Understanding Alpha Decay: A Comprehensive Overview

good morning today our primary objective with this video is to review alpha decay

specifically we'll try to understand what that symbol means and we'll come to understand that during

an alpha decay radiation is emitted and a new element or atom is formed alpha decay occurs as a result of an

unstable nucleus so the real question is when is the mucus of an atom stable or unstable

our secondary objective will be to analyze questions like these polonium-210 is a radioisotope that

undergoes alpha decay and if ingested in large quantities is lethal

fill in the missing atomic numbers for the decay equation so we'll come to understand what this

equation means and how to solve for x and y we'll also be looking at this example

in a hypothetical radioactive series 2199 gbm undergoes three alpha decay processes what is the resulting product

so the first question we'll answer is when is the nucleus of an atom stable or unstable

so here's a nucleus of an atom let's focus on counting the number of neutrons and protons

there's six protons and six neutrons now we know that protons have a positive charge

that means that protons will repel each other this is called an electrostatic force

and so the real question is what keeps a nucleus together well it's not the electrostatic force

because the protons are repelling each other so there must be another force

and this force is called the strong nuclear force or just the strong force

the strong force interacts between neutrons and protons and neutrons and neutrons and protons and protons and is

attractive in nature however it acts at very short distances only within the size of a nucleus

so when is the nucleus of an atom stable or unstable well it has to do with the ratio of the

number of neutrons to the number of protons and it also has to do with the size of

nucleus helium which is very small compared to uranium

so we're going to use this graph to analyze when a nucleus is stable or unstable

notice the x-axis we're applying the number of protons and the y-axis the number of neutrons

i've plotted this line which represents a one-to-one ratio of neutrons to protons

so now we'll look at some general trends for small atoms usually the number of neutrons is equal to the number of

protons and this results in the atom being stable so for example carbon-12 carbon-12 has

six neutrons and 6 protons this is stable but

carbon 14 is unstable it has 8 neutrons compared to only 6 protons

carbon 10 is also unstable it has four neutrons compared to six protons

sodium 23 with 12 neutrons and 11 protons is considered to be stable

but sodium 24 with an extra neutron is considered to be unstable now i highlight the word usually there

because as we can see magnesium 24 25 and magnesium 26 they are all considered to be stable

so a general rule of thumb is when the atom is small the number of neutrons is usually equal

to the number of protons this results in a stable nucleus however as we can see for

magnesium three different isotopes are all considered to be stable

atoms that are larger are stable when the number of neutrons is greater than the number of protons

nickel 58 has 30 neutrons compared to 28 protons and that's considered to be stable

but nickel 63 is considered to be unstable there's just too many neutrons krypton 84 with 48 neutrons compared to

36 protons is considered to be stable but krypton 85 with an extra neutron is considered to be unstable

a nucleus that is unstable will decay which means that the number of protons and number of neutrons will change

when this decay takes place energy is emitted by the nucleus in the form of radiation hence the decay is often

referred to as a radioactive decay so now let's get to the specifics of an alpha decay

typically occur in unstable nuclei that are very large nucleus emits an alpha particle an alpha

particle consists of two protons and two neutrons and is charged

the alpha particle is identical to the helium nucleus with a charge of two plus we know that alpha particles travel a

relatively slow speed and they can be stopped by a sheet of paper

and even air so the symbol we use for alpha particle you can see there's two different

symbols the alpha symbol with the four two or helium with four two

so let's look specifically at the alpha decay of uranium uranium-238 the 92 refers to the number of protons

this is called the atomic number and the 238 is the atomic mass number this is the number of neutrons plus the

number of protons working backwards you can determine that there are 146

neutrons in total so when uranium decays

we end up getting a helium nucleus being ejected or emitted

from the nucleus of the uranium and we end up with something else being

created that something else is a smaller nucleus

and it's called thorium 234 90. so where does this 234 90 come from

well let's focus on these three numbers 238 234 and 4. notice that 238 is 234 plus 4.

notice that the overall atomic mass number must be equal before the decay and after the decay

so in other words 234 plus 4 has to add up to 238 that is common for all alpha decays

now let's focus on these numbers 92 90 and 2. notice that 92 is equal to 90 plus 2.

and so the number of protons is conserved meaning that the number of protons

before the decay have to equal the number of protons after the decay

this is true for any element that undergoes alpha decay

so this is the overall picture one uranium decays after the decay of uranium we have a

helium nucleus which is the alpha particle we have radiation being emitted

and we have a new nucleus being formed thorium in this case we can use an equation to represent this

radiation that is emitted is not usually shown in the equation this equation can also be represented

like this with the alpha symbol instead of the helium symbol two terms that you may come across when

studying this topic uranium-238 is called the parent nucleus and thorium-234 is referred to

as the daughter nucleus all right let's look at our secondary objective

the example here polonium 210 is a radioisotope that undergoes alpha decay and if ingested in large quantities is

lethal fill in the missing atomic numbers for the decay equation

so can you solve for x and y that's the goal of this question please pause the video now

okay hopefully you gave this question a try focusing on these numbers here

we write out the following equation 210 equals x plus 4 or x is equal to 206. and there it is 206.

solving for y we focus on these numbers here 84 equals y plus 2 or y equals 82

and there's our final solution our next example in a hypothetical radioactive series

219.99 gbm undergoes three alpha decay processes what is the product please pause the

video now okay i hope you try this question so this is what the decay equation looks

like 2999 gbm on the left side

we have three helium or alpha particles on the right side of the equation

and we have this mystery product called db we don't know what the x and y are

we could rewrite it like this just to make the math a little easier and now focusing on those numbers there

we write 219 equals 4 plus 4 plus 4 plus x or 12 plus x

x is 207 so it looks like the answer could be a but we have to complete

our analysis fully focusing on these numbers here 99 equals 2 plus 2 plus 2 plus y

or y equals 93. and so there's our final answer and as you can see none of the answers

correspond to this finally the last part of this video i want to talk about one common

element called americium-241 it is radioactive it undergoes alpha

decay as you can see from the equation and this is commonly found in ionization smoke detectors in your home

so if you have a smoke detector there may be a chance that it has americium-241 in it

i hope you enjoyed today's video have a great day bye bye