Chapter 07: The Quantum-Mechanical Model of the Atom Flashcards Preview

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Flashcards in Chapter 07: The Quantum-Mechanical Model of the Atom Deck (45):
1

Light

A form of electromagnetic radiation

Composed of perpendicular oscillating waves
(one = electric field, other = magnetic field)

2

Electric field

A region where an electrically charged particle experiences a force

3

Magnetic field

A region where a magnetized perticle experiences a force

4

Speed of light

c

c = 3.00 × 108 m/s

5

Wavelength

λ (lambda)

The distance between identical points on successive waves

*Inversely proportional to frequency

6

Amplitude

The verticle distance from the midline of a wave to the peak (or trough)

A measure of light intensity

*Directly proportional to total energy of wave
(larger amplitude = more force)

7

Frequency

v (nu)

v = c / λ

The number of waves that pass through a particular point in a given period of time

hertz (Hz) or cycles per second (1 s-1)

1 Hz = 1 s-1

*Directly proportional to total energy of a wave
(More frequency = more total force)

*Inversely proportional to wavelenth

8

Electromagnetic spectrum

Low energy to high:

radio
microwave
infared
visible light
ultraviolet
X-ray
gamma ray

9

Interference

The interaction between waves

10

Constructive interference

Occurs when waves that are in phase interact so that they add to make a larger wave

*Amplitudes are summed making the larger wave

11

Destructive interference

Occurs when waves that are out of phase interact so that they cancel each other out (flat line)

12

Diffraction

Occurs when a traveling wave encounters an obstacle or opening in a barrier that is about the same size as its wavelengh and it bends (diffracts) around it

*Waves diffract

**Particles DO NOT diffract (they just pass through opening)

13

Interference pattern

Inherent characteristic of all waves

Light is diffracted through two slits creating an alternating pattern

14

Photoelectric effect

The observation that many metals emit electrons when light shines on their surface

15

Quanta or photons

Light energy delivered to atoms in "packets"

16

Photon energy

E

E = hv 

v = c/λ

Thus:

E = hc/λ

17

Planck's constant

h

h = 6.626 × 10-34 J×s

18

Threshold frequency

Reached when the energy of a photon is equal to the binding energy of emitted electron

hv = Φ

or E = Φ

19

Binding energy of emitted electron

Φ (phi)

20

Kinetic energy of an ejected electron

KE = hv - Φ

Excess energy of a photon that is transferred to an electron in the form of kinetic energy

21

Wave-particle duality of light

Sometimes light appears to behave like a wave, other times like a particle

Behavior observed depends on experiment

22

Number of photons

Number of photons = Epulse / Ephoton

*Ephoton = hc/λ

23

Atomic spectroscopy

The study of the electromagnetic radiation absorbed and emitted by atoms

24

Emission spectrum

The "fingerprint" of an element in the form of a series of bright lines

Can be used to identify an element

25

Bohr model of the atom (4)

1. Energy of atom is quantized (can only have very specific amounts of energy

2. Amount of energy in atom relates to electron's position in atom

3. Electrons travel in orbits/fixed distance from nucleus
*Energy of electron proportional to distance

4. Electrons emit radiation when they "jump" from an orbit with higher energy down to lower energy orbit
*Distance determins energy of photon of light produced

26

de Broglie relation

Wavelength inversely proportional to momentum (mv)

λ = h/mv

(Wavelength = h/mass * frequency)

27

Complimentary properties

The more you know about one property, the less you know about the other

When wave nature (interference pattern) is observed, particle nature (position/which slit electron passes through) cannot be, and vice versa

28

Heisenberg uncertainty principle

Product of uncertainties in both position and speed of a particle is inversely proportional to its mass

Δx × mΔv ≥ h/4π

Δx = position uncertainty

Δv = velocity uncertainty

m = mass

29

Indeterminacy

Indefinite future = can only predict probability

30

Orbital

A probability distribution map of a region where the electron is likely to be found

31

Quantum numbers (4)

1. Principal quantum number, n

2. Angular momentum quantum number, l

3. Magnetic quantum number, ml

4. Spin quantum number, ms

32

Principal quantum number

n

Indicates the orbital (Bohr's energy level)

*As n gets larger, amount of energy between orbitals gets smaller

33

Equation for energy of a hydrogen electron

En = -RH (1/n2)

RH is Rydberg constant for hydrogen
RH = 2.18 × 10-18 J

34

Angular momentum quantum number

l

Angular momentum = what kind of/angle of orbit

l = 0, 1,... n-1

l = 0 → s
l = 1 → p
l = 2 → d
l = 3 → f

e.g.
n = 2
l = [0, 1]

35

Magnetic quantum number

ml

ml = [-l, l]

e.g.
n = 2
l = [0, 2] → d orbital
ml = [-2, 2] → 5 d orbitals

36

Spin quantum number

ms

Specifies the orientation of the spin of the electron

Value is either:
+1/2 (spins up)
or
-1/2 (spins down)

37

Describing an orbital (3)

1. n, l, ml describes one orbital
2. Orbitals with same n value = same principal energy level (shell)
3. Orbitals with the same values of n & l = same sublevel (subshell)

38

Equation for energy transition in hydrogen

ΔE = Efinal - Einitial

ΔEH atom = -2.18 × 10-18 J (1/n2final - 1/n2initial)

Energy emitted by electron is carried away by the releated photon, thus:

Ephoton = -ΔE

39

Probability density

The probability of finding an electron at a particular point in space

Probability decreases as distance from nucleus increases

40

Radial distribution function

Total probability of finding an electron at a certain distance r from the nucleus

Volume of shell also increases with distance from nucleus

41

Nodes

Where the probability drops to zero, for both probabilities

42

s orbital

l = 0

spherical shape

1 s orbital

43

p orbital

l = 1

shaped like two balloons

-1, 0, 1

3 p orbitals

44

d orbital

l = 2

shaped like four balloons

-2, -1, 0, 1, 2

5 d orbitals

45

f orbital

l = 3

shaped like eight balloons

-3, -2, -1, 0, 1, 2, 3

7 f orbitals