Chapter 2 Things to Know

Level 1 has one s orbital, level 3 has three s orbitals

False

The 2s orbital is the same size as the 3s orbital

False

The electron path is indicated by the surface of the orbital

False (electrons are within the sphere)

a 4p orbital has more lobes than a 2p orbital

False (same p different size)

The Wave Nature of Light

-According to Maxwell light is a propagating through space electromagnetic wave composed of oscillating electric and magnetic fields -the fields oscillate in perpendicular planes that are both perpendicular to the direction of propagation

Quantization of Energy

-According to Planck hot, glowing objects could emit (or absorb) only certain quantities of energy (quanta) -the hot object's radiation is emitted by the atoms contained within it -if the atom can emit only certain quantities of energy, it follows that the atom itself can only have certain quantities of energy -thus, an atom is quantized and exists only in certain fixed quantities, rather than being continuous -Planck believed that this quantization applied only to the absorption and emission of energy by matter, not to electromagnetic waves themselves

Energy Levels

-Atoms can move from one energy state to another only by sadden jump involving a finite amount of energy (quantization of the energy) -lambda=hc/e2-e1 -Since only certain energy changes occur, the H atom must contain discrete energy levels -Thus the energy levels of all atoms are quantized

Bohr's Hydrogen Atom

-Bohr refined Rutherford's atomic model by adding the idea of fixed orbits, or energy levels for the electron traveling around the nucleus -this model allowed for the idea that electrons can become, "excited" and move to higher energy levels for brief periods of time -quantized energy levels -electron moves in a circular orbit -electron jumps between levels by absorbing or emitting a photon of a particular wavelength? -It correctly explained the emission spectrum of hydrogen but BOHR'S MODEL OF THE ATOM WAS INCORRECT : ELECTRON DOES NOT MOVE IN A CIRCULAR ORBIT

Characteristics of EM Waves

-EM waves are characterized by three variables and one constant Wavelength (lambda)- horizontal distance in space between two adjacent crests or two adjacent troughs (or any two analogous points) Amplitude-vertical height of a crest or depth of a trough (indicates the strength of its electric and magnetic fields) Frequency (V)-the number of cycles (or wave crests) per second that pass through a given point in space Speed aka Velocity (constant)- the product of wavelength and frequency, a constant that defines how fast the EM wave propagates through space -Wavelength and frequency are interdependent properties

Dual Nature of Light

-Einstein's theory of relativity signifies that energy has mass (E=mc^2)

Quantum Mechanical Model of the H Atom

-Erwin Schrodinger corrected Bohr's model of the atom by incorporating the wavelike properties of the electron (wave mechanics or quantum mechanics) and, thereby, determining the correct energy value for each energy level in the H atom -We can describe the electron mathematically, using standing waves--the stationary waves that do not travel along any length

Heisenberg Uncertainty Principle

-Heisenberg established that we cannot know exactly where a moving particle is and exactly how fast it is moving at the same time -Hence, we cannot prescribe exact paths for electrons, such as the circular orbits of Bohr's Model: the act of measuring the particle location actually interferes with the particle

Photoelectric Effect and Photon Theory of Light

-The frequency of light MUST match the threshold value for emission of the electron

Electron Spin

-Uhlenebeck and Goudsmit postualted the existence of a new intrinsic property of particles that behaved like an angular momentum -later termed spin by Pauli -One electron does not have more or less spin than another--all electrons have the same amount of spin -the orientation of the electron's spin is quantized with only two possible values , -1/2 and +1/2 -these quantized values are described to be the electron spin quantum number ms

Line spectrum

-a series of light emissions at different wavelengths -the emission spectra of different elements contain different lines, each spectrum being a characteristic of the element producing it

Line Spectrum of Hydrogen Arises Because...

-each electronic energy level in an atom is quantized -since the levels are quantized, changes BETWEEN levels must also be quantized -a specific change thus represents one specific energy, one specific frequency, and therefore one specific wavelength

F Orbitals

-first f subshell occur in level n=4 -these orbitals are not involved in bonding any compounds

Probability Distribution

-indicates the probability of finding an electron near a particular point in space around the atom's nucleus -the intensity of color is used to indicate the probability value near a given point in space -the more time the electron visits a particular point, the darker the negative becomes -This diagram is know as an electron density map; electron density and electron probability means the same thing -electron density is highest closest to the positive nucleus

Principal Quantum Number (n)

-it is independent of the other two quantum numbers -can only be a positive integer (whole #) ex.) n=1,2,3,4... -the relative SIZE of an orbital and its ELECTRON ENERGY depend on the value of n -as n increases, the electron is at a higher energy level and spends more time farther from the nucleus -orbitals with the same value of n are said to be in the same principal shell (energy level)

Diffraction of Light

-it is the result of light getting scattered from a regular array of points or lines -this scattered radiation produces a diffraction pattern on bright and dark areas allowing us to see structure -Scattered light can interfere constructively and produce a bright area, or destructively produce a dark spot

