Nuclear Chemistry

ATOMIC REVIEW:•Atomic number

= # of protons•# of neutrons

= mass # - atomic #•protons & neutrons are in the

nucleus

ATOMIC REVIEW:•isotopes have different # of

neutrons•there are 3 forms of isotope

notation

carbon-12 C126 C1

2

• Nucleon = term for all protons & neutrons• Strong nuclear force • short-range force among nucleons

– Increases with shorter distance– NOT the same as an electric force

• isotopes have different # of neutrons

• there are 3 forms of isotope notation

ATOMIC STRUCTURE

carbon-12 C126 C1

2

Stable vs. Unstable

•Stable nucleino spontaneous changes

•Unstable nucleispontaneously changes to become a nucleus of a different element

Transmutation•Unstable nuclei are naturally

“built wrong” and “fall apart”•An unstable nucleus undergoes

transmutation, changing from one element into another–the nucleus changes # of protons!

Why?•Radioactivity of an atom

depends on the ratio of neutrons (N) to protons (P)

•How is a nucleus held together? STRONG NUCLEAR FORCE

Why?• Think about it! . . . protons are all

positively charged and want to repel each other

• Neutrons act as a “nuclear glue” – they increase the strong nuclear force but don’t repel because they have no charge

Band of Stability

• N/P ratio of stable nuclei • Stable small atoms (atomic # less than 20)

are near 1/1 ratio• Stable large atoms are near 1.5/1 ratio• Predict the stability of the following:

carbon-12hydrogen-3

mercury-200uranium-238

Discovery–In the 1900’s only 3 radioactive elements were identified

–Today, all elements after bismuth are radioactive

–The larger they are, the more easily they “fall apart”

Radiation Types

1. Alpha () particles2. Beta () particles3. Gamma () rays4. Positron emission 5. Electron Capture (EC)

. . . and moreNuclear reactions have BALANCED

nuclear equations!!

(alpha) Particle

•it is a helium nucleus•symbol: He or • low energy – doesn’t penetrate foil•decreases the # of protons•never emitted with beta

42

42

Po Pb + He21084

20682

42

(beta) Particle

• it is an electron (from the nucleus)• symbol: e or • higher energy - penetrates the

skin• increases # of protons• never emitted with alpha

0-1

0-1

C N + e146

147

0-1

(gamma) Ray• high energy electromagnetic wave• no mass and no charge• higher energy – blocked only by

thick lead or thick concrete• used to treat cancer• usually is emitted with alpha or beta

U He + Th + 2 23892

42

23490 0

0

Positrons or Electron Capture

• Positron emission e–decreases # of protons– (product side of equation)

• Electron Capture, EC e (reactant side of equation)–decreases # of protons

• Neutron captured or emitted n

0+1

0-1

10

Fission & Fusion• Nuclear Fission – the splitting of a

nucleus into fragments– Very large release of energy– Used in nuclear power plants

• Nuclear Fusion – the combining of atomic nuclei– Very large release of energy– Occurs in the core of the sun & other stars– Requires high temperatures (5 million K)– Atomic explosions initiate fusion, but can’t be

controlled

• . . . and many more!

Fission & Fusion• Nuclear Fusion – the combining of

atomic nuclei– Very large release of energy– Occurs in the core of the sun & other

stars– Requires high temperatures (5 million K)– Atomic explosions initiate fusion, but

can’t be controlled

• . . . and many more!