Modern Atomic Model and EMR

OUTCOME QUESTION(S): C12-2-04 ENERGY AND ATOMIC MODELS Explain average atomic mass using isotopes and their relative abundance. Include: radioisotopes Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Include: Plank’s Equation, quantum, photon Understand the historical development of the Quantum Mechanical Model of the atom. Describe how unique line spectra are created for each element. Include: Bohr model Vocabulary & Concepts Spectroscopy Emission Line spectrum

Wavelength and frequency are inversely related Wavelength (λ - “lambda”): distance from point to the same point on the next wave. Frequency (ν – “nu” or ƒ): number of wavelengths, or cycles, that pass a point per unit time. Frequency measured in cycles per second (s-1), or the SI unit hertz (Hz) Amplitude: height of the wave from origin to crest. Wavelength and frequency do not affect amplitude Wavelength and frequency are inversely related

Composed of radiated waves of both electrical and magnetic energy Maxwell (1860) - all energy radiated from objects (including visible light) is electromagnetic radiation. Composed of radiated waves of both electrical and magnetic energy

Types of Electromagnetic radiation Memorize this wavelength range… f and λ determine what you see or feel, amplitude determines how bright or hot

It will always be - ROY G BIV Sunlight (white light) shone through a prism separates it into a continuous spectrum of colours. The different wavelength for each colour causes them to refract or bend at different angles It will always be - ROY G BIV

c = λƒ c = λν All EMR radiates at 3.00 x 108 m/s in a vacuum. This universal value (c) is a product of the wavelength and frequency of the radiated energy. “speed of light” c = λƒ c = λν

The colours seen in fireworks are a result of burning different salts The colours seen in fireworks are a result of burning different salts. Red light has a wavelength of 650 nanometres. Calculate the frequency of red light (1 nm - 1.0 x 10-9 m). c = λ ƒ ƒ = 3.00 x 108 m/s 650 x 10-9 m ƒ = 4.6 x 1014 Hz

Investigated heating objects and Planck (1900) Investigated heating objects and Burning small amounts of each element gave off a unique colour of light Used to detect a metals presence Colour Element green copper yellow sodium red strontium yellow-green barium orange-red calcium purple potassium purple-red lithium Focusing this light through a prism also produces a spectrum, but ONLY distinct lines appear

Disclaimer: This is not as simple as my “art” looks Energy emitted by a element can be separated – to produce a Line spectrum (emission spectrum) Disclaimer: This is not as simple as my “art” looks

The colored lines of the atoms - Spectral Lines - are a kind of signature (like a finger print) for the atoms. Spectroscopy and spectrophotometry are techniques used to investigated EMR emissions. C O

A photon has no mass but carries a quantum of energy Planck's Radiation Law: Energy is transmitted in discrete amounts – called quanta. EMR is a stream of tiny “packets” of quantized energy carried by particle-like photons. A photon has no mass but carries a quantum of energy

So higher frequency waves contained more energetic “packets” Energy (quantum) contained in a photon is directly related to the frequency of the radiation. Eq = hf E – energy of a quantum (Joules) h – Plank’s constant (6.626 x 10-34 J s) f – frequency of absorbed or emitted EMR So higher frequency waves contained more energetic “packets”

This is the energy per photon The blue colour of fireworks is often achieved by heating copper (I) chloride to about 1200oC. The wavelength of the blue light is 450 nm. What is the quantum of energy emitted by this light? ƒ = c λ ƒ 450 x 10-9 m = 3.00 x 108 m/s E = hf ƒ = 6.7 x 1014 Hz E = (6.626 x 10-34J· s)(6.7 x 1014 Hz) E = 4.4 x 10-19J This is the energy per photon q

Compton (1922) – experiment to show particle and wave properties of EMR simultaneously. Incoming x-rays lost energy and scattered in a way that can be explained with physics of collisions. Light is both an electromagnetic WAVE, and made of PARTICLE-like photons of energy

C12-2-04 ENERGY AND ATOMIC MODELS CAN YOU / HAVE YOU? C12-2-04 ENERGY AND ATOMIC MODELS Explain average atomic mass using isotopes and their relative abundance. Include: radioisotopes Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Include: Plank’s Equation, quantum, photon Understand the historical development of the Quantum Mechanical Model of the atom. Describe how unique line spectra are created for each element. Include: Bohr model Vocabulary & Concepts Spectroscopy Emission Line spectrum