Atoms and Stoichiometry Flashcards
1
Q
Radon’s Decay Proccesses
A
- In the example of the decay of radon, the atom will transition multiple times through being the same elements, including being bismuth, thallium and lead atom multiple times.
- Radon undergoes decay processes until it becomes a stable atom of lead.
- Along the way, it typically becomes two other versions of lead before reaching that final, stable version.
- To be lead, they must have something in common, and thats a positive charge of their nucleus.
- That positive charge comes from the protons, a type of nucleon, which is anything in the nucleus, which could be a proton or neutron.
- Since the protons are what they have in common then the neutrons must be the difference.
2
Q
J.J Thompson
A
- Physicist that discovered the first evidence of atoms of the same elements having different masses.
- To do this, Thompson and his team charged atoms of neon, making them positive ions and removing an electron.
- The ionized neon gas was accelerated down an evacuated tube, and passed through an electromagnet.
- The electromagnet exerted a constant force on all the ions perpendicular to their path of motion, making the stream of ions turn
- At the other end of the tube was a photographic plate
- The discovery Thompson made was that the neon marked two different locations on the photographic plate.
- But all the ions were traveling the same original path and speed, and experience the same force from the electromagnet.
- This means that the turn of the atoms had to have been different.
3
Q
Newton’s Law
A
- Acceleration is proportional to force and inversely proportional to mass.
- F=ma
4
Q
Conservation of Mass
A
- The total number of nucleons must remain constant before and after decay processes
5
Q
Conservation of Charge
A
- The total charge must remain constant before and after the decay process
6
Q
Alpha Decay
A
- This type of decay tends to occur with only heavier elements, larger than nickel
- An alpha particle is emitted
- One way to look at an alpha particle is that its essentially just the nucleus of a typical helium atom
- In alpha decay, a parent nucleus (the atom at the start of the process) emits a helium nucleus. The atomic number of the daughter nucleus (The product nucleus) decreases by 2, and its mass number decreases by 4.
- Nuclear reactions must be balanced for mass number and atomic number
7
Q
Beta Minus Decay
A
- Involve the conversion of a nucleon → a neutron turning into a proton or a proton turning into a neutron.
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Beta minus Decay
- Stable nuclei need to have the right ration of neutrons to protons for the size of the nucleus.
- If the neutron number is too high the nucleus can become more stable by converting one of those neutrons into a proton which is done by the neutron emitting an electron
- While electrons normally want to stick around the nucleus the electrons produced in a beta decay have enough kinetic energy that they fly off.
- Since the atom just gained an electron the atomic number goes up by 1, but the mass number of an electron is 0, so the mass number stays unchanged in beta minus decay.
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Example:
- One of the isotopes produced during the decay sequence from radon is bismuth-214.
- This daughter isotope is unstable, so it will be the parent nucleus for another decay reaction
- The most stable isotope of bismuth is bismuth-209 with 83 protons and 126 neutrons.
- The bismuth produced during radon decay, bismuth-214, has 131 neutrons, five more than is stable
- This makes its dominant form of decay, beta minus decay.
- This will lower the neutron to proton ratio.
- In beta minus(-) decay, a nucleus emits an electron the daughter nucleus’s atomic number drops by 1, but its mass number does not change
8
Q
Beta Plus Decay
A
- In beta-plus decay, rather than a neutron becoming a proton, a proton becomes a neutron, and the nuclear charge drops by 1 and a particle with a positive charge is emitted.
- That particle is a beta-plus particle, also called a positron
- Beta plus decay isn’t actually found in the decay series involving radon.
- Carbon-11 is not a typical form of carbon and only ever exists when we specially synthesize it, and even then it doesn’t last for long.
- With a mass of 11, it has too few neutrons for its number of protons. In order to become stable, one of the protons emits a positron and converts it into a neutron. Mass doesn’t change in any type of bets decay, but the positive charge in the nucleus just decreases by 1, meaning that the atomic number changed from 6 (that or carbon) to 5, making the daughter nucleus boron.
