I Love 1s 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 6d1 5f3

If you can understand the title of this post, congratulations to you, you have learned one of the fundamental topics of chemistry. "The Aufbau Principle" states that electrons fill orbitals from the lowest possible energy states before filling higher states. So don't marvel that you can see that 3 comes first then 4 then back to three. If you only know how the periodic table is structurized, you can easily tell what comes next. Chemistry is a douchebag, so expect many exemption just like why is it that H is in line with the Alkali Metals if it's a gas? Well, I can answer that kind of easy questions. Simply because H can act like a metal(the one that donates their electron) and non-metal(the one who receives the donated electron and by nature H is a gas). There are also exemption here just like U, Cu, Cr, Ag and other elements that don't follow the usual step of the aufbau principle.

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from chemistry.about.com

From here we can see that in order to predict the electron configuration of an element, we must follow the arrangement on how electrons are distributed from each orbital. A knowledge and a visualization of the periodic table is needed for you to easily tell what comes next after every orbital. For example you know that 1s2, 2s2 2p4 is the electron configuration of O because you know that its position is at the fourth column of the p orbital and it's at the second column that's why it ends at 2p4. Another thing! Just by knowing it's position on the periodic table, you can easy tell its last orbital and electron at its last orbital. We know that Ca(Calcium) is at the 4th row, second column of the s orbital so it ends at 4s2. Just supply the rest just before 4s2 just by following the aufbau principle! (Just take note of some elements that don't follow this trend)

Congratulations! You learned how I can easily tell the electron configuration of an element. Spill the beans guys! Share if you like. And party while you can because this is the easiest parts of Chemistry. Don't hate this subject, beside its fun and exciting(you can see liquids when dissolve with each other forms a solid! a flying ring then dissolve to the air), it's very informative. You'll learn from this course why ethylene glycol is used as antifreeze in radiators instead of Sodium Chloride(your table salt that you have whenever you want to eat unripe mango without your alamang). I love this subject so much! I encourage you to study and enjoy this course the way I enjoy it. :))))