Question

pls tell me answers of both questions i need your helpp!!p​

Answer 1

1. Answer:

element are arranged in increasing order of atomic numbers.

element in Modern Periodic Table arrange in 7 periods and 18 group.

horizontal rows are called periods and vertical rows are call groups.

Answer 2

Answer:

1; The periodic table is divided into horizontal raws called periods or series and the vertical colums are called groups or families.

• periods are assigned in arabic numerals 1 to 7
• families are assigned in Roman numerals ( paired with a or b) 1A to 8A, 1B to 8B.

2 , in 1869 russian chemist Dimitri mendeleev started the development of the periodic table, arranging chemical elements by atomic mass he predicted the discovery of other elements and left spaces open in his periodic table for them. in 1886 french physicts Antoine first discovered radioactivity....

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