Question

Out of following elements, which element has zero valency?
(a) Na (b) Mg (c) Ar (d) C​

Answer 1

$\fbox\blue{ Ar (Argon}$

Argon (Ar) has zero valency because they have their outer shell completely filled and are chemically inert gas.

Additional Information –

• It is discovered by Sir William Ramsay and Lord Rayleigh in 1894.

• Argon was discovered by taking away air and was left with the substance stronger the nitrogen.

• Argon is a gaseous chemical element which makes up almost one percent Earth's Atmosphere.

• It is used for wielding in light bulbs, and for growing crystals.

Hope it helps you.

Answer 2

• Valency is the Combining Capacity of an Element.

• Electrons in the outermost shell will determine the valency of that Element.

• In order to become stable, Elements need 8 electrons. In other words, an Element is stable if its octet is complete in the outermost valence shell.

• If an Element has its octet complete in the natural occurrence state, then such elements are called 'Inert Elements' because they do not react with any other elements. They already have their octet complete.

Example: Argon (Ar) has 8 electrons in its outermost valence shell and so does not give, take or share electrons with other elements. Such Elements have 0 valency.

• If the number of Electrons in the Outermost shell is 1, 2 or 3; then the Element has tendency to give away those unstable Electrons and become stable. Such Elements are called 'Electro-Positive Elements.' This is because, Protons will be more than Electrons after giving away unstable Electrons. Such Elements form 'Ionic Bonds.'

Example:

Sodium (Na) has 1 electron in its valence shell. So, It gives-away that 1 electron to become a Na⁺ ion. Its valency is +1

Magnesium (Mg) has 2 electrons in its outermost valence shell. So, it gives away that 2 electrons to become Mg²⁺ ion. Its Valency is +2

• If the number of Electrons in the outermost shell is 4; then the Atom has to either accept 4 electrons or give-away 4 electrons to become stable. In such a case, the Element chooses to share its 4 electrons with another elements to complete its octet. Such Elements form 'Covalent Bonds.'

Example: Carbon (C) has 4 electrons in its outermost valence shell. So, It shares its 4 electrons with another carbon atom or other elements to form Covalent bonds. Thus, Valency of Carbon is ±4.

• If the number of Electrons in the outermost shell is greater than 4, then the Element will accept Electrons to complete its octet and become stable. Such elements are called 'Electro-Negative Elements.' This is because Electrons will be more than Protons after accepting additional Electrons. Such Elements form 'Ionic Bonds.'