CHEM 1151 Exam 1 Flashcards

This covers up until electron affinity in the textbook; electronegativity, lewis structures, bonding, hybridization, etc. are not currently part of this set

Nuclide

a specific isotope of an element

lanthanides

elements with atomic numbers 58 to 71

actinides

elements with atomic numbers 90-103

All elements with atomic numbers above (___) are radioactive.

83, bismuth (bismuth is included)

What are radionuclides? What do they do?

Radionuclides are radioactive isotopes. They spontaneously emit high energy radiation and decaying into another element

What elements are found in nature?

Elements with atomic numbers less than 94. 93 and 94 are both very rare though.

Which elements are alkali metals? Notable traits?

Group 1 elements; they and their oxides form basic (alkaline) solutions when they react with water.

Which elements are halogens?

Group 17 elements

Which elements are alkaline earth metals?

Group 2 elements

Which elements are chalcogens?

Group 16 elements

What are formula units?

The smallest electrically neutral unit of an ionic compound. (ex: in an array of NaCl, the formula unit would be 1 NaCl)

What is the version of molecular mass used for ionic compounds?

Formula mass; you add up the atomic masses of the elements in the formula unit

Radiant energy is synonymous with …

electromagnetic radiation; or more accurately, electromagnetic radiation is radiant energy

Electromagnetic spectrum

a continuous range of radiant energy that includes gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, and radio waves (most to least energy)

Why is electromagnetic radiation called electromagnetic?

Maxwell theorized that they move through space with two perpendicular components: an oscillating electric field and an oscillating magnetic field

What is the wavelength of a wave?

The distance between crests of a wave; This is measured in length and is represented by 𝜆

What is the frequency of a wave?

The number of cycles that pass through some stationary point per unit of time. It’s measured in cycles/second or Hertz (Hz) and is represented by 𝜈.

Is a wave with a higher frequency lower or higher energy?

Higher

Is a wave with a large wavelength higher or lower energy?

Lower

How is wavelength related to frequency?

They’re inversely proportional. 𝜈𝜆=c, where speed is the speed of light FOR RADIANT ENERGY TRAVELLING THROUGH A VACUUM

What are Fraunhofer lines? How does Bunsen and Kirchoff’s bunsen burner experiments come into play.

Fraunhofer lines are dark spots that appear in the spectrum of sunlight (white light shone through a prism). For a while, this phenomenon was unexplained. Bunsen and Kirchoff were vaporizing elements in the flame of a bunsen burner and mapping the light emitted. They found some elements were emitting light at the wavelengths of the Fraunhofer lines. This showed that at high temperatures, atoms of each element emit a characteristic spectra. And, conversely, atoms of elements in the gaseous state ABSORB electromagnetic radiation when illuminated by an external source of radiation.

atomic emission spectra

characteristic patterns of bright lines produced when atoms are vaporized in high temperature flames or electrical discharges.

atomic absorption spectra

the narrow dark lines in an otherwise continuous spectrum; the wavelengths of electromagnetic radiation an element absorbs.

What’s the relationship between atomic absorption and emission spectrums?

For any given element, the dark lines in its absorption spectrum are at the same wavelengths as the bright lines in its emission spectrum.

What are blackbody radiators?

They’re semi-fictional objects (cast iron, etc. is a pretty good approximation), that when cold, have jet-black surfaces that absorb all the light that strikes them. The spectra they emit when heated depends only on their temperature; hotter they are the more radiation they emit at shorter and shorter wavelengths. (Essentially, they’re perfect absorbers of light when cold, and perfect radiators once hot). They don’t emit ultraviolet light.

What is significant about blackbody radiators? What discovery do they prompt?

For graphs of blackbody radiators, it’s found that they do not emit ultraviolet light. (graph falls to zero). This can’t be explained by classical physics; classical physics predicts that a very hot blackbody would emit shorter and shorter wavelengths (ultraviolet) in such immense quantities that the universe would be destroyed. It showed that there was something major missing that we still needed to understand about the universe.

What is the ultraviolet catastrophe?

It’s the death of classical physics. Classical physics can’t handle blackbody radiators; it predicts that the universe would be destroyed when you turn on an oven (when anything goes above zero Kelvin).

Max Planck was asked by the German government to improve Edison’s lightbulb. What theory did his work prompt and what major question did this answer?

His work led him to Planck’s theory of the quantization of energy, which solved the Ultraviolet Catastrophe (issue that modern physics couldn’t explain blackbody radiators’ emission patterns). He found that if you assume blackbody radiators don’t emit light as waves, but rather as particles, you can make an equation that accurately models the light emitted by a blackbody radiator. It’s why the graph tanks once it gets to UV light; it would take a ton of energy to have the necessary wavelengths produced.

