Question

Calcium is an element with the atomic number 20.
I. Will it be metal or nonmetal?
II. What will be its valency?
III. What would be the formula of its chloride?
IV. Will it be smaller or larger than potassium?

Answer 1

Hint: Try to recall that calcium is an element of group-2 on modern periodic table and it has a tendency to lose electrons in order to acquire the nearest noble gas electronic configuration. Now, by using this you can easily answer all the above given questions.

Complete step by step solution:
It is known to you that calcium has 20 electrons and the electronic configuration of calcium is 2, 8, 8, 2.
I. Since, the number of electrons in the valence shell of calcium is 2 so it will lose these two electrons and acquire the stable electronic configuration of argon. So, calcium will be a metal as it has a tendency to lose electrons.
II. We know that valency of an element is the number of electrons gained or loose in order to acquire stable noble gas electronic configuration. So, the valency of calcium will be 2.
III. We know that calcium will lose two electrons to form ion $Ca^{2+}$ so, the formula of its chloride is \[CaC{l_2}\].
IV. We know that on going from left to right along a period on the modern periodic table, the elements tend to decrease in size and also, it is known that both potassium and calcium belong to the same period and potassium lies to the left of calcium So potassium will be larger than calcium.

Note:
* It should be remembered to you that calcium is used in the extraction of metals from their oxides which are difficult to reduce with carbon.
* Also, you should remember that calcium metal due to its reactivity towards oxygen and temperature at elevated temperatures has often been used to remove last traces of air from vacuum tubes.