what is the similarity between doberneir triads and newland's law of octaves
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taking atomic weight as the basic thing is the similarity between dobereiner's triads and newlands law of octaves.
bhavyhans:
but doberneir didn't took atomic masses....he just prepared triads
he prepared triads by taking average of atomiç masses.
he made triads only with the help of atomic weight
thanks dude...
it ok
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Johann Wolfgang Dobereiner was a chemist in the early 1800s. At this time, the periodic table wasn't in existence and some chemists were trying to find a type of organizational system for the known elements. Dobereiner noticed a pattern with certain elements that had similar chemical and physical properties. He called these elements triads. If you put these elements in order of their atomic masses the average of the molar mass of the first and third elements in the triad is the molar mass of the second element. Let's look at an example.
The halogens, chlorine, bromine, and iodine, have atomic masses ≈ 35 g/mole, ≈ 80 g/mole, and ≈ 127 g/mole respectively. These values are rounded to the nearest g/mole. If we take the average of the masses of chlorine and iodine we get:
1/2(35 g/mole + 127 g/mole) = 81 g/mole, which is very close to bromine's atomic mass of 80 g/mole.
There are a few other triads:
lithium, sodium, and potassiumcalcium, strontium, and bariumphosphorus, arsenic, and antimonysulfur, selenium, and tellurium
If you locate these triads on the modern periodic table you will see they are stacked vertically. Diagram 1 has the triads outlined.
Diagram 1. Triads are boxed in.
Newlands' Law of Octaves
Now let's look at another law known as Newlands' Law of Octaves. The prefix octmeans eight, and Newlands' Law of Octaves deals with elements that are eight spaces apart. In the late 1800s, John Newlands put the known elements at the time in order of increasing atomic mass. He noticed that elements that were eight spaces apart had similar chemical and physical properties. For example, sodium has the atomic number 11 and potassium has the atomic number 19. These elements are 8 atomic numbers apart. With our chemistry knowledge today, these two elements are put in the same group because they are so similar in terms of their physical and chemical properties. Newlands observed the same thing without having a modern periodic table.
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The halogens, chlorine, bromine, and iodine, have atomic masses ≈ 35 g/mole, ≈ 80 g/mole, and ≈ 127 g/mole respectively. These values are rounded to the nearest g/mole. If we take the average of the masses of chlorine and iodine we get:
1/2(35 g/mole + 127 g/mole) = 81 g/mole, which is very close to bromine's atomic mass of 80 g/mole.
There are a few other triads:
lithium, sodium, and potassiumcalcium, strontium, and bariumphosphorus, arsenic, and antimonysulfur, selenium, and tellurium
If you locate these triads on the modern periodic table you will see they are stacked vertically. Diagram 1 has the triads outlined.
Diagram 1. Triads are boxed in.
Newlands' Law of Octaves
Now let's look at another law known as Newlands' Law of Octaves. The prefix octmeans eight, and Newlands' Law of Octaves deals with elements that are eight spaces apart. In the late 1800s, John Newlands put the known elements at the time in order of increasing atomic mass. He noticed that elements that were eight spaces apart had similar chemical and physical properties. For example, sodium has the atomic number 11 and potassium has the atomic number 19. These elements are 8 atomic numbers apart. With our chemistry knowledge today, these two elements are put in the same group because they are so similar in terms of their physical and chemical properties. Newlands observed the same thing without having a modern periodic table.
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