Test: Group-18 Elements - NEET MCQ

C and D are the correct answers.

The correct answer is Option A. 

Valency of an element is defined as its tendency to accept valence electrons.
Since noble gas has completely filled valence (outer) shells, they have the least reactivity.
Hence noble gases are already stable in its elemental form. So its valency is zero.
 

Xenon reacts with fluorine at 873 K and 7 bar to form XeF4. In this reaction, the ratio of Xenon and fluorine required is 1:5

The correct answer is Option B.

Xe has an electronic configuration of 5s²5p⁶
In XeF², there are two bonding pairs and three lone pairs of electrons. So acc. to VSEPR theory, the structure would be trigonal bipyramidal to avoid electron pair repulsions.(sp³d)
In XeF₄, the structure would be square planar. There are four pairs of bonding electrons and two lone pairs in the molecule. The hybridisation would be sp³d²
XeOF₄ has an octahedral geometry due to sp³d² hybridization. One trans position is occupied by a lone pair giving pyramid shape to the molecule.
Thus  XeF₂ has sp³d hybridization.

Cl, O, and N forms Cl₂, O₂ and N₂ respectively to satisfy octet rule but He has noble gas configuration so do not form any compound and exist as monoatomic gas.

The correct answer is option D
Xe forms maximum no. of compounds among noble gases. It forms bonds with oxygen and fluorine.

The correct answer is Option B
Xe forms maximum no. of compounds among noble gases. It forms bonds with oxygen and fluorine.

The amount of energy required to remove an electron from the atom decreases. Ionization potential, thus, decreases down a group. The element with highest ionization potential in the periodic table is Helium (2372.1 kj/mol), while the element with the lowest ionization potential is Caesium (375.7 kj/mol).

The correct answer is Option C. 

Noble gases have completely filled the outer shell/valence shell. Due to this reason they are very stable and do not react with other elements. Hence noble gases are called inert gases means they do not react with other elements to form chemical compounds.
 

The element present in the 18th group (except Helium(He) has the general electronic configuration ns²np⁶. The elements of the 18th group are called noble gas, having 8 electrons in valence shells, and their outer shells are filled with valence electrons, making them very stable.

XeF₂ molecular geometry is linear. It acquires such shape as the lone pairs present around the central atom tend to take up equatorial positions. The bond angle is said to be 180°.

Option C is the correct answer
Mixture of helium and oxygen (density 2) is lighter than air (density 14.4). Hence, it diffuses more rapidly through constricted lung passages.
Mixtures of helium and oxygen are used as life saving mixtures for an asthma patient.

The correct answer is option B
The element which has not yet been reacted with F₂ is Ar.

The correct answer is Option B
The shape of XeF₄​ is square planar. The central Xe atom has 4 bond pairs of electrons and two lone pairs of electrons. It undergoes sp3d2 hybridization which results in octahedral electron geometry and square planar molecular geometry. The two lone pairs are at opposite corners of an octahedron. This minimizes repulsion between them.

The van der Waals force increases with the increase in the size of the atom, and therefore, in general, the boiling and melting points increase from He to Rn. ... Similarly, because of increased dispersion forces, the boiling and melting points of monoatomic noble gases increase from helium to radon.

The correct answer is option D
Outer electronic configuration represents argon ns²,np⁶.
Atomic no. of argon is 18. Its electronic configuration will be
 1s² 2s² 2p⁶ 3s² 3p⁶.
As the outermost shell is full (3s²3p⁶) it is called noble gas.

The correct answer is Option A.

XeF₆+3H₂O→XeO₃+6HF
XeF6 is one of the three binary fluorides formed by the xenon. The complete hydrolysis of XeF₆ produces XeO₃ which is xenon trioxide. This xenon trioxide is highly explosive and acts as a powerful oxidising agent in solution.
 

Complete hydrolysis of XeF₄ and XeF₆ results in the formation of XeO₃.
6XeF₄ + 12 H₂O ----> 2XeO₃ + 4Xe + 3O₂ + 24HF
XeF₆ + 3H₂O ----> XeO₃ + 6HF

The correct answer is Option A.

In XeO3 , Xe undergoes sp3 hybridisation. sp3 is the molecular geometry of XeO2 which is the trigonal pyramidal. The charge distribution on the central atom is asymmetrical making the molecule polar.