Use pg. 236-237

As scientists learned more about __________________, they also began to learn more about new kinds of __________________. A German scientist named Wilhelm Konrad ___________________ discovered a new, invisible, but highly penetrating form of radiation called the ____________.

Roentgen observed that the mysteries radiation "____" could penetrate both cardboard and _______! A number of X-ray tube operators were over-_____________ and died before the effects of X-rays on living ____________ were understood. X-rays can penetrate soft _____________ of the body but are stopped by __________ and other concentrated tissue masses.

Use pp. 238-241

In 1895, Ernest __________________ began to study with _______________. Rutherford performed many experiments with radiation and named 3 types: ____________ particles, ___________ particles, and _____________ rays. Fig. 7.13 (pg. 239) shows that beta particles have a _______________ charge like the electron, gamma rays have _______ charge, and alpha particles have a ______________ charge like protons.

Rutherford designed an experiment to probe the atom using _____________ particles as atomic ________________. A beam of _______________ particles was "shot" at a thin sheet of ____________ foil. Most alpha particles passed straight _____________ the foil as if it were made of _______________ ______________. But a few alpha particles ____________________ from the foil. The rebounding particles must have been repelled by the atoms in the gold foil.

Rutherford concluded that the metal atoms in the foil must contain:

• a _______________ - a tiny core that is very ___________ in volume, __________ compared to the rest of the atom, and intensely _____________
• an ______________ cloud - an "envelope" that is very ______________ in volume, _____________ compared to the nucleus, and _________________ charged

Rutherford calculated that a gold atom has __________ protons in its _____________ but their total mass was less than half the mass that Rutherford calculated for the nucleus. So he reasoned that protons were not alone in the ______________ and inferred the nucleus must also contain additional, ________________ (or "neutral") particles called __________________.

Eventually, Niels Bohr figured out that the electrons revolved around the nucleus like planets orbiting the sun. The electrons move in 3-dimensional regions called electron shells.

The sum total of their work lead to a model of the atom called the Bohr-Rutherford Atom.