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Atomic Structure

Classification of Matter
Naming Compounds
Writing Formulas
The Periodic Table
Atomic Structure
Mole Calculations

What makes up an atom?


An atom is made up of electrons (-), protons (+), and neutrons (neutral charge). The electrons travel around the nucleus in little things called orbitals. Atomic orbitals are s,p,d, and f. The 1st energy level can only hold 2 electrons, the second holds 8, the third holds 18, and the fourth holds 32. How do you know which orbital the electrons are in? Here are some ways to find out:
Orbital Configuration
In orbital configuration, you can see the orbitals that the electrons fall in.
Example: Phosphorus
1. Find the number of electrons in phosphorus
2. Every space holds 2 arrows, so fill them up, up to 15, but make sure that if you start a section, you don't start doubling up arrows until you get one arrow in each slot
3. So your result would be...(see "Orbital Configuration Answer")
4. Written, it would be 1s2 2s2 2p6 3d5
Dot Diagram
How many valence electrons are there? The # of valence electrons is determined by the column number. So, take oxygen for example. It's in the sixth column. Use this form when writing a dot diagram:
                                       3     6
                                   4             2                                                                      
                                   7       1
                                      5       8 
When actually doing a dot diagram, you would put the symbol in instead of the X. In this case, O would replace the X. Since there are 6 valence electrons, you dot where it says 1,2,3,4,5, and 6. See "Dot Diagram Answer".
Bohr Model
The Bohr Model is a tricky one. You pick an element (let's use phosphorus since this is similar to orbital notation). Write the number of protons and the number of neutrons. Draw 4 circles around your numbers (four energy levels). Now go look at the diagram labeled "Bohr Model 1". The colored lines tell you where to draw your lines for the electrons. So, in the 1st energy level, there can only be 2 (1s can only hold 2 electrons), so you draw 2 lines where the 's' area is. Then move on to the next energy level (the next circle). This one can hold 8. So, 2s2, you put 2 lines in the 's' area. 2p6, now you draw 1 line in each of the p areas, then go back and add another one to each area. Add all the lines together and you have 8!
Now move on to the third energy level, which can hold 18. Remember, the total number of electrons is 15, and you already have 8, so you just need 7 more. Fill in the 's' area so you only have 5 left now. Fill up the 3p area with the remaining 5 and you did it! See "Bohr Model Answer".

Orbital Configuration Answer

Dot Diagram Answer



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