What are Isobars Questions

In chemistry, an isobar is any member of a group of atomic or nuclear species that all have the same mass number, i.e. the same total number of protons and neutrons.

What are Isobars Chemistry Questions with Solutions

Q-1: The isobars among the following is

1. ⁴⁰Ca₂₀ and ²³Na₁₁
2. ¹⁵⁰Sm₆₂ and ¹⁵⁰Eu₆₃
3. ⁹⁸Tc₄₃ and ⁹⁹Tc₄₃
4. ¹²⁹Te₅₂ and ¹²⁸Sb₅₁

Answer: b)¹⁵⁰Sm₆₂ and ¹⁵⁰Eu₆₃

Explanation: Because the mass number of ¹⁵⁰Sm₆₂ and ¹⁵⁰Eu₆₃ are the same, these element pairs are isobars.

Q-2: Consider the atoms ¹⁶O,¹⁸O, ¹⁸F, ¹⁸Ne and ²⁰Ne. Answer the following:

a) Which atoms are isobars?

b) Which atoms are isotopes?

c) Do isobars have the same/different physical properties?

d) Which have the same number of neutrons?

e) Which atoms have the same number of valence electrons?

Answer:

a) ¹⁸O, ¹⁸F and ¹⁸Ne

b) ¹⁶O and¹⁸O are isotopes

¹⁸Ne and ²⁰Ne are isotopes

c) Isobars have the same physical properties.

d)

From the table it is concluded that ¹⁶O and ¹⁸Ne have the same number of neutrons. Also ²⁰Ne and ¹⁸O have the same number of neutrons.

e) ¹⁶O and ¹⁸O have the same valence electrons.

¹⁸Ne and ²⁰Ne have the same number of valence electrons.

Q-3: Select the isotopes, isobars, and isotones from the following list of atoms.

¹³¹₅₄Xe, ¹³⁰₅₃I, ¹³²₅₅Cs, ¹³¹₅₃I

Answer:

Isotopes: ¹³⁰₅₃I and ¹³¹₅₃I

Isobars:¹³¹₅₄Xe and ¹³¹₅₃I

The species which have the same number of neutrons are called isotones.

Number of neutrons of ¹³¹₅₄Xe= 77

Number of neutrons of ¹³⁰₅₃I = 77

Number of neutrons of ¹³²₅₅Cs= 77

Number of neutrons of ¹³¹₅₃I = 78

Isotones:¹³¹₅₄Xe,¹³⁰₅₃I,¹³²₅₅Cs

Q-4: Write the electronic configuration of any one pair of isobars.

Answer:²⁴₁₁Na and ₁₂²⁴Mg is one pair of isobar. Their electronic configuration is given below:

²⁴₁₁Na: 1s²2s²2p⁶3s¹

₁₂²⁴Mg: 1s²2s²2p⁶3s²

Q-5: Composition of the nuclei of two atomic species A and B is given below:

Give the mass numbers of A and B. What is the relation between two species and which element or elements they represent?

Answer: Mass number is the sum of protons and neutrons in an atom.

Mass number of A = 18+22 = 40

Mass number of B = 20+20= 40

Because they both have the same mass number, they are isobars.

Atomic number of A = number of protons in A = 18

Atomic number of B = number of protons in B= 20

Referring to the periodic table, Element A is Argon and Element B is Calcium.

Q-6: Determine the pair of isobars from the table below.

Answer: K and M

Explanation:

Because the atoms K and M have the same mass number, they are isobars.

Q-7: Isobar of an element have

a) the same number of neutrons but different atomic masses

b) same number of nucleons but different protons

c) same number of nucleons and protons

d) same number of neutrons

Answer: b) same number of nucleons but different protons

Q-8: State which of the following statements is true.If False, state a reason.

Statement 1: The atoms of different elements having the same mass number but different atomic number are known as isobars.

Statement 2: Neutrons and protons are present in the nucleus and their sum is different for isobars.

Answer: Statement 1 is true but statement 2 is false.

Explanation: Statement 2 is false because the sum of protons and neutrons is called mass number which is the same for isobars.

Q-9: Select the correct adsorption isobars for chemisorption and physisorption respectively:

Here, x/m = degree of adsorption)

Answer: c)

Explanation: The adsorption isobar is a plot of the amount adsorbed versus the temperature (T) of the adsorbate at constant pressure.In the case of chemisorption, there is an initial increase and then a decrease, whereas in the case of physisorption, there is a consistent decrease as temperature increases.

