CBSE - IX - Chemistry - Atoms and Molecules
What Is Actually Mole Concept?
Moles of Compounds
The concept of a mole can be applied to compounds as well as elements. A mole of a compound is what you have when you weigh out, in grams, the formula weight of that compound. (Use the molecular weight if the compound is a molecular material.) For example, the formula weight for HF is 20.0. That means that one mole of HF weighs 20.0 grams, and you can use that relationship to convert back and forth between grams and moles.
Moles of Molecular Elements
Special care must be taken when dealing with moles of a molecular element. If someone talks about "so many moles of hydrogen," it is necessary to find out whether they mean moles of atomic hydrogen (H, 1.0 g/mole) or moles of molecular hydrogen (H2, 2.0 g/mole). To avoid mistakes, look for a formula or consider the context.
An atom's electron shells are filled according to the following theoretical constraints:
- Each s subshell holds at most 2 electrons
- Each p subshell holds at most 6 electrons
- Each d subshell holds at most 10 electrons
- Each f subshell holds at most 14 electrons.
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