Wavelength x Frequency = Speed of Light

-light of higher frequency will have shorter wavelength -light of lower frequency will have longer wavelength

Electromagnetic Radiation

-one of the ways that energy travels through space -gamma rays have the highest energy and are short -radio waves are long and have the lowest energy

Pauli Exclusion Principle

-states that in a given atom no two electrons can have the same set of four quantum numbers -an orbital can only hold only two electrons, and they must have opposite spins because only two values of ms are allowed

How Atoms Emit Light

-they first must receive energy and become excited -the energy is released in the form of a photon -the energy of the photon corresponds exactly to the energy change experienced by emitting atom

An s orbital is always spherical

True

The hydrogen atom has 5d orbitals

True

The number of types of orbitals in a given energy level is the same as the value of n

True

Orbital Energy Levels for the Hydrogen Atom

-all orbitals with the same value of n have the same energy and are said to be degenerate

Quantum numbers and Atomic orbitals

-an atom contains 3 parameters n, l, and m1, called quantum numbers that must have specific integral values -a wave fxn with a given set of these three quantum numbers is called an atomic orbital -when values are assigned to the 3 quantum numbers, a specific atomic orbital has been defined in terms of its energy, shape, and spatial orientation

S Orbitals

-an s orbital has a spherical shape with the nucleus at its centre; a 2s orbital is larger than a 1s, a 3s is larger than a 2s, and so forth

Magnetic Quantum Number (m1)

-determines the ORIENTATION in space of the orbitals of any given type in a subshell -can be an integer from -1 to +1, including 0 -the number of possible values for m1=(2l+1)

Angular Momentum Quantum Number (l)

-determines the SHAPE of the orbital -possible values: l=0,1,2...(n-1) -orbitals having the same values of n and of l are said to be in the sam sub shell -values of l: l=0 letter used=s l=1 letter used=p l=2 letter used=d l=3 letter used=f l=4 letter used=g

D Orbitals

-do not correspond to principal quantum levels n=1 and n=2. -first d subshell occurs in level n=3 -dxz, dyz, dxy, and dx^2-y^2 have four labels that are centered in the plane that appears in the orbital label -dz^2 possesses a unique shape with two lobes that run along the z axis and a belt centered in the xy plane

Radial Probability distribution

-graph plots the total probability of finding an electron in each spherical shell versus the distance from the nucleus -atomic orbitals do not have sharp boundaries -probability of finding an electron at a particular position is greatest near the nucleus -volume of the spherical shell increases with distance from the nucleus -the size of the 1s orbital can be stated as the radius of the sphere that encloses 90% of the total electron probability

Photoelectric effect

-the emission of electrons from the surface of metals when light strikes it

Quantized Energy of Light

-the higher the frequency the greater the energy and vice versa -a bright source of light emits a dense stream of photons -a dim source of light emits relatively few photons -a photon of red light (long lambda) carries less energy than does a photon of blue light (short lambda)

Atomic spectra

-the individual colors emitted from thermally or electrically excited atoms of elements ex.) fireworks

Blackbody radiation

-the light of changing intensity and wavelength emitted from hot, dense objects -when dense solid objects absorb energy such as thermal or electrical energy, they reemit that energy in the form of light changing intensity and wavelength

P Orbitals

-the p orbitals have dumbbell shapes with different spatial orientations -one p orbital consists of two lobes, one on either side of the nucleus, and the electron spends equal time in both -p orbitals, where n>2, look like the 2p orbitals but have larger lobes

Size and Energy of Atomic Orbitals

-the size of the orbital increases -the electron is at a higher energy level -the electron is farther from the nucleus on average -the electron spends more time farther from the nucleus

Schrödinger's Wave Functions

-wave function represents an energy state of the atom -a specific wave function is termed as an ORBITAL -we do not know the movement nor the pathway of an electron

Ground State

atom in a lowest possible state

Excited State

atom with excess energy ex.) when an H atom absorbs energy from an outside source it enters an excited state

Formula's to Know

wavelength x frequency = velocity (lambda)(v)=constant (c) -The units of Frequency are cycles per second: 1s^-1 = 1 Hz -c=(lambda)(v), so v=c/lambda (frequency proportional to speed) -c=(lambda)(v), so lambda=c/v (frequency inversely proportional to wavelength -c= 3.00 x 10^8 -E=nhv (n=quantum #, h=proportionally constant, v=radiation frequency) -E=hv, where h, called Planck's constant, has the value h=6.626 x 10^-34 (proportional) -energy of a photon expressed in terms of wavelengths: E=hc/lambda (inversely proportional) -the mass of a photon of light with wavelength m= h/(lambda)(c) -The electron in an atom could have only certain allowed values of energy thus: En = -B/n^2 (B is a constant which = 2.178 x 10 ^-18) -to find the energy difference: E=B[1/ni2-1/nf2] than wavelength: lambda=hc/E -a particle with mass m moving at a speed (v) will have a wave nature consistent with a wavelength given by: lambda=h/mv