Models of the Atom - (Physics 3)

Alpha particles

Particles that consist of two protons and two neutrons

Thomson’s model of the atom

Electrons are embedded in a larger region of positive charge

Nucleus

A region where all of the positive charge in an atom and most of its mass are found

Rutherford model

Electrons orbit the nucleus in a manner similar to the planets orbiting the sun

If electrons orbited the nucleus,

They would undergo a centripetal acceleration

Maxwell’s theory of electromagnetism

Accelerated charges should radiate electromagnetic waves, losing energy, when electrons orbit the nucleus

Glowing gases

When a potential difference is applied across an atomic gas in a tube, the gas glows

(the glow depends on the type of gas)

Emission spectrum

A diagram or graph that indicates the wavelengths of radiant energy that a substance emits

Absorption spectrum

A diagram or graph that indicates the wavelengths of radiant energy that a substance absorbs

Because no two elements give off the same line spectrum,

It is possible to use a spectroscopy to identify elements in a mixture

Spectroscopy

The branch of science concerned with the investigation and measurement of spectra produced when matter interacts with or emits electromagnetic radiation

The absorption spectrum consists of

A series of dark lines placed over the otherwise continuous spectrum

Each line in the absorption spectrum of a given element coincides with

A line in the emission spectrum of that element

Absorption lines can be used to

Identify elements in the solar atmosphere

Bohr radius

The radius of the lowest energy state in the Bohr model (corresponds to the smallest possible radius)

The energy of an emitted photon is

Equal to the energy decrease of the atom (-△E_atom)

Planck’s equation to find the frequency of the emitted radiation

E = E_initial = E_final = hf

Spontaneous emission

Once an electron is in an excited state, there’s the probability that it will jump back to a lower energy level by emitting a photon

Energy levels in an atom

When a photon is absorbed by an atom, an electron jumps to a higher energy level. When the electron falls back to a lower energy level, the atom releases a photon

Aurora australis

Charged particles from the sun sometimes become trapped in Earth’s magnetic field and collect around the northern and southern magnetic poles (light shows in the southern latitude)

Most commonly released particles

Charged particles from the sun that release into Earth’s magnetic field into a part of the atmosphere that contains oxygen (which releases green light)

Red light

The result of collisions with nitrogen atoms