Radioactive Decay, Nuclear Reactions

Half life

A measurement of rate of radioactive decay and nuclear stability

A) Charge of beta decay B) Effects of an beta decay on atomic mass and number

A) negative and B) atomic mass unchanged and atomic number up by 1

A) Charge of alpha decay B) Effects of an alpha decay on atomic mass and number

A) positive and B) atomic mass down by 4 atomic number down by 2

Ion

Electrically charged atom

The SPLITTING of a heavy nucleus into 2 lighter nuclei

Fission

The COMBINING of 2 lighter nuclei to form a heavier nucleus

Fusion

Beta Decay

Neutron breaks in to Proton plus Electron which escapes and can pass thru aluminum foil

As the number of half lives increase, what happens to the number of undecayed nuclei

The amount of undecayed nuclei will decrease

A 6.95 gram sample of radioactive nobelium-259 has a half-life of 58 min. How much is left after 2 hours and 54 minutes?

.869 g

If 1/8 of the original sample is left, how many half lives did it take?

1/2 X 1/2 X 1/2= 1/8 therefore 3 half lives

If a substance has a half-life of 5 years, then how much of the initial sample remains after 15 years?

1/8

How long does a sample of 236 Pb with t1/2 = 3 years take to 6.25% of its original mass?

100-50-25-12.5-6.25 4 half lives

85 83 84 82 81 At Bi Po Pb Tl 210 206 206 202 202 How many alpha & beta?

2 alpha & 2 beta

218/84 Po --> 4/2 He + ?

214/82 Pb alpha decay

226/88 Ra undergoes beta decay to make

226/89 Ac

If an element has a half life of 12 days and a starting mass of 250 g , how much of the sample will be left in 48 days?What fraction will be left?

48 days is 4 half lives so 100-50-25-12.5-6.25 so 6.25% 6.25% of 250 g is 15.63 g left or 1/2 X 1/2 X 1/2 X 1/2 = 1/16 fraction left

209/84 Po ---> 205/82 Pb What type of decay is this?

Alpha

Transuranic elements

Atomic number 92 or higher

Isotope

Atoms of the same element which have different masses

What decay results in a transmuted element with the same atomic mass and an increased atomic #?

Beta

Nuclear fission

Happens in nature. Breaks down atom to smaller pieces creating a more stable nucleus

Nuclear fusion

Happens in the Sun to create larger atoms H + H =He

Isotopes are atoms of the same element that differ in their number of

Neutrons

Why does radioactive decay occur?

The nucleus is larger than the nuclear force can keep stable

Alpha Decay

The release of a 4/2 He and can pass thru paper

Gamma Decay

The release of energy to create a more stable atom in a lower energy state and can pass thru lead

When an element undergoes radioactive decay and a new element is created, the new element is ?

Transmuted element

Transmutation

When decay results in the creation of a new atom

Mass of an electron

almost zero amu