What is Planck’s theory of the quantization of energy?

It’s the theory that energy is quantized and can only be emitted or absorbed in discrete packages, called quanta. It’s like a staircase; you can go up a step, or ten steps, but not half a step

What is a photon?

A quantum of light

What is a quantum?

The smallest discrete quantity of a particular form of energy

What is quantum theory?

A model of matter and energy based on the principle that energy is absorbed or emitted in discrete packages.

What does it mean if a value is quantized?

It means that it has values restricted to whole-number multiples of a specific base value.

What is a photoelectron?

An electron ejected by a photon

Photons are the building blocks of _______ the same way atoms are the building blocks of _____.

electromagnetic radiation … matter

What is the photoelectric effect?

The release of electrons from a material as a result of electromagnetic radiation striking it. (a.k.a incident electromagnetic radiation)

Albert Einstein studied the photoelectric effect. (dome, one positively, one negatively charged electrode; light was shone on the negative electrode, he’d wait and see if the circuit was completed). What conclusions did he draw from this experiment? Why did this have such a big impact on physics?

Einstein found that photoelectrons are emitted only when the frequency of the incident radiations striking something exceeds some minimum threshold frequency (𝜈₀). No matter how intense the radiation is, a photoelectron will only be produced if the light has a high enough frequency. If one photon of a certain frequency can’t do it, then neither can 1000. This conclusion provided evidence for the existence of photons and led him to his work function.

What is Φ?

Φ=h𝜈₀ ; Einstein’s work function, the minimum amount of energy required to eject an electron (from the surface of a solid metal).

What is ionization energy?

Similar to the work function, only this is the energy required to eject an electron from an isolated gaseous atom.

Einstein’s work function is KE= h𝜈 - Φ = h𝜈 - h𝜈₀. What does each part mean?

KE is the kinetic energy of the ejected electron, h𝜈 is the energy of the photon in question (h is planck’s constant, 𝜈 is the frequency of the photon), and h𝜈₀=Φ = the minimum energy required to eject an electron from this material.

Johann Balmer creates the equation λ = 3.64.56nm (n²)/(1/n² - 1/2²). What was he trying to do?

This equation was empirical; it was meant to map the wavelengths of hydrogen’s emission spectrum. If an integer 3 to 6 was input, a wavelength in the visible spectrum was produced. n=7 and n=8 produced wavelengths in the UV spectrum.

Johannes Rydberg generalized Balmer’s equation to create the Rydberg equation to include lines in the infrared and UV spectrum. He found 1/λ = R_H (1/n₁² - 1/n₂²) What were the conditions on this equation and how can it be modified?

n₁ < n₂, (this makes your answer positive, b/c dividing by a bigger number makes a smaller value) and both must be positive integers. They correspond to energy levels [inside hydrogen?]. The Rydberg equation can be used to find the wavelengths in the emission spectrum for any atom with one electron, (ex: Li+2, He+1) so long as you use the corresponding Rydberg constant. (ex: 1/RHe for helium)

What is wavenumber?

The reciprocal of wavelength (1/𝜆)

Following the Balmer and Rydberg equation, Bohr proposed a model for the atom. What was it? (equation is in a separate question) What was notable about it?

Bohr proposed a model for a hydrogen atom similar to Rutherford’s, only he rationalized why neg charged electrons didn’t spiral into the pos nucleus. He theorized the angular momentum of electrons was quantized, and so are their distances from the nucleus. He called these “allowed” distances orbitals, and said shells n=1, n=2, etc. were all fixed energy levels, and for an electron to go up or down a level, a photon equaling the energy difference between the levels is absorbed/released. HOWEVER, he thought these orbitals were 2D circles, which isn’t true. (How it differed from Rutherford: he proposed quantized energy levels)

Bohr’s model of the atom doesn’t hold true, for the most part, but there is one situation where it’s a fairly accurate representation. Which situation is this?

His model of an electron revolving around the nucleus in stable circular orbits only applies to atoms/ions with a single electron

Bohr found an equation that was associated with his model of the atom, ΔE = -2.178 × 10^-18 (1/n_final²-1/n_initial²). What does each part mean?

E is the energy difference between the two levels. If if it’s negative, that’s energy emitted because an electron has dropped down to a lower energy level. If pos, electron has moved to a higher energy level and this was the energy absorbed. n is the integer representing a certain shell/energy level. NOTE: this equation always gives us the energy change of the electron. If the question asks for the energy of the photon that was absorbed/released, know that you should always give a pos value

Louis de Broglie made a revolutionary contribution to modern physics. What did he suggest?

He suggested that like light, all matter, but especially subatomic particles, also possesses a wave particle duality.

De Broglie created the equation (𝜆 = h/(mu)). What does each part mean? How do we evaluate the results of this equation?

