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Elements and Periodic Table

Elements as Building Blocks

As you probably saw, the periodic table is organized like a big grid. The elements are placed in specific locations because of the way they look and act. If you have ever looked at a grid, you know that there are rows (left to right) and columns (up and down). The periodic table has rows and columns, and they each mean something different.

You've got Your Periods...

Periodic Table showing Periods Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different period (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of atomic orbitals. Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.

...and Your Groups

Periodic Table showing Groups Now you know about periods. The periodic table also has a special name for its columns. When a column goes from top to bottom, it's called a group. The elements in a group have the same number of electrons in their outer orbital. Those outer electrons are also called valence electrons. They are the ones involved in chemical bonds with other elements.

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 some exceptions to the order when you look at the transition elements, but you get the general idea. Transition elements start to add electrons to the second-to-last shell.

Two at the Top

Periodic Table showing hydrogen and helium Hydrogen (H) and helium (He) are special elements. Hydrogen can have the talents and electrons of two groups: one and seven. To scientists, hydrogen is sometimes missing an electron, and sometimes has an extra one. Helium is different from all of the other elements. It can only have two electrons in its outer shell. Even though it only has two, it is still grouped with elements that have eight (i.e., noble gases). The noble gases and helium are all "happy," because their outermost electron shell is full. The elements in the center section are called transition elements. They have special electron rules too.

Next Stop On Chem4Kids Tour
Next Page on Elements
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- Overview
> Periodic Table
- Element List
- Families
- Halogens
- Noble Gases
- Metals
- Alkali Metals
- Alkaline Earth
- Transition Metals
- Lanthanide
- Actinide


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