Chemistry 12: Structure and Property of Matter Flashcards Preview

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Flashcards in Chemistry 12: Structure and Property of Matter Deck (16):
1

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

2

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

3

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)

4

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
Ex:
n = 1 (1s)
n = 2 (2s, 2p)
n = 3 (3s, 3p, 3d)

5

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

Note:
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)

6

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)

7

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

8

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

9

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

10

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)

11

Stable elements

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

Excited state - one or more inner orbitals unfilled

12

Transition metals

Have partially filled d orbitals

13

Halogens

Have valence shell with s2p5

14

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

15

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.

16

Colours of wavelengths of lines

visible spectrum

about 400 nm violet
about 650 nm red