Looking at any object w/mass, 𝜆 is its de Broglie wavelength, h is planck’s constant, m is its mass in kg, and u is its velocity. If 𝜆 is comparable in magnitude to the size (think radius, diameter, etc) of the object, the object will exhibit wave-like behaviors.

The idea that all matter is composed of small particles dates back to literally ancient times. Greek philosophers had some thoughts on the matter. What were they?

They postulated that matter was made of an infinite number of tiny particles, and the properties of the matter were determined by the types of particles they were made of. They were close, but didn’t quite get it. They thought that sharp objects were made of “sharp” particles, soft ones “soft” particles, etc.

Conservation of mass

Matter cannot be created or destroyed. For classical physics, this is true.

Law of Constant Composition

; what made it controversial for a while?

John Dalton came up with Atomic Theory. He said that 1.) Matter consists of atoms, which are the smallest identifiable unit of matter and cannot be destroyed. 2.) All atoms of the same element are identical to each other, but are different from atoms of any other element. 3.) Atoms combine in small whole number ratios when forming compounds. Which of these statements, if any, still hold true today? What prompted Dalton to develop atomic theory?

Only statement 3 holds true. Not all atoms of the same element are identical; there are isotopes and ions. All matter does consist of atoms, but they are not the smallest identifiable unit of matter and they can be destroyed. Dalton came up with these to explain the law of constant composition, the law of multiple proportions, and conservation of mass.

Law of conservation of energy

In normal physical and chemical processes, energy cannot be created or destroyed, but it can be converted from one form to another (ex: PE to KE)

Are the laws of conservation of mass and conservation of energy always true?

They’re true in typical settings, but not all the time.

Law of conservation of mass-energy

While the total mass and energy of a system is conserved, mass and energy can interconvert. (E=mc^2, c=speed of light)

What was the significance of the cathode ray tube experiment? (J.J. Thomson wanted to figure out what a cathode ray was. Effectively, he shot a beam of electrons (without knowing what they were) through a magnetic and electrical field, adjusting the strength of each and measuring the deflection of the beam.

This experiment disproved a lot of the tenets of atomic theory. He realized the cathode ray was not light, but rather charged particles. The fact that the beam was affected by the electrical field and magnetic field (and deflected away from the negatively charged plate), revealed that the particles were negatively charged. He was also able to calculate a mass/charge ratio for the particles → found these particles had a mass that was much smaller than any known atom. He proved the existence of electrons, negatively charged subatomic particles. (atomic theory said atoms were smallest units of matter→disproved)

What did the discovery of the electron tell us about the other parts of the atom?

Revealed there must also be positively charged particles in atoms, because atoms were typically electrically neutral.

The cathode ray tube experiment led to which initial model for the atom?

J.J. Thomson proposed the plum pudding model. It’s like a spherical chocolate chip cookie; He proposed that the mass of the atom was distributed throughout its spherical volume, with negatively charged particles embedded in a positively charged substance making up most of its mass.

What was the significance of Milikan’s Oil Drop experiment? (context: Steel drum, divided into two compartments by a metal plate with a hole in the center. An atomizer (perfume bottle sprayer), was sprayed from the top. Some go through the hole into the lower compartment. X-rays are high energy rays. When they hit particles, it ionizes it and gives it a charge. The x-ray beam ionizes the air, (x-ray hits the air, when something ionizes, an electron is ejected) Some collide with the oil droplets, giving them a charge. A voltage is applied between the two plates (neg plate on bottom, pos plate on top). Some droplets are suspended after the field is adjusted. He uses the radii of the droplets to find volume, he knows their density, and uses this to find mass of the droplets, then calculate the gravitational force acting on the particles. Knowing the strength of the field, he can use this information to find the electrostatic force acting on the particle.

Millikan found that the electric charges of each particle were quantized; they were all integral (whole #) multiples of one fundamental value. This value was the charge of an electron.

What did Rutherford’s gold foil experiment reveal? (Context: Alpha particles (helium nuclei with a ton of KE) were shot at a piece of gold foil. Rutherford observed how these particles behaved.)

This experiment completely disproved the plum pudding model of an atom. If the plum pudding model was true, there would have been no deflected alpha particles. However, there was some deflection. This indicated that some alpha particles had come in contact with a very large, highly concentrated mass. (plum pudding model’s mass wouldn’t be concentrated enough to deflect an alpha particle; they had too much KE). Showed the plum pudding model to be impossible.

What atomic model did Rutherford’s gold foil experiment lead him to propose?

The nuclear atom, in which negatively charged electrons orbit the positively charged nucleus of an atom like planets (He saw it as a 3D model). The electron is mostly empty space, and the nucleus represents most of the atom’s mass.

True/false: Elements in the same group have similar chemical properties.