Thus, c) is the correct adsorption isobars for chemisorption and physisorption respectively.

Q-10: Determine which pairs are not isobars.

a) ₆¹²X, ₆¹³Y

b) ₁₇³⁵X, ₁₇³⁷Y

c) ₄⁸X, ₅⁸Y

d) ₆¹⁴X, ₇¹⁴Y

Answer: a) and b)

Explanation: Since ₆¹²X, ₆¹³Y and ₁₇³⁵X, ₁₇³⁷Y have different mass numbers, therefore they are not isobars.

Q-11: Which theory states that ‘Atoms of different elements may have the same atomic mass’?

a) Berzelius Hypothesis

b) Modern Atomic Theory

c) Avogadro’s Hypothesis

d) Maxwell theory

Answer: b) Modern Atomic Theory

Q-12: For the isobars ₂₇⁶⁴ Co and ₂₈⁶⁴Ni, answer the following questions:

a) Find the number of d-electrons

b) To which group and period, do they belong to?

Answers:

a) For ₂₇⁶⁴ Co, the electronic configuration is [Ar] 3d⁷4s²_. Thus, the total number of valence electrons is equal to 9.

For ₂₈⁶⁴Ni, the electronic configuration is [Ar] 3d⁸4s²_. Thus, the total number of valence electrons is equal to 10.

b) ₂₇⁶⁴ Co: Period-3, group-27

₂₈⁶⁴Ni : Period-3, group-28

Q-13: How are isodiaphers different from isobars in chemistry?

Answer: Isodiaphers are a pair of nuclides with the same difference in the number of protons and neutrons in their nucleus. Both nuclides have different numbers of protons and neutrons in their nuclei, but the difference is the same.

For example: Uranium ²³⁸₉₂U and Thorium, ²³⁴₉₀Th

Uranium’s nucleus contains 92 protons and 146 neutrons, so the difference is: 146 – 92 = 54.

Thorium’s nucleus contains 90 protons and 144 neutrons, so the difference is 144 – 90 = 54

On the other hand, isobars have the same sum of protons and neutrons in their nucleus.

Q-14: Which pair of neutrons and protons correspond to the isobar of N and C which have a mass number of 14?

a) N: 7 protons and 7 neutrons ; C: 8 protons and 6 neutrons

b) N: 6 protons and 8 neutrons ; C: 8 protons and 6 neutrons

c) N: 6 protons and 8 neutrons ; C: 6 protons and 8 neutrons

d) N: 7 protons and 7 neutrons ; C: 6 protons and 8 neutrons

Answer: d) N: 7 protons and 7 neutrons ; C: 6 protons and 8 neutrons

Q-15: Give the electronic configuration for the following isobars?

a) ⁴⁰₁₈Ar

b) ⁴⁰₁₉K

c) ₂₀⁴⁰Ca

Answer:

Practise Questions on What are Isobars

Q-1: Give answers of the questions based on the given table:

a) What is the atomic number of the sample C and D?

b) Which pair of elements are isobars?

c) What is the valency of Sample B?

d) What type of ion will sample A will form?

Q-2: Given below are some of the very stable or very long lived nuclei: ⁵⁸Fe,⁶⁰Fe,⁶²Fe, ⁶⁰Co, ⁵⁸Ni,⁶⁰Ni,⁶²Ni.

Answer the following questions:

a) Which two nuclei are isotopes of ⁶²Fe?

b) Which two nuclei are isobars of ⁶⁰Co?

Q-3: Which of the following statement(s) is/are correct?

a) Isotones are atoms of the same elements having the same number of neutrons.

b) Isobars are the atoms of the same elements having the same mass number.

c) Isobars are the atoms of the different elements having the same mass number.

d) Isotones and Isobars both are atoms of different elements.

Q-4: The table given below shows the mass number and the atomic number of certain elements A, B and C. Study the given data and answer the following questions:

a) Which element is a f-block element and p-block element?

b) Which two elements are isobars?

Q-5: X and Y are two elements with the same mass number but different atomic numbers 27 and 30 respectively. If X has a mass number of 57, the number of neutrons in Y is

a) 30

b) 27

c) 33

d) 40

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