Chemistry 12: Structure and Property of Matter Flashcards Preview

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Flashcards in Chemistry 12: Structure and Property of Matter Deck (16):

The Aufbau Principle

Aufbau (means building)

An electron occupies the LOWEST energy orbital that can receive it before filling higher energy orbital →most stable condition

All orbitals related to an energy level are of equal energy Ex: the three 2p orbitals are the same energy level


Hund's Rule

For orbitals of equal energy, the lowest energy configuration for an atom has max number of UNPAIRED electrons

→other orbitals in the SAME SUBSHELL must contain ONE electron before any orbital in the subshell can contain 2 (spinning in opposite directions).

Ex: p subshell must have a single electron in each of the 3 orbitals before can have two spinning in opposite directions

-because electrons repel each other, thus this ways minimizes electron-electron repulsion a


Pauli Exclusion Principle

MAX of two electrons may occupy a single orbital, but only if the electrons have opposite spins

In a given atom, no two electrons can have the same set of four quantum numbers
• Electrons can be in the same energy level (n), same subshell (l)
• Means that an atomic orbital (subshell) can only hold 2 electrons (either spin up or down)


Subshells (number of orbitals and max number of electrons can hold)

Subshells: orbitals of different shapes and energies, as given by secondary quantum numbers; often referred to as: s, p, d, f (Smart People Don’t Forget)

o s subshell has 1 orbital (max 2 e-)
o p subshell has 3 orbitals (max 6 e-; 2 e- in each orbital)
o d subshell has 5 orbitals (max 10 e-)
o f subshell has 7 orbitals (max 14 e-)

Shell # (n) = # of subshells at each energy level
n = 1 (1s)
n = 2 (2s, 2p)
n = 3 (3s, 3p, 3d)


Electron configuration on periodic table

Group 1, 2: S (meaning outermost is S)

Group 3-12: d

Group 12-18: p

Lanthanides and Actinides: f

The ROW number on the periodic table is also the energy level (n) where the valence electrons are found.

For noble gases:
-Find the energy level in the s subshell and then use the filling pattern (will completely fill)

ex: Ar = [Ne] 3s^2 3p^6 (Ar is in row 3)

The number of columns in each block (s, p, d, f) corresponds to the max # of electrons in the subshells (ex: 2 columns for s means max 2 electrons)

Do not consider completely filled d or f subshells to be valence electrons

Halogens: valence shell with s2p5
Alkali and Alkaline Earth Metals: valence shell s
Transition Metals have partially filled d-orbitals with s (not completely filled f subshell)


Electromagnetic spectrum

Radiant energy composed of gamma rays, X-rays, ultraviolet light, infrared, visible light (small part), etc.

The energy moves through space as WAVES and has three associated variables:

1) Frequency (v): the number of waves that pass a point per second -->Hertz (Hz = 1s-1)
2) Wavelength: the distance between two identical points on a wave (like the period)
3) Amplitude: the height of the wave (related to the intensity/brightness for visible light of the wave

All electromagnetic radiation travels at about the same speed in a vacuum, 3.0 x 10^8 m/s (speed of light)

c = (frequency)(wavelength)


Quantum Theory

Quantum means fixed amount (flashes of energy)

When an element was heat it gave off a LINE spectrum instead of a continuous spectrum

-->evidence that the energy of the electrons was QUANTIZED: only be certain distinct energies (lines) associated with the atom

Planck's Hypothesis; an object can only gain or lose energy by absorbing or emitting radiant energy in QUANTA (which became known as photons and explained why energy increased in small jumps)

-->Bohr developed the first modern atomic model using the concepts of quantized energies. Model postulated a ground and excited states, and in order for an electron to go from its ground state to an excited state, it must absorb a certain amount of energy (and emitting energy if moving to ground state).
--> emit light of only certain wavelength which correspond to different colors (fingerprint of element)

-->energy levels (n) (DISTINCT)

--> one quantum of energy (light) was related to its frequency by the equation E = h x frequency

More about Planck's theory:
Einstein theorized that light had BOTH wave and particle properties (PHOTON: a particle carrying one quantum of energy) -->Wave particle duality concept


Bohr to new theory (Quantum or wave mechanics)

Bohr's orbits were replaced by orbitals
-->predicts an electron's energy and location within an atom (probability cloud in which an electron is most likely to be found)

Electrons are a variable distance from nucleus with 2 electrons per orbital

2d to 3d


Quantum numbers

Quantum numbers are used to describe each electron within an atom, corresponding to the orbital size, shape, orientation and spin of the electron

Principal quantum number (n): shell

Angular momentum quantum number (l): sublevels/subshells (s, p, d, f)

Magnetic quantum number (ml): orientation and related to angular momentum quantum number
-l through zero to +l (ex: l = 2 therefore m1 = -2, -1, 0, +1, +2)

Spin auntum number (ms): direction the electron is spinning( up or down)

EACH electron has a unique set of quantum numbers


Calculations involving Planck's constant, speed of light, energy, frequency and wavelength

speed of light = (frequency)(wavelength)

c = speed of light (3.00 x 10^8)
Frequency (nu) Hertz/Hz (1/s)
Wavelength (lambda) m (convert from nm to m by multiplying by 1 x 10^-9)

Energy = (Planck's constant)(frequency)

E = J/photon (convert 1 kJ = 1000 J) -->because of Planck's constant
h = 6.63 x 10^-34 Js
Frequency (nu) Hertz/Hz (1/s)

1 MHz = 1 x 10^6 Hz

**wavelength and frequency are inversely related (increase in wavelength decreases frequency & vice versa)


Stable elements

Noble gases (outer s2p6)-->excluding completely filled d and f orbitals

Excited state - one or more inner orbitals unfilled


Transition metals

Have partially filled d orbitals



Have valence shell with s2p5


Order of shells, subshells and orbitals

Shells (energy level - closeness to nucleus) --> subshells (s, p, d, f) --> orbitals (1 in s , 3 in p, 5 in d, 7 in f)

A max of two electrons can fit in each orbital


Electron configurations

Condensed way of representing the pattern of electrons in an atom. Use of the Aufbau build-up pattern

Number of the shell/energy level, the type of orbital, and then the number of electrons in that orbital shown as a supersubscript

**remember there is a max of two electrons in each orbital (so remember the number of orbitals in each subshell)

The sum of the supersubscripts is equal to the number of electrons = protons = identity.


Colours of wavelengths of lines

visible spectrum

about 400 nm violet
about 650 nm red