Classification of Elements Flashcards
(42 cards)
Size of an atom
1.2 A°
Basic unit of all matter
Elements
In 1800, only ____ elements were known
31
By 1865 ____ elements were discovered.
More than 63
At present ___ elements are known
118
Why do we need to classify elements
•There are a huge number of elements discovered and yet to be discovered.
•To rationalize the known chemical facts about elements.
•Predict new elements along with their properties to further the studies.
The German chemist,_____ in
early 1800’s was the first to consider the idea
of trends among properties of elements.
Johann Dobereiner
Law of triads was proposed in the year
1829
Who,in which year arranged the then known elements in order of
increasing atomic weights and made a
cylindrical table of elements to display the
periodic recurrence of properties?
French geologist,
AEB de Chancourtoise in 1862.
Who,in which year proposed law of octaves?
The French chemist,John Alexander Newlands in 1865.
Which classification resembles the pattern of musical notes?
Law of octaves (1865)
Newlands law of octaves was true for only elements upto _____.
Calcium
What was awarded to Newlands for his work of Law of Octaves?
He was awarded
Davy Medal in 1887 by the Royal Society,
London
The Periodic Law, as we know it today owes
its development to ____ and ____.
Russian chemist, Dmitri
Mendeleev (1834-1907) and the German
chemist, Lothar Meyer (1830-1895)
Lothar Meyer
plotted the physical properties such as atomic
volume, melting point and boiling point
against atomic weight and obtained a
periodically repeated pattern. Unlike
Newlands, Lothar Meyer observed
A change in length of the repeating pattern
By the year ____ Lothar Meyer had developed a table of the elements that closely resembles the modern periodic table.
1868
Medeleeves periodic law states
The properties of the elements are a
periodic function of their atomic
weights.
The two aspects Mendeleev relied on, while making the periodic table.
•the similarities in the empirical formulas
•properties of the compounds formed by the
elements.
Site an example for Mendeleev not following his own periodic law.
iodine with lower atomic weight
than that of tellurium (Group VI) was placed
in Group VII along with fluorine, chlorine,
bromine because of similarities in properties
What is Eka Aluminum
Gallium
What is Eka Silicon
Germanium
Mendeleeves periodic table was published in the year
1905
How did Henry Moseley show that the atomic number is a more fundamental
property of an element than its atomic mass?
In 1913, the
English physicist, Henry Moseley observed
regularities in the characteristic X-ray spectra
of the elements. A plot of ν (whereν is
frequency of X-rays emitted) against atomic
number (Z ) gave a straight line and not the
plot of ν vs atomic mass.
Modern periodic law states
The physical and chemical properties
of the elements are periodic functions
of their atomic numbers.
