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Berzelius was an orphan in Sweden, brought up by a horrible stepfather. He had to work on the farm and was forced to share his “room” with the supply of potatoes. Fortunately, his father made sure the potatoes didn’t freeze during winter so neither did Berzelius. From high school, Berzelius went on to university where he became interested in experimental chemistry.
What did Berzelius do?
When he heard of Dalton’s measurements, he set out to do his own measurements on the atomic masses. His advantage was that he also heard about Humphrey Davy’s experiments so he knew the amount of atoms in each molecule. He discovered that when you pass electricity though water, you get twice the amount of hydrogen gas as you do oxygen gas. With this, he conclused that a molecule of water consists of one atom of oxygen and two of hydrogen.
Berzelius’ atomic theory
1. All atoms are spherical.
2. All atoms are the same size.
3. Atoms have different masses.
4. Atoms joined together in fixed proportions, by an electrochemical reaction. Some atoms are positive and others are negative.
Dalton could not accept Berzelius’ electrochemical combination, but at the same time could not explain why atoms joined together in fixed proportions.
Chemical symbols
Berzelius thought that chemical symbols should be letters. He took the first letter of the Latin name of each element. When the letters were the same, he used both the first letter and the next different letter. Berzelius’ symbols are used in today’s Periodic table.
Opdrachten
7. Use a BINAS, a periodic system or the internet to find the relative mass of the next few elements.
Note: It's called a relative atomic mass because the mass of hydrogen was "set" at 1 so all the other masses are just "the amount of times heavier than hydrogen".
8. Who was closest to the modern relative atomic masses?
9. Name two reasons for this.
10. How did Berzelius think that atoms joined together to make compounds?
11. Calculate de mass of the following compounds, using the relative atomic masses from a periodic table.
a) Water
b) Carbon dioxide
c) Oxygen
d) Methane
e) Sulphur trioxyde
f) Tetraethyl lead
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