![Corner icon for tutorials on elements and the periodic table. Elements Chalkboard](../art_global/board-element.png)
Elements as Building Blocks
![Elements of the periodic table have similarieites across rows and columns. Elements of the periodic table have similarieites across rows and columns.](art/elem_pertable01.png)
You've got Your Periods...
!["Image of periodic table showing periods as horixontal rows. Image of periodic table showing periods as horixontal rows.](art/elem_pertable2.png)
...and Your Groups
![Image of periodic table showing groups as vertical columnds. Image of periodic table showing groups as vertical columnds.](art/elem_pertable3.png)
Every element in the first column (group one) has one electron in its outer shell. Every element in the second column (group two) has two electrons in the outer shell. As you keep counting the columns, you'll know how many electrons are in the outer shell. There are exceptions to the order when you look at the transition elements, but you get the general idea. Transition elements add electrons to the second-to-last orbital.
For example, nitrogen (N) has the atomic number seven. The atomic number tells you there are seven electrons in a neutral atom of nitrogen. How many electrons are in its outer orbital? Nitrogen is in the fifteenth column, labelled 'Group VA'. The 'V' is the Roman numeral for five and represents the number of electrons in the outer orbital. All of that information tells you there are two electrons in the first orbital and five in the second (2-5).
Phosphorus (P) is also in Group VA which means it also has five electrons in its outer orbital. However, because the atomic number for phosphorus is fifteen, the electron configuration is 2-8-5.
Two at the Top
![Periodic Table showing hydrogen and helium as two top elements. Periodic Table showing hydrogen and helium as two top elements.](art/elem_pertable4.png)
Helium (He) is different from all of the other elements. It is very stable with only two electrons in its outer orbital (valence shell). Even though it only has two electrons, it is still grouped with the noble gases that have eight electrons in their outermost orbitals. The noble gases and helium are all "happy," because their valence shell is full.
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