Inside the Atom

The Nucleus

5.2

I. What’s in the nucleus?A. Atomic Number - the number of protons

in the nucleus

B. Isotopesa. Isotopes - atoms of the same element that

have different numbers of neutrons

b. Mass Number - number of neutrons plus protons in a nucleus

c. Table Pg 136

C. Nuclear Gluea. Strong nuclear force holds the protons

together only if they are nearly touching

II. Radioactive DecayA. Atomic nuclei are stable when they have

about the same number of neutrons and protons

B. In unstable atoms, the nucleus must release a particle

a. Energy is given off

b. Radioactive decay - the release of nuclear particles and energy

c. Transmutation - one element changed into another through radioactive decay

C. Some Isotopes Release Alpha Particlesa. Smoke Detectors

i. Americium-241 - undergoes transmutation by emitting an alpha particle

ii. Alpha Particle - two protons and two neutrons

iii. Creates electric current

iv. Smoke stops electric current and alarm is triggered

b. After releasing the alpha particle Americium is now Neptunium

D. Some isotopes Release Beta Particlesa. Beta particle - high energy electron from the

nucleus

b. Neutron split into proton and electron

c. Beta Particle is released with a large amount of energy

d. Because there is now an extra proton, the atomic number and element are changed

e. The mass stays the same.

III. Half - LifeA. Half-life - the amount of time required for

half a sample of the element to decayB. Half-lives are different for each elementC. Continues at a steady paceD. Carbon Dating

a. Carbon-14 is used to date dead animals, plants, and humans

b. Half-life of 5730 yearsc. Once dead the carbon stops replacing itselfd. By comparing how much is left to how much

a living organisms would have, the date can be determined

E. Nuclear Waste Productsa. Nuclear waste products are isotopes that

release large amounts of radiation

b. Contained in special waste containers

IV. New Elements by TransmutationA. Using a particle accelerator, scientists

smash alpha and beta particles into existing elements

B. The particles are absorbed and changes the existing element into a new element with a larger atomic number

C. These elements do not exist in natureD. Elements 93-112 were created this wayE. Tracer Elements

a. Radioactive isotopes are introduced into a living organism

b. The small half-lives prevent prolonged radiation

c. Able to be followed by a device that detects radiation

d. Used for medical diagnoses

Pg 142 1-4