Exam 2

Describe the relationship between the frequency, wavelength, and velocity (speed) of a wave.

frequency: higher frequency if amplitudes are closer together, lower frequency if they're further apart
wavelength: greater wavelength if amplitudes are further apart, shorter wavelength if waves are closer together
amplitude: if the height of the wave increases, the amplitude is larger

know c=lambda (wavelength) x weird v (frequency)

gamma rays, x rays, UV, visible light (VIBGYOR), infrared, microwave, radio wave
left side: short wavelength, high frequency and energy

right side: long wavelength, low frequency and energy

Double slit experiment: waves interfere with each other to give that striped pattern due to constructive and destructive interference (which happens in waves)

Electromagnetic radiation is a wave and we can see this through the double slit experiment. Waves of light were shown upon a barrier, and as they passed through each slit, they diffracted, which caused both constructive and destructive interference. Due to this, the constructed/destructed waves made a striped pattern on the back surface of the experiment. Since waves have constructive and destructive interference, we can conclude that electromagnetic radiation (light) is a wave.

Many metals emit electrons when electromagnetic radiation shines on the surface. The light is transferring energy to the electrons at the metal's surface where it is transformed into kinetic energy that gives the electrons enough energy to leave the atoms in the metal. Only lights with higher frequencies allow for an electron to be ejected. If you increase the intensity of that light, more electrons will fly off, however, if lower frequency light that does not cause the metal to emit an electron are shone on the metal, no matter how intense, the metal will never emit an electron. If electromagnetic radiation was only a wave, increasing the intensity of any light would cause an electron to be emitted from the metal. This is how we know electromagnetic radiation is a particle.

purplelue lights will eject electrons while red light will not

E= h (constant) x v (frequency)

Explain why the existence of photons (quantized light energy) explains the photoelectric effect.

Many metals emit electrons when electromagnetic radiation shines on the surface. The light is transferring energy to the electrons at the metal's surface where it is transformed into kinetic energy that gives the electrons enough energy to leave the atoms in the metal. Only lights with higher frequencies allow for an electron to be ejected. If you increase the intensity of that light, more electrons will fly off, however, if lower frequency light that does not cause the metal to emit an electron are shone on the metal, no matter how intense, the metal will never emit an electron. If electromagnetic radiation was only a wave, increasing the intensity of any light would cause an electron to be emitted from the metal. This is how we know electromagnetic radiation is a particle.

each element has electrons of different energies; the energy changes between the energy levels are also different, so each element will have a different emission and absorption spectra

Emission spectrum: generated by the hot gas of an element going through a prism; forms black spectrum with only a few lines of light
Absorption spectrum: generated by a light shining on a hot gas of an element going through a prism; form almost a full spectrum with only a few lines of light missing (lines missing are the same found in the emission spectrum)

absorption and emission spectra are inversely related

Spectra are the direct evidence for the existence of quantized energy levels in an atom because both atomic absorption and emission spectra show light of only specific wavelengths, which means that there is a quantized energy level in which light will either be absorbed or emitted.

emission spectra: emit photons of certain wavelengths based on quantized energy levels when the electron is moving down an energy level
absorption: absorbs photons of certain wavelengths based on quantized energy levels when the electron is moving up an energy level
photoelectric effect: when light shines on a certain material, electrons will be emitted if the light is over the threshold frequency

in the photoelectric effect an atom absorbs a photon, resulting in the ejection of an electron. this process is called ionization

Double slit experiment

wavelength= h/m(kg) x velocity

Electrons are not held by orbits.

the area of highest probability where electrons will be found; orbitals can hold a certain amount of electrons depending on how close they are to the nucleus

s orbitals are circular, p orbitals look like dumbbells

orbitals

only up to 8 valence electrons

Dalton-matter is composed of atoms (model looks like O); there are electrons and protons
Thompson-plum pudding model (electrons in a soup of positive charge); electrons are in a cloud
Rutherford-positive charged core surrounded by negative charged electrons; didn't explain why atoms only emit light at certain wavelengths
Bohr-electrons circle in specific orbitals; we cannot know where the electron is and it's energy
Schoedinger-quantum mechanical model of the atom; predicted odds of finding an electron

The Schrodinger model is the best, it covers most of the bases and does not have obvious flaws like the others. The model would work in Rutherford's gold experiment. Particles would still fly through and possibly hit the proton. This model also disproves the theory that electrons are in specific rings orbiting the atom. Heisenburg's uncertainty principle also supports the "cloud" of electrons because it states that we can not not both the position and velocity at the same time.

electron configurations

atomic radii decreases across a row and increases down a period
ionization energies increase and then have a big jump when a core electron is removed

ENC is the number of protons in the nucleus subtracted by the number of protons screened by core electrons; ENC decreases atomic radii; affects ionization energy because as electrons get closer to the nucleus they become more difficult to remove because eventually you will have start pulling from the core electrons

F=q1q2^2

With the removal of an electron, quantized energy levels can be constructed from the ionization energies due to the electron removal and jumps in ionization energy (coinciding with the periods of the periodic table).

coulombs' law is like particles repel and unlike charges attract so attractive protons are attracted to negatively charged electrons.

Mg2+ is bigger cause it has more protons, despite their valence electrons being the same energy level.

At first, no protons, neutrons or atoms (too hot). After a microsecond, quarks and gluons were able to form stable structures and protons and neutrons appeared. The temperature dropped more to allow some protons and neutrons to stick and stay together. After a billion years, things began to heat up again. As clumps of mostly hydrogen became more dense, atoms collided with one another. At the same time, gravitational attraction caused matter to condense and draw in more hydrogen. Atoms began to undergo nuclear fusion, thus stars were created. As star's inner temperature heats up enough energy is available to produce other fusion reactions. Further collapse of the star's core increases temperature, and carbon's nuclei could fuse, leading to new types of nuclei.

Redshift is one piece of evidence that is backed by the Doppler Effect stating that frequencies extended over distances can decrease which causes the wavelength to increase (the increased wavelength color is red). This shows an idea of the central area of where the rapid expansion took place. The Cosmic Microwave Background Radiation which is the left-over radiation from the Big Bang, provides evidence that the fog of radiation that exponentially expanded formed the Universe.

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In fusion, electrostatic forces repel the two atoms after their initial attraction phase (when the two nuclei attract the valence electrons and when potential energy is at its lowest) up until a certain point where potential energy is at its highest peak. Then, strong nuclear force pulls the atoms together overriding the electrostatic force and making the atoms collide to form a new atom, a releasing of energy, and neutrons

Atoms do not have macroscopic properties like boiling or melting points because they are a singularity. Color does not show up on the microscopic scale rather the macroscopic. Therefore, atoms do not have color due to their small size and isolation.

to keep a molecule stable, a third body is necessary because it needs to oscillate back and forth in the potential well, otherwise the kinetic energy will keep increasing which makes the interaction unstable

molecular orbital theory: one pair of electrons in bonding orbital, bond is stable; one pair in bonding orbital and one in anti bonding orbital, bond is not stable; as temp increases, bonds are more likely to be broken (higher meltingoiling points, stronger the interaction is)

A photon is absorbed promoting movement to higher energy level, it immediately moves back down emitting a photon making metal shiny. Electrons are free flowing allowing metal to conduct electricity. Since atoms can move with respect to one another metals are ductile.