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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.

Definition: Isobars are atoms with the same number of nucleons from different chemical elements.

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)

Atoms

Mass number

Atomic number

Number of neutrons= Mass number-Atomic number

16O

16

8

8

18O

18

8

10

18F

18

9

9

18Ne

18

10

8

20Ne

20

10

10

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:

A

B

Protons

18

20

Neutrons

22

20

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.

Atoms

Number of neutrons

Number of protons

K

X-1

Y+3

L

X+2

Y-1

M

X

Y+2

N

X+3

Y-4

Answer: K and M

Explanation:

Atoms

Number of neutrons

Number of protons

Mass number

K

X-1

Y+3

X+Y+2

L

X+2

Y-1

X+Y+1

M

X

Y+2

X+Y+2

N

X+3

Y-4

X+Y-1

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)

Adsorption isobars

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:

Elements

Number of electrons

Electronic configuration

K L M N

4018Ar

18

2 8 8

4019K

19

2 8 8 1

2040Ca

20

2 8 8 2

Practise Questions on What are Isobars

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

Element

Number of protons

Number of electrons

Number of neutrons

A

17

20

17

B

17

18

17

C

20

18

20

D

18

19

18

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:

Elements

Mass number

Atomic number

A

12

6

B

154

66

C

154

65

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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