chem 141 exam 2 MSU Questions with 100% Correct Answers | Verified

Describe the relationship between the frequency, wavelength, and velocity (speed) of a wave. - AnswerThe more times the wave is passing through a point in space = a higher frequency, the higher frequency creates a smaller wavelength, which is why the smallest wave is a gamma wave, it has the highest frequency and the shortest distance between waves, the velocity can be measured in m/s and is composed of frequency and wavelength Calculate any one (frequency, wavelength, or velocity) given the other two. 3x10^8=(W)(V) PROBLEM: 3x10^8=W(3x10^18) - Answer-W= 1.0x10^-10 meters Rank electromagnetic radiation (gamma ray, X-ray, UV, visible, IR, radio wave, microwave) in terms of energy, wavelength, or frequency - Answer-From shortest wavelength and highest frequency Gamma, x ray, UV, visibile (pink-blue-green-yellow-red), microwave, radio wave Describe and identify experimental evidence for why electromagnetic radiation is a wave. - Answer-Constructive interference is where two waves in phase intensifies the light and deconstructive interference is where wave is opposite phase cancels out and it is dark. The double slit experiment also shows this; where the waves crisscross creates light on the screen and where they cancel out is where there is black on the screen. Visible light can be detracted and bent. Make an argument (claim, evidence, reasoning) about why we consider electromagnetic radiation as a particle. - Answer-Claim; electromagnetic radiation can be looked at as a particle. Evidence/Reasoning; During the photoelectric effect, photons were blasted at a sheet of metal. The photons being light *particles, were able to attach themselves to electrons causing them to rise in energy levels and eventually go high enough to be ejected from the metal sheet. This resulted in an emission spectrum. Explain why the existence of photons (quantized light energy) explains the photoelectric effect. - AnswerElectrons floating around in the electron cloud are attracted to the proton or protons and will need a certain amount of energy to hit them and causes the interaction to become unstable. Once the photon (light particle) hits the electron, the electron will have too much energy and the interaction will break resulting in a release of said electron.Explain how (and why) different atoms emit different wavelengths of light - Answer-Each atom has different levels of energy holding the electrons close to the nucleus, different levels of energy will be needed to eject certain electrons ex. one atom may have electrons at the energy level that violet light can eject an electron, but green light can not, the green light will then have no affect on the metal. Make an argument for why spectra are direct evidence for the existence of quantized energy levels in an atom. - Answer-The spectra shows how different light waves/particles interact with elements, since we know that different lights have different wavelengths and frequencies causing a higher level of energy or a lower level, we can tell which lights will be absorbed and emitted. Compare and contrast absorption, emission, and the photoelectric effect. Describe the role that photons and electrons play in each phenomenon. - Answer-Absorption and emission can be seen as when the photons are taken in or released back into the system, the photoelectric effect shows the electrons being ejected by the photons. Describe experimental evidence for the wave nature of electrons - Answer-The double slit experiment produced the results that electrons can create an interference pattern like a wave. Although when observed the electrons behaved like a particle again. Describe an atomic orbital and what it represents - Answer-An atomic orbital is an area of space surrounding an atom's nucleus where you can find an atom, each orbital can hold 2 electrons. Draw and/or recognize pictures of s and p orbitals - Answer-S orbitals look spherical in nature and get bigger as the coefficient increases. P orbitals look like a dumbell and also get larger with the coefficient. Describe how the model of the atom changed from Dalton through Thompson, Rutherford, and Bohr to Schrodinger. Explain why each model changed and point out the problems with the previous model - Answer-The first model of the atom was developed by JJ Thomson in 1904, who thought that atoms were composed purely of negatively charged electrons. This model was known as the 'plum pudding' model. This theory was then disproved by Ernest Rutherford and the gold foil experiment in 1911, where Rutherford shot alpha particles at gold foil, and noticed that some went through and some bounced back, implying the existence of a positive nucleus.In 1913, Niels Bohr proposed a model of the atom where the electrons were contained within quantized shells that orbited the nucleus. This was because it was impossible for the cloud of negative electrons proposed by Rutherford to exist, as the negative electrons would be drawn to the positive nucleus, and the atom would collapse in on itself. In 1926, the Austrian physicist Erwin Schrödinger created a quantum mechanical model of the atom by combining the equations for the behavior of waves with the de Broglie equation to generate a mathematical model for the distribution of electrons in an atom. Choose an atomic model to explain a phenomenon and explain why you chose that model - Answer-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. Identify valence and core electron - Answer-core electrons are those closest to the atom typically represented as the last element of the previous row such as [He] and [Ne] Valence electrons are those that do the interacting with other elements in chemical reactions, they are on outer orbitals Predict trends in atomic radii and ionization energies based on placement in the periodic table - AnswerThe radius decreases as one moves from left to right within a period because the number of protons increases and the number of energy levels stays the same. This attracts electrons more strongly and pulls them in. Ionization energy increases as one goes from left to right within a period because increased nuclear charge without added energy levels attracts electrons more, making them harder to remove. Explain the concept of effective nuclear charge and how it affects atomic radii and ionization energies - Answer-As you go across the rows of elements the atom because smaller and harder to remove electrons because more and more protons are pulling on the electrons, there are the same number of core electrons in each row so therefore more protons create a smaller atom. Apply Coulomb's law to explain periodic trends in atomic radii and ionization energies - Answer-The higher the charge the stronger it will be, the distance will also be shorterDescribe the chain of events that led from the big bang to the atoms that make up your body (For example, how were atoms like hydrogen, carbon, oxygen, and iron formed?). - Answer-The result of the big bang created a very very small space with a vast amount of heat and energy inside where there was nothing but very small particles we don't understand today. The universe then expanded and expanded. Gravitation forces began to act and particles came together eventually. Stars were giant nuclear reactors that took the hydrogen and was using the atoms for nuclear fusion. After a long time the fusion elevated and started combining hydrogen and created helium. This continued for all the naturally occurring elements. Protons were fused together to get elements such as carbon with 6 protons and nitrogen with 7 protons. Describe and explain the evidence that supports the Big Bang Theory - Answer-Scientists are observing stars and how they act. Our star is just the same in the way that nuclear fusion is taking place and making the elements for the current level that it is at. Differentiate between nuclear fusion, fission and radioactive decay. Explain how nuclear reactions are different than chemical reactions - Answer-Nuclear fusion is the combining of protons, nuclear fission is the breaking apart of protons, radioactive decay is the release of electrons, beta particles etc. to become more stable. Nuclear reactions are different from chemical reactions because nuclear reactions either add to the nucleus or take it apart, chemical reactions deal with only electrons and them sharing them