 2px2, 2py2, and 2pz2 orbitals will now be put together as 2p6.

Some important questions… A) How many electrons are in the outermost energy level (the one farthest from the nucleus)? B) How many unpaired electrons are there within the atom? C) How will it become stable? D) What is the symbol for the stable ion/atom? E) What noble gas does it resemble when stable? F) What Energy level is completely filled when stable?

All the way through 1s2 2p6 2s2 3s2 3p6 4s2 *3d10 4p6 5s2 4d10 5p6 In this class, the furthest we will go is the element xenon (Xe). As we do this one, you will learn a new orbital shape known as the d orbital. It will have 5 clouds, each with 2 electrons (10 total electrons) 1s2 2p6 2s2 3s2 3p6 4s2 *3d10 4p6 5s2 4d10 5p6

Lewis electron dot structure The X shown below could be the symbol for any element. Only the outermost electrons will be shown in a Lewis diagram. Why? This is the pattern to show where electrons are 1 2 X 5 3 8 6 4 7 Let’s do Ne as we go through this.

Practice… Fluorine Sodium Phosphorus Magnesium

Mini warmup: Bellwork: Date: Write the electron configuration and orbital diagrams for the following elements. Answer the regular questions. [ lithium nitrogen magnesium carbon (what it seems it should be)]

“Reading” the Periodic chart! http://www.webelements.com/ Don’t be! It’s fun and makes electron configurations easier!

Shorthand Electron Configurations This is a shorter way to do e- configurations Steps… 1) Write the symbol of the element you are doing 2) Find the noble gas (family VIII) that comes before the element you are doing... 3) put that noble gas in [brackets] 4) Starting with that noble gas, finish the electron configuration http://www.webelements.com/

Ciao… it’s been fun.

Bellwork: date: [1) Selenium 2) Chromium] a) Write the electron configuration. Include orbital diagrams above configuration. b) How many outermost electrons are there? c) How many unpaired electrons are there? d) How will it become stable? (gain/ lose+ number) e) What will the symbol of the stable ion be? f) Draw the Lewis electron dot structure for the atom.

Family and Period Family/group- vertical columns on the periodic chart. They use Roman numerals. Period- horizontal rows on the periodic chart. They use normal numbers. What is in family II period 3? What is in group III period 2? Group IV, period 3? Period 1 group V? The family/group number tells you how many electrons are in the outermost electron energy level. The period tells you the outermost energy level.

Bellwork: Date: 1) Strontium 2) Selenium 3) manganese a) Write the short hand electron configuration b) Include orbital diagrams. c) How many outermost electrons are there? d) How many unpaired electrons are there? e) How will it become stable? (gain/ lose+ number) f) What will the symbol of the stable ion be? g) What noble gas does it resemble when stable? H) Lewis structure?

Bellwork: Date: [1) rubidium) 2) sulfur 3) magnesium 4) arsenic] a) Write the SHORTHAND electron configurations b) Include orbital diagrams. c) How many outermost electrons are there? d) How many unpaired electrons are there? e) How will it become stable? (gain/ lose+ number) f) What will the symbol of the stable ion be?