Elements combine to form compounds n n Compounds
Elements combine to form compounds n n Compounds have different properties from the elements that make them. Compounds are substances made of atoms of two or more different elements. The atoms of different elements are held together in compounds by chemical bonds. The properties of a compound depend on the bonds and how the atoms are arranged.
Elements combine to form compounds continued… Compounds have a specific ratio of elements. Ex: H 2 O * Two atoms of Hydrogen for every one atom of Oxygen * Ratio is 2: 1 n
Chemical Formulas n An expression that shows the number and types of atoms joined in a compound. n Subscript numbers are used with symbol of element to show many atoms of that element are present.
Chemical Formulas n A subscript is a number written to the right of a chemical symbol and slightly below it. Ex: CO 2 The chemical formula shows one carbon atom bonded to two oxygen atoms.
Same Elements, Different Compounds n Different compounds can be made using the same elements, but in different ratios. Ex: H 2 O, ratio 2: 1, hydrogen to oxygen H 2 O 2, ratio 2: 2, hydrogen to oxygen
To sum up… Each symbol in a formula represents an element. - If only one atom of an element is present in the compound, no subscript is used. - If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript.
Another example…
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