Atom Structure

What is the first step in the separation of radioisotopes that a mass spectrometer does?

Ionization; an electron is knocked off and the radioisotopes gain a positive charge.

What is the second step in how a mass spectrometer works?

Ions are accelerated over a potential difference (∆v). Final velocity of the ions can be found by

q × ∆v = ½ mv²

Solve for v²

True or false; the mass spectrometer has a magnetic field.

True.

How to calculate the magnetic force on the moving ion in the mass spectrometer?

Fb = qv × B

How to tell which way the magnetic force is directed?

Point fingers in the direction of the velocity, then curl the fingers outward to represent B coming out of the page (or in any direction of B). The way the thumb is forced is the direction of the magnetic force.

Why does the magnetic force always point to the middle of a circle and therefore have a radius ®?

FB is always 90 degrees to the velocity vector. Therefore, Fb can also be calculated by FB = qvBsin(theta) = ma

r = mv/qB

What is the relationship of mass to radius?

If mass increases, the radius of the circle the ion moves in increases.

Photon

Particle of light

Kinetic energy of an electron knocked loose by a photon is called what?

Photoelectron. 1 photon makes 1 photoelectron. Kinetic energy can be calculated by ½ mv²

Work Function

Minimum amount of energy required to free an electron from a metal.

How to calculate kinetic energy of a photoelectron from photon energy?

KE = E(photon) - Work Function

Mass of electron

9.11 × 10^-31 kg

Energy of Photon

E photon = (6.626 × 10^-34) × frequency

Frequency = (3.00 × 10^8)/wavelength

What happens when the energy of the photon is lower than the work function?

A photoelectron will not be produced, not enough energy to knock free the electron from the metal’s surface.