Atomic size increases down a group and descreases across a period because when going down a group number of shells of elements increases and across periods number of shells stay the same but the number of electrons increases which will cause too much weight on the atom and it gets diminished. so according to that:
3. A
4. B
5.C( because noble gases are stable)
1.A
2.C
Answer:
3. (a)
4. (c)
5. (c)
1. (a)
2. (b)
Explanation:
3.
from left to right across a period the atomic size decreases because the nuclear charge increases while the no. of valence shells remains constant. The strong electrostatic force between the nucleus and the electrons draws the outermost shell inwards resulting in decrease of atomic radius from left to right.
so, the answer is a. atomic radius of elements decreases from left to right.
4.
Argon has the largest atomic size. Yeah I know, I just said that the atomic radius decreases on moving across a period BUT Nobel gases are exception. In fact they have the largest atomic size in a period. This is because their valence shells are complete and this cause the internal electrons to repel each other thus pushing the valence shell away from the nucleus causing the atomic size to increase.
so the answer is c. Argon
5.
Halogens have the smallest radius in a period. Because their nuclear charge is greatest in a period.
so the answer is c. Halogens
CONCLUSION :-
1.
since, the atomic size increases down the group and decreases along a period the biggest elements are arranged in the bottom and in the left side of the periodic table.
so option a.
2. For metals the atomic radius is directly proportional to their reactivity
metals have to lose electrons in order to become stable and the easier they lose electrons the higher is their reactivity also that a metal will lose electrons easily if it's atomic radius is large so that the outermost electrons are loosely bonded and can be withdrawn easily.
so option. b.
