Unit 5: periodicity (1)

Question 1

Spectroscopy?

Answer 1

• Uses light to study matter
• Matter absorbs and releases light, and a spectroscope can provide information about structure of matter

Question 2

Light travels as…?

Answer 2

Light can travel as particules and waves

Question 3

How does light travels as waves?

Answer 3

• Light travels through space as electromagnetic energy (EM)
• Electromagnetic spectrum includes all types of EM energy such as radio waves, gamma rays, visible light…

Question 4

Wavelenght?

Answer 4

• Lambda
• Distance between 2 peaks of troughs in a wave (m)

Question 5

Frequency?

Answer 5

• V (nu)
• Number of waves that pass a given point in space per second

Question 6

Amplitude?

Answer 6

Maximum height of a wave measured from it’s center. Affects intensity of light.

Question 7

How do wavelenghts and frequencies are proportionnal?

Answer 7

They are inversely proportional!
If wavelenght increases, frequency decreases!

Question 8

Propreties of radio waves?

Answer 8

They have long wavelenghts and low frequencies

Question 9

Propreties of gamma rays?

Answer 9

They have short wavelenghts and high frequencies

Question 10

Relationship between wavelenght and frequency?

Answer 10

Multiplied together, they give the speed of a wave, which is the c, constant speed of light (3.00 x 10*8 m/s)

Question 11

Diffraction?

Answer 11

Bending of light around an object

Question 12

Interference?

Answer 12

When light waves interact with each other and the amplitude of the resulting waves either increase of decrease

Question 13

Photoelectric effect?

Answer 13

Phenomenon in which electrons are released from the surface of a metal when light strikes it.

Question 14

What is the role of the threshold?

Answer 14

Light has to hit this threshold in order to emit electrons

Question 15

Different lights on the photoelectric effect?

Answer 15

Red light = did not eject electrons (lowest energy)

Green light = did emit electrons at energy (higher energy)

Blue light = caused electrons to be emitted with highest energy (highest energy)

Question 16

Max Planck?

Answer 16

He concluded that the energy lost or gained occured only in whole number multiples

h = 6.626 x 10*-34 (Planck’s constant)

Delta E = n x h x v

Question 17

What did Einstein propose?

Answer 17

He proposed that light consists of particules called photons

Energy of a photon is equal to a single quantum

Ephoton = hv OR = hc/lambda

Question 18

Broglie equation?

Answer 18

Lambda = h/mv

Question 19

Continuous spectrum?

Answer 19

When light passes through a prism and separates into all the wavelenghts of visible light (from red to violet)

Question 20

Line spectrum?

Answer 20

Series of discrete lines of light emitted by exciting atoms (ex: hydrogen gas)

Question 21

The Bohr model?

Answer 21

• Electrons occupy discrete energy levels
• Energy levels of an atom, or orbits, are quantized
• Specific orbits correspond to specific amount of energy

Question 22

Heinsenberg uncertainty principle?

Answer 22

• You can only predict the probable distribution of electrons
• The more certain you are about where an electron is, the less certain you are about where it is going.
• The more certain you are about where it is going, the less you are about where it is.

Question 23

Quantum mechanical model of atom?

Answer 23

• Describes how electrons are arranged in an atom
• Quantum number is a set of 4 parameters that describe atomic orbitals, where an electron is likely to be found
• n, l ml and ms

Question 24

Principal quantum number? (n)

Answer 24

• Shell
• Describes size and energy level of an orbital
• Has a positive integer: 1,2,3…
• As the n increases, energy increases and average distance of the electron from the nucleus increases.

Question 25

Angular-momentum quantum number? (l)

Answer 25

• Subshell
• Defines 3D shape of an orbital
• l = n - 1 (l can be 0)

Question 26

Exemples of l?

Answer 26

• l = 0 = s orbital (sphere)
• l = 1 = p (princpal)
• l = 2 = d (diffuse)
• l = 3 = f (fundamental)
• l = 4 = g
• l = 5 = h

Question 27

Magnetic quantum number (ml)?

Answer 27

• Defines the spatial organisation of an orbital, or how many possible shapes there are
• From - l to + l with 2(l) + 1 possibilities

Question 28

Spin quantum number (ms)?

Answer 28

• Differentiates each electron in an atom because moving electrons result in a tiny magnetic fiels
• (-1/2) and (+1/2)

Question 29

Pauli Exclusion principle?

Answer 29

No 2 electrons in an atom cannot have the same four quantum numbers!