chem既skeletal formula................

Skeletal formula is a form of structural formula to represent an organic compound.

Rules to write skeletal formulae:
1. All covalent bonds are draw as sticks.
2. All C atoms are not denoted by there symbols. They are implied to exist at each vertex.
3. All H atoms bonded to C atoms, are not denoted by their symbols. (The number of H atoms attached to a particular C atom is equal to the difference between 4 and the number of bonds drawn to that C atom.)
4. All H atoms bonded to atoms other than C (e.g. H atom in -OH group) must be shown.
5. All atoms other than C and H atoms must be shown.

For example, the normal structural formula and the skeletal formula of butan-2-ol are shown below:


圖片參考：http://www.chemguide.co.uk/basicorg/conventions/butan2olskel.GIF

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Besides, skeletal formula is also used as a form of 3-dimensional diagram to represent an organic diagram. The principle is as same as above.

An example is shown below:

圖片參考：http://content.answers.com/main/content/wp/en-commons/thumb/d/d3/180px-Cystine-skeletal.png