Atomic Radii Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. Atomic radius depends upon

1. anionic nature
2. cation nature
3. nature of bonding
4. metallic nature

Ans. The correct answer is c. nature of bonding

Explanation: The covalent radius needs to be taken into consideration for nonmetals. Also, metallic radius for metals and a van der Waals radius for noble gases. Thus, the atomic radius depends on the nature of the bonding.

Ques. The atomic radius of a hydrogen atom is

1. 63 pm
2. 46 pm
3. 28 pm
4. 53 pm

Ans. The correct answer is d. 53 pm

Explanation: Atomic radius is the distance between the center of the nucleus and the outermost boundary of the electrons that surround it. The atomic number of hydrogen is 1 and its standard atomic weight is 1.008. It has an atomic radius of 53 pm, where pm stands for picometer measurement.

Ques. Atomic radius is measured by

1. Rutherfords ɑ-ray scattering experiment
2. Millikan's oil drop method
3. X-ray diffraction technique
4. Thomson's water-melon model

Ans. The correct answer is c. X-ray diffraction technique

Explanation: The atomic radius of an atom is the distance between the nucleus's center and the atom's outermost shell containing electrons, known as the valence shell. Atomic radius can be calculated using X-ray diffraction or other spectroscopic techniques.

Ques. Is it possible to measure atomic radius directly?

Ans. The atomic radius cannot be determined directly due to uncertainty in the exact position of the outermost electron.

Ques. Does atomic number increase across a period table?

Ans. For certain periods, the size of an atom decreases as we go from left to right. As a result, the atomic radius decreases across a period while increasing down a group.

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Short Answers Questions [2 Marks Questions]

Ques. Among S, Se, P, and As, which element will have the largest atomic radius?

Ans. In a periodic table, the atomic radius increases as we move down and there is a decrease in the atomic radius if we move from left to right. Arsenic and Selenium are located at the lowermost row of the periodic table but arsenic is more to the left. Therefore, As has the largest atomic radius.

Ques. Among P, Bi, N, and As, which element will have the smallest atomic radius?

Ans. The elements mentioned above are in the same groups in the periodic table, and we know that the atomic radius increases from top to bottom. Moving along the group adds another shell, resulting in an increase in atomic size. As a result, Nitrogen has the lowest atomic size in this case.

Ques. Define Van Der Waals radius.

Ans. It is defined as half the distance between the nuclei of two isolated non-bonded comparable atoms, as well as two adjacent identical atoms belonging to nearby atoms in the solid state. These are held together by a weak magnitude force known as the van der Waal force. The ionic radius of chlorine in an ionic state is 360 pm and the Vanderwall radius of the chlorine atom is said to be 180 pm.

Ques. Which element in the periodic table is said to have the largest atomic radius?

Ans. FRANCIUM is the element in the first group and the seventh row is said to have the largest atomic radius. Francium has an atomic number 87 and is a chemical element with the symbol Fr. It is extremely radioactive; the half-life of its most stable isotope, francium-223, is just 22 minutes. It is the second most electropositive element, after cesium, and the second rarest naturally occurring element.

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Long Answers Questions [3 Marks Questions]

Ques. What is the ionic radius?

Ans. The radius of the atom that makes ionic bonding is known as the ionic radius. Atomic bonds restrict electrons and nuclei, which leads to no definite shapes for atoms and ions. The ionic radius is measured in Angstrom (A₀) or picometer (pm) units. An ionic atom's radius typically ranges from 30 to 200 picometers.

Ques. What is meant by Bohr Radius?

Ans. The radius of the lowest-energy electron orbit was predicted by the Bohr model of the atom. It is a physical constant that describes the most probable distance between the electron and the nucleus in the ground state of a hydrogen atom. It is denoted by ao or r0. It takes its name from the Danish scientist Niels Bohr.

Ques. Why is the Van der Waals Radius always greater than the Covalent Radius?

Ans. The attraction forces of Van der Waals are modest. As a result, the internuclear distance between atoms bound together by Van der Waal forces is considerably more than the distance between covalently connected atoms. Because a covalent bond is formed by the overlap of two half-filled atomic orbitals, a portion of the electron cloud is shared. As a result, covalent radii are usually lower than van der Waal radii.

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Very Long Answers Questions [5 Marks Questions]

Ques. Explain how atomic radii are a periodic property.

Ans. Due to the reasons mentioned below, atomic radii are a periodic property

• Variation in a group: The atomic radius of elements increases as we move from top to bottom in a group as the atomic number increases. The nucleus's attraction to electrons decreases as the shell number increases. As a result, the atomic radius increases along with the group.

• Variation in periods: When we move from left to right in a period, the atomic radius decreases. Moving left to right in a period, the nuclear charge rises by one unit in each element that follows. However, the number of shells remains constant, causing electrons to be strongly attracted to the nucleus and the atomic radius decreases along with the period.

Ques. What do you mean by covalent radius?

Ans. The radius of an atom that is in a covalent bond with another atom is defined as the covalent radius. 

• Another method of calculating covalent radius is to measure the bond lengths of covalently bonded atoms. 
• When two atoms of the identical type are joined, the covalent radius is half the bond length. 
• Covalent radius may be easily determined in certain chlorine and oxygen molecules by measuring half of the bond length. 
• Half of the internuclear distance between two bound atoms is naturally classified as covalent.

Ques. Calculate the radius of the third orbit of a hydrogen atom. Compare it with the radius of the second Bohr’s orbit of a singly ionized helium atom.

Ans. The radius of the n^th orbit of a hydrogen atom is given by

r_n = n²r₀

Where

• n is the number of orbits
• r₀ is Bohr’s radius = 5.3 x 10^-11 m

For the third orbit, n = 3

⇒ r₃ = 32 x 5.3 x 10^-11 = 4.77 x 10^-10 m = 4.77 Å

Now, the radius of radius of the nth orbit of a singly ionized helium atom is given by

(r_n)_He = n²r₀ / z

Here z = 2 is the atomic number of the helium atom

For the second orbit, n = 2

⇒ (r₂)_He = (22 x 5.3 x 10^-11) / 2 = 1.06 Å

Therefore the ratio of the radius of the third orbit of a hydrogen atom and the radius of the second orbit of a singly ionized helium atom is given by

r₃ / (r₂)_He = 4.77 / 1.06 = 4.5

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