Anatomy of an Atom

Parts of an AtomNucleus• (positive, mass of 1

amu)• Neutron ( , mass of 1 amu)

Electron Cloud• Electrons ( , negligible

mass)

The Periodic Table

Atomic = # of (determine the type of atom); also # of

for neutral atomsAtomic mass = # of protons + # of

Different Versions of an Atom

are atoms that have a positive or negative charge; p ≠ e are atoms of the same element that differ in their number of (same atomic #, different atomic mass)

What is Radioactivity?

Spontaneous decay ( ) of the nucleus of an atom, usually releases (emits) a particle &/or energyCan’t when an atom will decayCan’t change the of decay (heat, electric, etc.)

Nuclear Radiation

Some nuclei are .Unstable nuclei decay and release a particle (alpha or beta) or energy (gamma)Nuclei can change into different when they decay.Types of : alpha particles, beta-particles, gamma rays

What makes things radioactive?

What happens during radioactive decay?

Alpha Particles (a)Alpha particles are made of 2 and 2 .Helium results(+) chargedMassiveBarely pass through a

.Remove electrons from matter as it passes through. (

)

What type of particles are emitted during radioactive decay?

Beta particles are formed from break down of a neutron into 1 e- and 1 proton. (-) chargedFast-moving The e- is thrown from nucleus.Faster than particlesStopped by a of metalIonize other atomsA element forms

Beta Particles (ß)

Gamma rays (γ)Electromagnetic energy stronger with frequency and lower

than light or X-rays No but they do ionizecause damage because of high energy that

.Concrete or 1.5 cm of lead can stop it from traveling through

What do they all have in common?

Ionizing- creates particles (ions)Detectable (with counter)Harmful to tissueFrom the of atoms

Half LifeTime it takes for of the substance to .Different half-lives for different Can be used to predict how old something is.

The half life of sodium-25 is 1 minute. How much of a 100 g sample of Na-25 would be left after 1 minute? How much would be left after 2 minutes?

Nuclear ForcesStability of an atom depends on the force that the nucleus together (

force).Acts between protons and neutrons. Neutrons act as “nuclear

” to prevent protons from flying apartOnly happens over a short distance.Can’t hold beyond p+

Nuclei with too many or too few

are unstable and become radioactive.More than

protons-always unstable, decay

More Nuclear Decay

Fission vs FusionFission is the down of a nucleusFission can start chain reactionsFusion is nucleiBoth release energy (E = mc2)

E= energym= massc = speed of light (3 X 108)

Helpful radiation

Can be natural-soil, sun, water, plantsOur sun emits solar radiationCan actually change DNA and cause birth defects

Smoke alarms

Treat cancer

Tracers in medicine

Tracers in geology

Nuclear power-fission

Radiation in our world