Question

From the following element${}_{19}{}^{39}\mathrm{A},{}_{14}{}^{28}\mathrm{B},{}_8{}^{16}\mathrm{C},{}_{18}{}^{40}\mathrm{D}$, which elements belong to the same period?

Answer 1

Periods in the periodic table:

1. Periods are the horizontal rows of elements with similar properties on the periodic table.
2. Along the periodic table, they are numbered 1 to 7, moving from left to right.
3. Elements belonging to the same period have the same valence shell.
4. Element ${}_{14}{}^{28}\mathrm{B}$has an atomic number$=14$ with an electronic configuration$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^2$.
5. Element ${}_{18}{}^{40}\mathrm{D}$ has an atomic number$=18$ with an electronic configuration$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^6$.
6. Element ${}_{14}{}^{28}\mathrm{B}$ represents silicon and element ${}_{18}{}^{40}\mathrm{D}$ represents Argon.
7. Both these element belongs to the $3^{\mathrm{rd}}$period of the periodic table.

Therefore, From the given elements ${}_{14}{}^{28}\mathrm{B}$ and ${}_{18}{}^{40}\mathrm{D}$ belongs to the same period.