three elements A,B and C have atomic no. 7,8, and 9 respectively
what would be their positions in the modern periodic table (mention group and periodic both)
arrange A,B and C in the decreasing order of their size
which one of the three elements is the most reactive and why?

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Solution

Atomic number 7, 8 and 9 belong to groups 15,16, and 17 respectively on the basis of valence electron they occupy. All belong to period 2. They are N, O and F respectively.
In the period atomic size decreases from left to right. Hence decreasing order of size is N>O>F
F is more reactive because it has 7 electrons in valence shell and requires only one electron. This makes it more reactive element.

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three elements A,B and C have atomic no. 7,8, and 9 respectively what would be their positions in the modern periodic table (mention group and periodic both)arrange A,B and C in the decreasing order of their size which one of the three elements is the most reactive and why?

three elements A,B and C have atomic no. 7,8, and 9 respectively
what would be their positions in the modern periodic table (mention group and periodic both)
arrange A,B and C in the decreasing order of their size
which one of the three elements is the most reactive and why?