Question

The atomic number of an element is 20. (a) Write its electronic configuration and determine its valency. (b) Is it a metal or a non-metal ? (c) Write the formula of its chloride. (d) Is it more reactive or less reactive than Mg (atomic number 12) ? Give reason for your answer.

Answer 1

The element is calcium(Ca)

(a)2,8,8,2 or $1s^{2} 2s^{2} 2p^{6} 3s^{2}3p^{6}4s^{2}$

(b)It is a metal

(c)$CaCl_{2}$

(d)calcium is more reactive than magnesium since it has another shell which means it's easier for calcium to lose electrons, in other words, calcium is more electropositive than magnesium

Answer 2

(a)  Electronic configuration of calcium is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$ and its valency is 2.

(b)  It is a metal.

(c)  Formula of its chloride is $CaCl_{2}$.

(d)  It is more reactive than magnesium.

Explanation:

• Atomic number of calcium is 20 and its electronic distribution is 2, 8, 8, 2. Therefore, electronic configuration of calcium is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$.

• As it contains only 2 valence electrons this means that it belongs to group 2 of the periodic table. Therefore, it is a group 2 element which are also known as alkaline earth metals. Hence, calcium is a metal.

• As we move down the group size of elements increases and therefore, their reactivity also increases because force of attraction between the nucleus and valence electrons decreases. As a result, metals can easily lose electrons.

• Therefore, calcium is more reactive than magnesium. And, formula of its chloride is $CaCl_{2}$.

Learn more about electronic configuration:

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Learn more about reactivity of metals:

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