Chapter 7: Quantum Theory of The Atom Flashcards
What is a wave?
A continuously repeating change or oscillation in matter or in a physical field. Light is an example of a wave.
Light consists of oscillations in electric and magnetic fields that can travel through space. Visible light, x-rays, and radio waves are all forms of electromagnetic radiation.
Wavelength is denoted by the use of lambda and is the distance between any two adjacent and identical points in a wave (measured at its peak).
What is the frequency of a wave?
The number of wavelengths of that wave that psas a fixed point in one unit of time. (Anchored boat in water and stone dropped - the amount of waves that pass you in a second is the frequency (Frequency is denoted by the letter “v”)
How are wavelength and frequency related?
They are inversely related: The greater the wavelength, the lower the frequency and vice versa. The produced v lambda is the total length of the wave that has passed the point in 1second.
What is diffraction?
A property of waves in which the waves spread out when they encounter an obstruction or small hole the size of a wave length. Example: Street light through mesh curtain.
Planck’s Quantization of Energy
Planck studied the light emanating of off glowing solids (white a very hot amounts and red at lower amounts). He created a quantum number to measure the vibrational atoms and limit them to certain values (which he later tried to eliminate from his theory).
What is Einsteins photoelectric effect?
The ejection of electrons from the surface of a metal or from another matrial when light shines on it (however its only when the light exceeds a certain threshold value)
Bohr’s Posulates to account for the stability of the hydrogen atom and the line spectrum of the atom?
- Energy level Posulate: An electron can have only specific energy values in an atom (energy levels). Therefore, the atom itself can hve only specific total energy values.
- Transitions between energy levels: An elctron in an atom can change energy only by going from on energy level to another enegry level.
According to Bohr’s theory, the emission of light from an atom occurs when an electron undergoes a transition from an upper energy leel to a lower one and has to get rid of a photon.
How do hydrogen atoms get enough electrons to start losing them for light emission?
Through the collision of two hydrogen atoms. The result is the emission of light.
What is de Broglie relation?
Light not only has wave properites which are characterized by frequency, but also particle properties. for example, a photon has a definite energy.
Louis de Broglie theorized that matter under certain circumstances has wave properties.
What is quantum mechanics?
The branch of physics that mathematically describes the wave properties of submicroscopic particles.
Quantum mechanics challenged the notion that we do not know the exact postion of a particle or electron.
What is Heisenbergs uncertainty principle?
The more well you know where a particle is, the less well you know where a particle is going.
How many quantum numbers are needed to specify the wave function that given the probability of finding an atom?
3 (3-dimensions) - the numbers are n, l, and m
Principal quantum number “n”
The one on which the energy of an electron in an atom principally depends. It can have any positive value (1,2,3, and so on). The smaller the n, the lower the energy. Orbitals also dependent, the larger the n the larger the orbital.
Angular Momentum Quantum number “l”
Distringuishes orbitals of given n having different shapes. It can have any integer value from 0 to n-1. If the principal quantum number is 3 - then the angular must fall within that shel. (0,1,2)
Magnetic Quantum Number “ml”
Distinguishes oribtals of given n and l - that is, of given energy and shape but having a different orientation in space; allowed values are -1 to +1
Spin Quantum Number “ms”
Refers to the two possible orientations of the spin axis of the electron. (+1/2 and -1/2)
Atomic orbital shells
An s orbital has a spherical shape, though specific detials of the probability distribution depend on the value of n.
1s orbital the electron is most likely to be found near the nucleus.
2s orbital is likely to be found near the nucleus and the other in a spherical shell about the nucleus
