nuclear chemistry

%%nucleus review:%%

- %%atomic nuclei%% are made up of positively charged protons and neutral neutrons

- # of protons determines the element

- %%isotopes%% are atoms of the same element with different # of neutrons

- nuclear chemistry is chemistry that deals with changes to the nucleus of atoms

- this is the very first type of “%%reaction%%” that we will deal with

%%stability of nuclei:%%

- not all atomic nuclei are stable, meaning that they cannot exist forever when left undisturbed

the full explanation why deals with some extremely complicated physics (%%short answer: stability = minimal amount of energy, instability = not yet at minimum%%)

- an unstable nucleus is %%radioactive%%—it releases energy by emitting high-speed particles (%%radiation%%)

- any isotope of an element that has an unstable nucleus/is radioactive is known as a %%radioisotope%%

type 1: very heavy elements—any element above 82 is radioactive

type 2: bad ratio of protons and neutrons

chemical vs. nuclear rxns:

1. chemical

- rearrange atoms (%%share & transfer e-%%)

- the nucleus is unchanged

- 2(H2) + O2 → 2(H2)O

- affected by the changes in T, P, or catalysts

2. nuclear

- change 1 element into another transmutation

- the nucleus is changed

- not affected by the changes in T, P, or catalyst

REFERENCE: TABLE O

%%natural decay:%%

before/parent nucleus → after/daughter nucleus

natural decay: alpha (α)

speed - slow

mass - 4 amu

charge - +2

%%α-particle = 4/2 He (emission)%%

natural decay: beta (β-)

speed - medium

mass - 0 amu

charge - -1

%%β--particle = 0/-1 e (emission)%%

natural decay: positron (β+)

speed - medium

mass - 0 amu

charge - +1

%%β+ - particle = 0/+1 e (emission)%%

natural decay: gamma (γ)

speed - fast

mass - 0 amu

charge - 0

penetrating powers rank (increasing):

1. alpha
2. beta
3. gamma
4. neutron

using table n: shows natural decay processes of several radioisotopes

- radioactive decay is the process by which an %%unstable atom loses energy%% via radiation

- natural decay—naturally occurring, not human-induced

important information about natural decay:

- there is always going to be one reactant (starting material)—%%the original radioisotope%%

- there will always be two products—%%the emitted particle and the new isotope%%

- mass and charge must balance out

finding radioactive decay products:

1. determine what type of decay the given isotope undergoes

alpha: loses 2n and 2p

beta-: 1n becomes 1p

beta+: 1p becomes 1n

2. identify the %%radioisotope%% and %%all necessary atomic information (mass number, atomic number)%%
3. apply the change from the proper decay type
4. show the change with proper notation

(reactant) → (product 1) + (product 2)

%%half-life:%%

can we calculate when a radioactive atom decays?

we can’t, you can’t influence radioactive decay by changing the conditions surrounding an atom, and it is entirely random

- our best guess is to measure a sample of radioactive atoms to determine how long it takes for half of the atoms in them to decay into the product

- this is the half-life of a radioactive isotope—the amount of time it takes on average for half of the atoms in a sample to radioactively decay

%%transmutations:%% atoms of one element changing to atoms of a different element

two kinds: natural & artificial

natural - happens spontaneously, radioactive decay, 1 reactant

ex.: uranium-238 → thorium-234 + alpha particle

artificial - requires shooting particles at another particle, 2 reactants

some general physics knowledge:

E = mc^2

E = energy

m = mass

c = the speed of light

(this equation tells us that mass could be converted to energy)