Chemistry · Periodicity in Elements
Work through this past-paper style MCQ, then read the full explanation. Practice more chemistry questions on mMCQ with adaptive practice and topic analytics.
Along a period, atomic radius decreases. This gradual decrease in radius is due to:
- A
Increase in number of electrons in valence shells
- B
Increase in number of protons in the nucleus
- C
Decrease in number of shells
- D
Increase in number of shells
Along a period, the number of shells increases (electrons are added to the same principal energy level), and the atomic number increases. More protons attract the valence electrons. Electrons are gradually pulled closer to the nucleus because of the increased positive charge.
This option is not correct because it is not the primary reason for the decrease in atomic radius along a period. Although the number of electrons in the valence shell does increase as we move across a period, it is the increasing positive charge in the nucleus that has a more significant effect on atomic radius.
As we move across a period from left to right in the periodic table, the number of protons in the nucleus increases, which leads to a stronger positive charge in the nucleus. This increased positive charge attracts the electrons more strongly, resulting in a smaller atomic radius.
This option is incorrect because the number of shells remains constant along a period. The period represents the horizontal rows in the periodic table, where the number of shells (energy levels) does not change but the number of electrons in the outermost shell and the number of protons in the nucleus increase.
This option is incorrect because the number of shells remains constant along a period. The period represents the horizontal rows in the periodic table, where the number of shells (energy levels) does not change but the number of electrons in the outermost shell and the number of protons in the nucleus increase.
Tagged under Chemistry · Periodicity in Elements · 2013