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The concept of avogadro's number and mole through the atomic masses of elements and their combinations. It discusses how scientists discovered the need for specific ratios of elements to form molecules and how the periodic chart helps predict such combinations. The document also introduces the concept of one mole of an element or compound and avogadro's number.
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Scientists were finding that elements combine in ratios of the elements by mass to form molecules. The periodic chart becomes a handy reference tool to look up the atomic mass of an element and predict how much of it is needed to mix with another element.
Lithium has an atomic number of 3…it has 3 protons. It has an atomic mass (red arrow) (sometimes called atomic weight) of 6.
Sodium has an atomic number of 11…it has 11 protons. It has an atomic mass (sometimes called atomic weight) of 22.
Chlorine has an atomic number of 17…it has 17 protons. It has an atomic mass (sometimes called atomic weight) of 35.
Scientists, through experiments, found that based on atomic weights some elements combines in a 1:1 ratio BY ATOM. This is true for sodium (Na) and Chlorine (Cl). Since sodium has less mass than chlorine they found they needed to weigh out more chlorine…but how much?
BY MASS they combine on a 22.99 gram to 35.45 gram ratio.
The atomic masses of many elements were discovered by mixing different amounts of elements and finding out how much was need to make molecules.