9
Q
Positron
A
- Is the antimatter equivalent of an electron.
- All its properties are the same, except for the charge
- That positron is the “P” in PET scans, which is known as Positron Emission Tomography, which is a technique used to study metabolism.
10
Q
Electron Capture
A
- The unstable nucleus of carbon-11 actually has an interesting alternative to beta-plus decay. In a small percentage of the carbon-11 atoms, they will satisfy their excess positive charge by grabbing an electron instead of emitting a positron.
- This process, electron capture, brings an electron from the inner shell of the atom into the nucleus and combines it with a proton, converting that proton to a neutron.
- The net effect on the nucleus is the same as beta-plus decay, an electron capture is often lumped in with a beta-plus decay as an “also occurs” footnote
10
Q
Electron Capture
A
- The unstable nucleus of carbon-11 actually has an interesting alternative to beta-plus decay. In a small percentage of the carbon-11 atoms, they will satisfy their excess positive charge by grabbing an electron instead of emitting a positron.
- This process, electron capture, brings an electron from the inner shell of the atom into the nucleus and combines it with a proton, converting that proton to a neutron.
- The net effect on the nucleus is the same as beta-plus decay, an electron capture is often lumped in with a beta-plus decay as an “also occurs” footnote
11
Q
Gamma Decay
A
- In gamma (y) decay, a high-energy nucleus emits a photon and drops to a low-energy state. The atomic number and mass number stay the same.
- All of these types of decay can be dangerous to tissue especially if brought into the body by inhaling parent atoms of decay into the lungs.
12
Q
Alpha Particles
A
- Alpha Particles are enormous and they can do a lot of damage inside the body
- Since they are so big they cannot enter the body from the outside.
- The layer of dead skin stop them
13
Q
Beta Particles
A
- Much smaller and can penetrate into the body more easily
- Even though they have more energy their size means they tend to do less damage than alpha particles, but they can still be dangerous when concentrated somewhere like the lungs.
14
Q
Gamma Particles
A
- Are photos with no mass, so they can pass through the body completely.
- Takes 2 feet of metal to stop a gamma particle.
- The effects of gamma particles on the body are fairly similar to those of beta particles, but can be even more widespread due to their ability to pass through the while body
15
Q
Half-Life
A
- Is the time requires for ½ of the original sample to decay
- The time in which half of the atoms of an unstable isotope will decay.
- X’ = x(½n)
- X’ = amount of sample remaining after decay
- x = amount of original sample
- n = number of half-lives
- Exponential Decay (Formula to determine the fraction of an isotrope left)
- N/No = e-λt
- N/No = the fraction of radioactivity remaining
- e=2.71
- λ = 0.693/t1 /2 (0.693 divided by the half life)
- N/No = e-λt
- The half-life graph can be a a straight line by drawing the logarithmic graph.
- The slope of the line is the rate constant lambda for nuclear decay
16
Q
Representative Elements of the Periodic Table
A
- These are the ones on the right and left ends of the periodic table, in groups 1, 2, 13-18
- These are the groups in which we’re filling either s- or p-orbitals.
- The electors added, ass you move to the right are in the valence shell.
- Atoms further on the right of the periodic table pull more on electrons than those on the left
- The pul on electrons can largely be estimated just by counting the numbers of valence electrons more valence electrons tends to mean more pull
24
Q
D and F Blocks
A
- The electrons gained while moving left to right across the periodic table are being added entirely beneath the valence shell
- In the F-block, the subshells that are filling are two layers beneath the valence shell, so the similarity is even greater.
- The top row has the lanthanides, which have partially filled 4f subshells
- virtually all exist in a +3 oxidation state
- Soft silvery metals
- Difficult to seperate
- Known as Alloy - mishmetal
- The bottom row of the f-block has the actinides
- partially filled 5f subshells
- Radioactive in nature (undergo nuclear decay)
- Plutonium is the heaviest one known to exist in nature
