Question

The elements of second and third period of the periodic table are given below:
(i) Which atom is bigger in size Li or Be? Why?
(ii) Which one element out of those given above is the most metallic and why?

Answer 1

Answer:

i) Li

The atom of Li is more bigger than Be.

ii) Na

Na is most metallic among the given elements.

Explanation:

i) We know that as we move across the period from left to right, the atomic size decreases. This is because more number of electrons are added to same shell. This increases the effective nuclear charge . And hence shells are pulled more closer towards the nucleus decreasing atomic size so tendency to loose electron decreases .

Here, we can clearly see that Li comes before than Be in the same period .

Thus, the atom of Li is bigger than Be.

ii) We know that as we move across the period metallic character decreases as net effective nuclear charge increase so atoms are held more tightly by nucleus.

So from the above given information,

since Li and Na are at the first position of their periods thus they both have highest metallic character among the elements of their period respectively.

Also as we move down the group, metallic character increases as electrons are held more loosely by nucleus so the tendency to loose electrons increases.

Here, Na is lower than Li in the same group.

So Na is more metallic than Li.

Hence among the given elements Na has the highest metallic characters.

Answer 2

Answer:

1:- Lithium.

The effective nuclear charge is simply a measure of the net positive charge that affects the outermost electrons in an atom. In lithium's case, the outermost electron is being screened from the nucleus by two core electrons. ... That is why lithium has a larger atomic radius than beryllium.

2:-The most metallic element is francium. However, francium is a man-made element, except for one isotope, and all isotopes are so radioactive they almost instantly decay into another element. The natural element with the highest metallic character is cesium, which is found directly above francium on the periodic table.