Periodic table is the representation of elements in an order
The history of periodic table can be summarized as
a) 1829 : Johann Dobereiner proposed the triad rule. According to him we can classify the elements in a triad where the atomic mass of middle element is average of atomic mass of the near by two atoms.
For example : Li, Na and K is a triad. Where atomic mass of Na is average of atomic mass of K
atomic mass of Na = 7+ 39 / 2 = 23
However, with the further discovery of elements the law was rejected.
b) 1864 : John Newland proposed the law of octave. According to him we can arrange the elements in a set of seven elements where the property of second set of seven elements will resemble the properties of first of seven elements or property will be repeated after seven elements. This was also rejected due to its limited applicability.
c) Meyer : He arranged some 28 elements into six different families based on their atomic masses. The members of each familiy shared some common properties.
d) 1869 : Mendleev : He actually developed a periodic table based on atomic mass of elements. He arranged the elements into groups and periods. He even left space for some undiscovered elements, which were later on discovered.
e) 1916 : Henry Moseley : He finally arranged elements based on their atomic number based on X-ray studies. He proposed the modern periodic law that the periodic properties of elements are due to atomic number of elements.
Ask your lab manager for instructions. If you happen to be the lab manager, take out the container (making a note of where it is), find the culprit, and try to figure out what might be in the beaker so you can know how to properly dispose of it.
Proper safety measures should be followed.
<h2>
What are the safety measures in chemistry lab?</h2>
In the lab, always use the proper eye protection, such as chemical splash goggles. When handling hazardous items, put on the disposable gloves that the laboratory has given. Before leaving the lab, take the gloves off. Put on a full-length, long-sleeved lab coat (apron) or apron that can withstand chemicals.
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Answer:
Explanation:
Each value on the scale represents 10 times the previous value.
Subtract 1 from 6, so 10 to the power of 5 is the difference.
Answer:
<h3>F=4k.gm/s^2</h3>
Explanation:
<h3>F=m×a</h3><h3>f=2k.g×2m/s^2</h3><h3>f=4k.gm/s^2</h3>
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