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.
<u>Given:</u>
Time taken by the electromagnetic radiation, t = 33 fs
<u>To determine:</u>
The distance (d) travelled
<u>Explanation:</u>
Time taken = 33 fs (femtosecond)
1 fs = 10⁻¹⁵ s
Thus t = 33 *10⁻¹⁵ s
Speed of electromagnetic radiation = 3*10⁸ m/s
Distance = Speed * Time = 3*10⁸ ms-1 * 33*10⁻¹⁵ s = 99*10⁻⁷ m
Ans: distance traveled = 9.9*10⁻⁶ m
Answer:
The molar concentration of 
ions in the given amount of sample is 
Explanation:
Given that,
Mass of sample = 21.5 g
0.07 % (m/m) of copper (II) sulfate in plant fertilizer
This means that, in 100 g of plant fertilizer, 0.07 g of copper (II) sulfate is present
So, in 20 g of plant fertilizer
,
of copper (II) sulfate is present.
To calculate the molarity of solution, we use the equation:
Mass of solute (copper (II) sulfate) = 0.0151 g
Molar mass of copper (II) sulfate = 159.6 g/mol
Volume of solution = 2.0 L
The chemical equation for the ionization of copper (II) sulfate follows:
1 mole of copper (II) sulfate produces 1 mole of copper (II) ions and sulfate ions
Molarity of copper (II) ions =
Hence, the molar concentration of ions in the given amount of sample is