True

True/false: Elements in the same row have similar chemical properties.

False

What does each part of this equation mean? E = h𝜈

E= energy of one photon of light for a wave of that frequency (in Joules), h=Planck’s constant, and 𝜈=frequency of the wave

What is wave-particle duality?

It’s an important quantum mechanics principle that describes the fact that microscopic entities like electrons and photons behave like both a particle and a wave.

Is light a wave or a particle?

It’s both.

Is matter a wave or a particle?

It’s both, but only very, very small objects exhibit wavelike properties. When an object’s de Broglie wavelength and its size are of similar magnitudes, the object will have wave-like properties.

When electrostatic force is attractive, electrostatic PE is

negative

When electrostatic force is repulsive, electrostatic PE is

positive (system is less stable)

An electron is in its ground state when

it’s in the lowest energy level (n=1)

An electron is in an excited state when

it’s in any energy level above n=1 (above ground state)

How can an electron move to a higher energy orbital?

By absorbing a quantum of energy that matches the energy difference between the two orbitals

What is an electron transition?

The movement of an electron between any two energy levels

Ionization

when an electron is removed or added to an atom

matter wave

the wave associated with any moving particle

De Broglie proposed another idea for the stability of electron orbitals. What did he think?

He proposed that the orbiting electron behaves like a circular wave oscillating around the nucleus, and that an electron can only exist in an orbit if there’s an integer number of de Broglie wavelengths in the circumference of that orbital, b/c that’s the only time the wave is stable.

What is a standing wave?

A wave that oscillates back and forth within a fixed space (like a violin string)

After Schrodinger, what is an orbital defined as?

Regions where there’s a high probability of electrons being there

Erwin Schrodinger wrote the equation HΨ=EΨ. What did this calculate?

The electron energy levels of the hydrogen atom.

What are wavefunctions?

Ψ; Solutions to Schrodinger’s HΨ=EΨ equation that describe how the matter waves of an electron varies in both time and location inside the atom. Ψ doesn’t have physical meaning.

What is |Ψ^2|?

The probability density of an electron and tells us where it’s likely to be found around an atom

Quantum numbers and schrodinger’s equation? What are the quantum numbers?

Each solution to Schrodinger’s equation can be described by three quantum numbers, n, l, and m_l

What does principal quantum number n describe? What values can it have?

It describes the relative size and energy of an orbital/orbital group in an atom. It’s a positive integer. Higher values of n correspond to higher probabilities of electrons being further from the nucleus and higher energies. Orbitals with the same n value are in the same shell.

What does quantum number l describe? What values can it have?

l is the angular momentum quantum number. It describes the shape of an orbital. It’s an integer with values 0 to n-1 (always pos.). Orbitals with the same n and l values are in the same subshell.

What letter does each value of l correspond to?

l=0→s, l=1 → p, l=2 → d, l=3 → f, etc.

What does quantum number m_l describe? What values can it have?

m_l is the magnetic quantum number. It describes the orientation of an orbital. It’s an integer with a value from -l to -l (THESE ARE NOT 1’S, THEY’RE L’s)

Quantum mechanical orbits are NOT 2D concentric orbits. What’s a better description?

3D volumes of space around the nucleus with distinctive shapes, orientations, and avg distances from the nucleus.

The nth shell with have ___ (#) subshells

n subshells

The nth shell has ___ (#) orbitals

n²

Each subshell has ___ (#) orbitals

(2l +1) orbitals (NOTE THAT’S AN L)

What does quantum number m_s describe?

The spin of an electron. It has two possible values +½ (spin up) and -½ (spin down)

What is electron spin?

We don’t actually know. Electrons pair, and they can’t occupy the exact same space. These numbers describe it. There’s some quality. We don’t know what it is.

What evidence do we have of electron spin?

Two scientists shot a beam of silver atoms through a magnetic field. Some deflected one way, some deflected another.

What is the Pauli exclusion principle?

The principle that no two electrons in an atom have the same set of four quantum numbers.

What are nodes (in context of electron distribution)

Locations where |Ψ^2| is zero.

What is the Aufbau Principle?

In the ground state of an atom, the lowest energy orbitals are fully filled BEFORE filling higher energy orbitals

Any state where the electrons are not all as close to the nucleus as possible is an _ state

excited

What is penetration (electrons/orbitals)?

The ability of an electron in a given orbital to get closer to the nucleus than other electrons in different orbitals

What is shielding (electrons/orbitals)?

The idea that inner shell electrons block/reduce the effective nuclear charge experienced by valence/outer shell electrons.

Why does 2s shell get filled before 2p?

Because the inner circle of the 2s experiences no shielding (is closer to the nucleus than 1s) and also penetrates 2p. Because of that inner circle, 2s has on average lower energy than 2p, so it gets filled first.