Write a balanced equation for each of the following nuclear reactions: (a) mercury-180 decays in

Write a balanced equation for each of the following nuclear...

Key Concepts

Alpha Decay

Alpha decay is a type of radioactive decay where an unstable nucleus emits an alpha particle, which is essentially a helium-4 nucleus (two protons and two neutrons). This process reduces both the atomic number and mass number of the original nucleus in a fixed relation, making it straightforward to balance the resulting nuclear equation.

Beta Decay

Beta decay involves the transformation of a neutron into a proton with the emission of an electron (beta-minus decay) or a proton into a neutron with the emission of a positron (beta-plus decay). This decay mode changes the atomic number by one while leaving the mass number unchanged. It is essential for balancing nuclear equations where the identity of the element changes with little or no change in mass number.

Neutron Capture

Neutron capture is a nuclear reaction in which a nucleus absorbs a free neutron, often followed by a beta decay process. The absorption increases the mass number by one while the subsequent beta decay alters the atomic number. This sequential process is key in understanding how heavier isotopes are formed in nuclear reactions and must be accurately represented in balanced nuclear equations.

Nuclear Reaction Balancing

Nuclear reaction balancing is based on the conservation laws of atomic number and mass number, ensuring that the number of protons and neutrons remains constant before and after the reaction. This concept is critical in writing balanced nuclear equations where the sum of the atomic numbers and mass numbers on the reactant side equals that of the products.

Transcript

00:01 In this question, we're asked to go through a series of nuclear reactions and ensure that they're balanced properly.

00:11 So the first example, we're asked to take a look at, tells us that we have mercury 180.

00:18 So it doesn't give us the atomic number, so we need to look that up on the periodic table.

00:22 Atomic number for mercury is 80.

00:24 And it does tell us that it produces platinum 176.

00:29 So again, looking up the atomic number for platinum shows 78.

00:34 And some other particle needs to have been emitted here to keep the mass numbers and atomic numbers balanced on both sides of the nuclear reaction.

00:45 So we need a particle that gives us a value of four for the mass number and a value of two for the atomic number.

00:54 Because when we add 4 to 176, we're going to get the 180 balance of mass numbers on the left and right side.

01:02 And when we add 2 to 78, we're going to get the 80 for the atomic number balance on the left and right side of the equation.

01:11 So what particle is that? that's an alpha particle.

01:14 So an alpha particle or a helium nucleus will give us two in terms of two protons and four in terms of our mass.

01:25 Number and that's our missing particle here the alpha particle or the helium nucleus is the other product of this reaction we're given in this case of question b we don't know our starting reactant but we do know this that an electron or sometimes referred to as a beta negative particle kind of treated in the same way.

01:58 Again, those are kind of used interchangeably.

02:00 And we'll see that again down here.

02:04 And zirconium 90 produced in the reaction.

02:07 So again, look up the atomic number for zirconium and it's 40.

02:12 So in order to keep everything balanced, right, the beta particle or the electron doesn't add anything to the mass number.

02:21 So we know the mass number of a missing reagent here must be 90 and we know that the atomic numbers have to balance the negative one plus the 40 from zirconium has to give us a 39 and now all we have to do is look up element number 39 good old yittrium has to be our missing reagent here in helping us keep everything balance between mass number and atomic number for the balanced nuclear reaction in question b now question c is a chain reaction essentially.

02:59 It says we're going to start with uranium 238...

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