Question

From the given elements: ${}_{20}Ca,{}_{3}Li,{}_{11}Na,{}_{10}Ne$ choose two elements belonging to the same group in the periodic table.

Answer 1

• The modern periodic table has 18 vertical columns and each one of them accommodates elements with the same number of electrons in its valence shell.
• The electronic configuration of all the given elements,

$$\begin{gathered} {}_{20}Ca\to 2,8,8,2 \\ {}_{3}Li\to 2,1 \\ {}_{11}Na\to 2,8,1 \\ {}_{10}Ne\to 2,8 \end{gathered}$$

• It is evidently seen that Lithium and sodium here have 1 electron in their outermost shell, so they belong to the same group 1 (Alkali metals).
• Hence,${}_{3}Li\mathrm{and}{}_{11}Na$ are the two elements belonging to the same group in the periodic table.