pls tell me answers of both questions i need your helpp!!
Answers
Answer 1 :-
• In a modern periodic table, elements are arranged in increasing order of their atomic numbers Ex Hydrogen - 1 , Helium - 2 etc.
• In a modern periodic table, Horizontal rows are called periods and vertical columns are called groups . The modern periodic table contain 7 periods and 18 groups
• In modern periodic table, elements can be broken down into 4 blocks that is S - block, P - block , D - block and F - block
• The elements of group 1 , 2 , 13 , 14 , 15 ,16 and 17 are known as representative elements.
• The elements of group 3 , 4 ,5 , 6 , 7, 8 , 9 , 10 , 11 and 12 are known as transistion elements
• The first period of periodic table contain only two elements that is hydrogen and helium are called shortest period.
• The second and third period contains eight elements called short period.
• The fourth and fifth period contains 18 elements called long period.
• The sixth and seventh period contains 36 elements called longest period.
Answer 2 :-
• Dobereiner was the first scientist who showed the relation between the properties of the elements and their atomic masses
According to Dobereiner, The three elements of a train were arranged in order of their increasing atomic masses, The atomic mass of the middle element is roughly equal to the atomic masses of the other to elements.
Dobereiner could only able to arrange 9 elements That is why his idea was rejected.
• After Dobereiner , Newlands take the plunge to arrange the elements in periodic table and he gave New lands law of octaves
According to Newlands law of octaves, When elements were arranged in horizontal rows in order of their increasing relative atomic masses, The properties of every eighth element were similar to the first one like the eight note of a musical scale .
Newlands law was only applicable upto calcium and because of other limitations the Newlands law of octaves was also rejected.
• The first real breakthrough in the classification of elements was provided by Russian chemist, Dimitri Ivanovich Mendeeleve.
According to Mendeeleve, A periodic table may be defined as an arrangement or a chart which classifies all the known elements with similar properties are placed in the same vertical columns and dissimilar elements are separated from one another.
Mendeeleve also provided one law that is. atomic masses are the fundamental properties of periodic table.
Mendeeleve law was rejected because In some cases, elements with similar properties have been placed in different groups. For example, both copper, mercury have similar properties but Cu has been placed in group I B while Hg has been placed in group II B .
• After Mendeeleve , In 1913 , Henry moseley showed that the atomic number of an element is more fundamental property that it's atomic masses.
In a modern periodic table, The elements are arranged in increasing order of their atomic numbers and this table was based on the electronic configuration of elements
The modern periodic table has cleared all the doubts that was founded in mendeeleve periodic table.
That's how modern periodic table was formed