Problem 148 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following nuclear reactions will generate an isotope? \([2007]\) (a) positron emission (b) \(\alpha\) particle emission (c) \(\beta\) particle emission (d) neutron particle emission

Step-by-Step Solution

Answer

(d) neutron particle emission

Step 1: Understanding the Problem

We need to determine which type of nuclear reaction will produce an isotope. An isotope is a variation of an element that has the same number of protons (same element) but a different number of neutrons.

Step 2: Positron Emission

In positron emission, a proton in the nucleus is converted to a neutron, releasing a positron. This changes the atomic number but leaves the nucleon (mass) number constant.

Step 3: Alpha Particle Emission

During alpha () particle emission, a nucleus loses 2 protons and 2 neutrons, decreasing the atomic number by 2 and the mass number by 4. This changes the element, not just creates a different isotope.

Step 4: Beta Particle Emission

In beta () particle emission, a neutron in the nucleus transforms into a proton, releasing an electron. This increases the atomic number by 1 but leaves the mass number unchanged. The element changes instead of forming an isotope.

Step 5: Neutron Particle Emission

In neutron emission, a neutron is ejected from the nucleus. The mass number decreases by 1, but the atomic number remains the same, thus forming a different isotope of the original element.

Step 6: Conclusion

From the above analysis, neutron particle emission will generate an isotope because it changes the number of neutrons without altering the atomic number.

Key Concepts

Isotopes

Isotopes are versions of the same chemical element that have identical numbers of protons but different numbers of neutrons. Because they have the same proton number, they are considered the same element.
Atomic number defines an element, which is the number of protons in the nucleus. The mass number, however, includes both protons and neutrons. Isotopes of an element will have the same atomic number but different mass numbers.

• For example, Carbon-12 and Carbon-14 are isotopes of Carbon. Both have 6 protons but Carbon-12 has 6 neutrons and Carbon-14 has 8 neutrons.
• Isotopes can occur naturally or be artificially createdusing nuclear reactions.

Isotopes play significant roles in various fields, such as medicine, archeology (carbon dating), and nuclear energy.

Positron Emission

Positron emission is a type of nuclear reaction where a proton in the nucleus is converted into a neutron. During this process, a positron, which is a particle similar to an electron but with a positive charge, is emitted.
This reaction decreases the atomic number by one because a proton is lost but the mass number remains constant as the total nucleons do not change.

• It's often involved in the transformation of an element into another element and is frequently used in medical imaging techniques such as Positron Emission Tomography (PET scans).
• Unlike neutron emission, positron emission does not result in different isotopes but instead transmutates the element.

Understanding positron emission is helpful in medical applications and the study of particle physics.

Alpha Particle Emission

In alpha particle emission, the nucleus emits an alpha particle, which is essentially a helium nucleus containing two protons and two neutrons.
This results in the loss of 2 protons and 2 neutrons, causing the atomic number to decrease by 2 and the mass number by 4.

• This changes the element itself rather than forming an isotope because the identity of an element is defined by its atomic number.
• For instance, when Uranium-238 undergoes alpha decay, it transforms into Thorium-234, changing from one element to another.

Alpha particle emission is a key concept in understanding radioactive decay and the stability of heavy elements.

Beta Particle Emission

Beta particle emission involves the transformation of a neutron into a proton within the nucleus, with the release of an electron (called a beta particle).
This process increases the atomic number by one but leaves the mass number unchanged since a neutron is converted to a proton without adding a new nucleon.

• This type of emission also changes the element rather than producing a different isotope.
• An example is Carbon-14 decaying into Nitrogen-14 by beta decay, where a neutron in Carbon-14 transforms into a proton, creating Nitrogen.

Beta particle emission is significant in nuclear chemistry and helps explain the processes in radioactive decay chains.