Question Video: Identifying the Explanation for Why Helium Does Not Form Chemical Bonds | Nagwa Question Video: Identifying the Explanation for Why Helium Does Not Form Chemical Bonds | Nagwa

Question Video: Identifying the Explanation for Why Helium Does Not Form Chemical Bonds Chemistry • Second Year of Secondary School

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The Lewis structure for an atom of helium is shown. Which of these statements explains why helium does not usually form chemical bonds? [A] Helium is too small to form chemical bonds with atoms of other elements. [B] The first electron shell can only hold two electrons; therefore, helium has a full valence shell. [C] Helium changes into hydrogen when it loses one of its electrons. [D] The first electron shell can hold eight electrons, but finding six electrons for a full valence shell is too difficult. [E] Helium is a gas and therefore cannot lose its two electrons.

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Video Transcript

The Lewis structure for an atom of helium is shown below. Which of these statements explains why helium does not usually form chemical bonds? (A) Helium is too small to form chemical bonds with atoms of other elements. (B) The first electron shell can only hold two electrons; therefore, helium has a full valence shell. (C) Helium changes into hydrogen when it loses one of its electrons. (D) The first electron shell can hold eight electrons, but finding six electrons for a full valence shell is too difficult. (E) Helium is a gas and therefore cannot lose its two electrons.

The question asks us about helium. Helium is one of, perhaps the most, unreactive element on the periodic table. It is very small and lightweight and is known as one of the noble gases. An atom of helium has two protons in its nucleus and two electrons in its first electron shell.

Because the first electron shell can hold a maximum of two electrons, we say helium’s valence shell is full. And this is why helium is so unreactive. And it is why helium does not usually form chemical bonds with atoms of other elements. We say “usually” because under extreme conditions, helium may be induced to react, for example, in stars or in special conditions in the laboratory. But in general, helium is considered unreactive, again because it has a full valence shell.

Helium exhibits no need to accept or donate electrons to other atoms in order to form a full valence shell. We could define this relationship. A full valence shell makes an atom unreactive. Other elements which do react do so to obtain a full valence shell and therefore to become stable, just like the noble gases. From this understanding, we can deduce that the correct answer to this question is (B).

Why does helium not usually form chemical bonds? The answer is (B). The first electron shell can only hold two electrons; therefore, helium has a full valence shell.

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