Chapter 5: Periodic Classifications of Elements

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Q
Periodic Classifications of Elements

Question:

Which element has:

(a) two shells, both of which are completely filled with electrons?

(b) the electronic configuration 2, 8, 2?

(c) a total of three shells, with four electrons in its valence shell?

(d) a total of two shells with three electrons in its valence shell?

(e) twice as many electrons in its second shell as in its first shell?

Answer:

(a)- The element has two shells only, which means that it has only K and L shell. K shell can accommodate 2 electrons while L shell can accommodate 8 electrons. So, the electronic configuration of this element will be (2, 8). The atomic number of this element is 10. It is neon that belongs to group 18.

Therefore, the name of the element is Neon.

(b)- The element has three electronic shells (K, L, and M). This means that it belongs to the third period. The atomic number of the given element is 12. It is magnesium that belongs to group 2.

Therefore, the name of the element is Magnesium.

(c)- The element has four shells only, which means that it has only K, L, and M shell. K shell can accommodate 2 electrons while L shell can accommodate 8 electrons. The M-shell is the valance shell that has 4 electrons. So, the electronic configuration of this element will be (2, 8, 4). The atomic number of this element is 14. It is silicon that belongs to group 14.

Therefore, the name of the element is Silicon.

(d)- The element has two shells only, which means that it has only K and L shell. K shell can accommodate 2 electrons while L shell is the valence shell that has 3 electrons. So, the electronic configuration of this element will be (2, 3). The atomic number of this element is 5. It is boron that belongs to group 13.

Therefore, the name of the element is Boron.

(e)- The element has two shells only, which means that it has only K and L shell. K shell can accommodate 2 electrons while L shell is the valance shell that has twice many electrons as in the first shell. So, the electronic configuration of this element will be (2, 4). The atomic number of this element is 6. It is carbon that belongs to group 14.

Therefore, the name of the element is Carbon.


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