With reference to long form of the periodic table fill in the blank spaces with appropriate words.
The first period has ____________ elements and is called ___________ period.
A
two
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B
very short
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Solution
From the long form of periodic table, it can be seen that the first period has two elements i.e.; Hydrogen (H) and Helium (He).
Due to the least number of elements in a period, this periods is called as the very short period.
Period number 2 and 3 has eight elements each and are called as short periods.
Period number 4, 5 and 6 have 18, 18 and 32 elements respectively and are known as long periods.
Long form of periodic Table: In the long form of the periodic table, elements are arranged in the order of their increasing atomic number in the tabular form.
It has 18 vertical groups or columns and 7 horizontal rows or series.
The long form of periodic table follows modern periodic law.
Therefore, the first period has two elements and is called very short period.
