Key Terms Chapter 4

Wave like properties of light

Light is perceived in the electromagnetic spectrum in a range of wavelengths

Key terms in waves

Wavelength (l) - the distance between two successive crests

Frequency (n) - the number of waves passing a certain point in 1 s (in s-1 or Hz)

Amplitude - the maximum displacement of the wave from its midpoint/centre (intensity)

Particle properties of light

Light comes in packets of energy called photons, energy of light depends on its frequency and intensity

What did the photoelectric effect show

Showed how energy of light depended on its frequency and intensity

How do you calculate the energy of a photon

Its proportional to its frequency and planck’s constant

Electron kinetic energy

Photon emissions (ground state, excited state process)

When an atom emits a photon, it returns to ground state

What happens when an atom absorbs a high energy photon

Can cause the atom to lose one of its electrons, implies an energy gain for an electron in the atom

Quantization of energy

Each energy level is restricted to specific energy values (quantised), can be described by the following equation, where n is the energy level

Quantum number 1

Principle quantum number, symbol n

What does the principal quantum number indicate

Indicates the energy level and distance from nucleus of an electron (it is the period number, which row of the periodic table you are on)

What are the values of the principal quantum number

n can be 1,2,3… to infinity, total electrons allowed in the orbital is 2n²

Quantum number 2

Secondary/angular momentum quantum number, symbol l (fancy l)

What does the secondary quantum number indicate

It describes the shape of the orbital (subshell number)

What are the values of the secondary quantum number

allowed values from l=0 to (n-1)

What orbital does each l value correspond to

l=0 is s, l=1 is p , l=2 is d, l=3 is f

Quantum number 3

Magnetic quantum number, symbol m_l

What does the magnetic quantum number indicate

Describes the orientation of the orbital

What are the values of the magnetic quantum number

Values of m_l range from -l to +l

Quantum number 4

Spin quantum number, symbol m_s

What does the spin quantum number indicate

Describes the spin of an electron, either clockwise or counterclockwise

What are the values of the spin quantum number

Allowed values are plus or minus 1/2

Summary of the quantum numbers and what they indicate

Aufbau’s principle

electrons fill atomic orbitals of the lowest available energy levels before occupying higher energy levels

Pauli exclusion principle

No two electrons can have the same four quantum numbers

Hund’s rule

for a given electron configuration, the lowest energy state (ground state) is achieved when electrons occupy degenerate orbitals (orbitals with the same energy, like or ) singly before pairing up

Or simply: Electrons remain unpaired for as long as possible

Exceptions to electron configurations (know first 2 for sure)

Cr: 1s²2s²2p⁶3s²3p⁶3d⁵4s¹

Cu: 1s²2s²2p⁶3s²3d¹⁰4s¹

Ag: 1s²2s²2p⁶3s²3d¹⁰4s²3d¹⁰4p⁶4d¹⁰5s¹

Au: [Xe] 4f¹⁴ 5d¹⁰ 6s¹

What is an atom/ion with all electrons paired called (magnetism wise)

Diamagnetic

What is an atom/ion with unpaired electrons called (magnetism wise)

Paramagnetic

Nuclear shielding/screening

Occurs when valence electrons experience repulsion from deeper core electrons, resulting overall charge is called effective nuclear charge (z*)

Covalent radius

When atoms of the same element are bonded together, the covalent radius is half the distance between the atomic nuclei

Metallic radius

In metallic elements, half the distance between the nuclei of adjacent atoms in a crystal

Periodic trends, atomic radius

A measure of the radius of an atom, increases as you go down and decreases as you go across

First ionization energy (IE1)

The minimum amount of energy needed to remove the outer most electron from a neutral atom, increases as you go across and decreases as you go down

Ionic radius

Radius of ions, cations are always smaller than neutral atoms and anions are always larger

Electronegativity

The ability on an element to attract bonding electrons to itself, increases as you go across and decreases as you go down

Electron affinitiy

The energy change (released) when an electron is added to an atom in the gas phase, increases across and decreases down