Chapter 32 The Atom and the Quantum

In what way did Rutherford's gold-foiling scattering experiment show that the atomic nucleus is both small and very massive?

Rutherford's experiment showed that most of the alpha particles passed through the gold foil with almost no deflection. Some particles were deflected from their straight line paths as they combined. He concluded that the small number of particles that repelled were really dense.

At the time of Rutherford's gold-foil experiment, scientists knew that negatively charged electrons exist within the atom, but they did not know where the positive charge resides. What information about the positive charge was provided by Rutherford's experiment?

Scientists found out that the positive charge must be concentrated in the atomic nucleus, as seen whenever the small particles repelled backwards.

How can elements with low atomic numbers have so many spectral lines?

Spectral lines are formulated when electrons make transitions between their own energy levels. When an electron is excited it doesn't stay in its lowest state it jumps to a different state to make up for the extra energy.

How does the wave model of electrons orbiting the nucleus account for discrete energy values rather than a continuous range of energy values?

The model of electrons orbiting the nucleus accounts for discrete energy levels by considering the electron to be a wave. De Broglie proved that the discrete values of radii of Bohr's orbit are a natural effect of standing electron waves. The circumference of electron orbits follows the radii of the orbits, which also makes the energy levels discrete.

When an electron makes a transition from its first quantum level to ground level, the energy difference is carried by the emitted photon. In comparison, how much energy is needed to return an electron at ground level to the first quantum level?

The same amount of energy carried by the emitted photon to change an electron from the first quantum level to the ground level is the same amount of energy needed to return an electron at ground level to the first quantum level.

How does Rutherford's model of the atom account for the back-scattering of alpha particles directed at the gold foil?

The small number of deflected particles were repelled from powerful heavy positively charged central cores which is known as the atomic nucleus.