Electronic Structure of Atoms PDF

Electronic Structure of Atoms Lecture Chapter 4 Part 1 – SHCHEM1 Natural Science Cluster Prepared by: Mc. Benrick Porras OBJECTIVES At the end of the lesson, the learners will be able to: Describe the characteristics of a wave; Relate the order of the regions of the electromagnetic...

Electronic Structure of Atoms Lecture Chapter 4 Part 1 – SHCHEM1 Natural Science Cluster Prepared by: Mc. Benrick Porras OBJECTIVES At the end of the lesson, the learners will be able to: Describe the characteristics of a wave; Relate the order of the regions of the electromagnetic spectrum in terms of their wavelength and frequency; State Planck’s equation; Solve problems related to electromagnetic radiation, its energy, wavelength, and frequency; Describe the particle-wave duality of light Properties of waves 3 Properties of Wave: 1. Wavelength (λ) - is the distance from one point on a wave to WAVES – it is a vibrating physical disturbance the same point on an adjacent wave. The highest peak of the by which energy is transmitted. wave is called the crest and the lowest point is named as the trough. 2. Frequency (ν) - is the number of waves passing per unit time. It is reported in cycles per second (s-1)which is also called hertz (Hz). 3. Amplitude (Ψ) - is a length of the electronic vector at a maximum wave. Properties of waves WAVELENGHT 3 Properties of wave: 1. Wavelength (λ) - is the distance from one point on a wave to the same point on an adjacent wave. 2. Frequency (ν) - is the number of waves passing per unit time. It is reported in cycles per second (s-1)which is also called hertz (Hz). 3. Amplitude (Ψ) - is a length of the electronic vector at a maximum wave. Properties of waves FREQUENCY 3 Properties of wave: 1. Wavelength (λ) - is the distance from one point on a wave to the same point on an adjacent wave. 2. Frequency (ν) - is the number of waves passing per unit time. It is reported in cycles per second (s-1)which is also called hertz (Hz). 3. Amplitude (Ψ) - is a length of the electronic vector at a maximum wave. The WAVE NATURE OF LIGHT Wavelength and frequency are inversely related. Wavelength and frequency are related and if multiplied will give the speed of the wave given by the equation: 3 Properties of wave: 1. Wavelength (λ) - is the distance from one point on a wave to µ= 𝝀𝝂 the same point on an adjacent wave. 2. Frequency (ν) - is the number of waves passing per unit time. It Where: is reported in cycles per second (s-1)which is also called hertz (Hz). µ = speed of the wave (m/s) ν = frequency (s-1) 3. Amplitude (Ψ) - is a length of the electronic vector at a Λ = wavelength (m) maximum wave. The WAVE NATURE OF LIGHT The WAVE NATURE OF LIGHT ELECTROMAGNETIC SPECTRUM Where: Wavelength and frequency of EM wave if multiplied will give the speed of the light c = 𝝀𝝂 c = speed of light (3 x 108 m/s) ν = frequency (s-1) given by the equation: λ = wavelength (m) The WAVE NATURE OF LIGHT The WAVE NATURE OF LIGHT 1. A yellow light emitted by a sodium vapor lamp has a wavelength of 589 nm. What is the frequency of the yellow light? c = 𝝀𝝂 Where: c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m) The WAVE NATURE OF LIGHT 1. A yellow light emitted by a sodium vapor lamp has a wavelength of 589 nm. What is the frequency of the yellow light? c = 𝝀𝝂 Where: c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m) The WAVE NATURE OF LIGHT 2. A radio station broadcasts at a frequency of 590 KHz. What is the wavelength of the radio waves? c = 𝝀𝝂 Where: c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m) The WAVE NATURE OF LIGHT 2. A radio station broadcasts at a frequency of 590 KHz. What is the wavelength of the radio waves? c = 𝝀𝝂 Where: c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m) The WAVE NATURE OF LIGHT 3. A particular electromagnetic radiation was found to have a frequency of 8.11 x 1014 Hz. What is the wavelength of this radiation in nm? To what region c = 𝝀𝝂 of the electromagnetic spectrum would you assign it? Where: c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m) The WAVE NATURE OF LIGHT c = 𝝀𝝂 Calculate the wavelength of the following radio station in the Where: Philippines. c = speed of light (3 x 108 m/s) ν = frequency (s-1) λ = wavelength (m)  FAILURES OF CLASSICAL PHYSICS Photoelectric Effect and BLACK BODY RADIATION Albert Einstein and Max Planck Blackbody radiation cannot be explained by classical physics. Black body radiation graph As the temperature of an object Classical Physics: As the temperature of a increases, it emits more blackbody blackbody increased, the frequency of the energy at all wavelengths. emitted radiation would increase without any limit. Blackbody radiation cannot be explained by classical physics. "What if energy isn’t smooth E = 𝒉𝝂 and continuous like we thought, but instead comes in little packets or chunks?" Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J) “Energy (light) is emitted or absorbed in discrete units MAX PLANCK, 1900 Father of Quantum called QUANTA.” Theory Quantization - certain things can only exist in specific, fixed amounts, rather than in a smooth, continuous way. Blackbody radiation cannot be explained by classical physics. Quantization - certain things can only exist in specific, fixed amounts, rather than in a smooth, continuous way. Consider the notes that can be played on a piano. In what way is a piano an example of a quantized system? In this analogy, would a violin be continuous or quantized?  E = 𝒉𝝂 Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J)  E = 𝒉𝝂 Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J)  E = 𝒉𝝂 Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J)  E = 𝒉𝝂 Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J)  E = 𝒉𝝂 Where: h = Planck’s constant (6.626 x 10-34 J.s) ν = frequency (s-1) E = Energy of the particle/wave (Joules, J) Einstein Explained the Photoelectric Effect with a Quantum Hypothesis Classical Physics: when using very dim light, it would take some time for enough light energy to build up to eject an electron from a metallic surface. Radiation shining on a metal surface will cause the ejection of electrons. Einstein: Regardless of intensity (how This phenomena is called bright/dim) of the light, if it doesn’t have Photoelectric Effect. enough frequency then electrons cannot be ejected. Einstein Explained the Photoelectric Effect with a Quantum Hypothesis Light must also be made of quanta which is called photons (particles of light) “Wave-particle duality of light” 𝐾𝐸𝑒𝑗𝑒𝑐𝑡𝑒𝑑 𝑒 − = 𝐸𝑜 − ϕ Light shining on a metal surface will Where: cause the ejection of electrons. This phenomena is called Photoelectric KE = Kinetic energy of the ejected electron. Effect. Eo = Energy of the incident light. Φ = Work function of the material. Classical physics can’t explain the emission spectra of atoms. Emission is the process of elements releasing different photons of color as their atoms return to their lower energy levels. Classical physics can’t explain the emission spectra of atoms. Bohr: Electrons can only exist in specific quantized energy levels around the nucleus. Electrons can absorb energy and move to a higher energy level, or release energy and move to a lower one, but this energy change is always fixed. ∆E = Energy change in orbital transition RH = Rydberg’s Constant (2.18 x 10-18 J) ni = initial orbital nf = final orbital Classical physics can’t explain the emission spectra of atoms. An electron in a hydrogen atom transitions from the 𝑛=1 energy level to the 𝑛=4 energy level. Calculate the energy of the photon emitted during this transition. ∆E = Energy change in orbital transition RH = Rydberg’s Constant (2.18 x 10-18 J) ni = initial orbital nf = final orbital Classical physics can’t explain the emission spectra of atoms. An electron in a hydrogen atom transitions from the 𝑛=1 energy level to the 𝑛=1 energy level. Calculate the energy of the photon emitted during this transition. ∆E = Energy change in orbital transition RH = Rydberg’s Constant (2.18 x 10-18 J) ni = initial orbital nf = final orbital Classical physics can’t explain the emission spectra of atoms. An electron in a hydrogen atom transitions from the 𝑛=3n=3 energy level to the 𝑛=2n=2 energy level. Calculate the energy of the photon emitted during this transition. ∆E = Energy change in orbital transition RH = Rydberg’s Constant (2.18 x 10-18 J) ni = initial orbital Nf = final orbital Classical physics can’t explain the emission spectra of atoms. An electron in a hydrogen atom transitions from the 𝑛=3 energy level to the 𝑛=2 energy level. Calculate the energy of the photon emitted during this transition. ∆E = Energy change in orbital transition RH = Rydberg’s Constant (2.18 x 10-18 J) ni = initial orbital Nf = final orbital Wave-particle duality of matter Waves can behave as particle then particles can also act as waves Louis de Broglie, 1924 Development of Quantum Mechanics UNCERTAINTY PRINCIPLE “Wave-particle duality of matter limits what we can know about the location and momentum of quantum objects (can only know one or the other, not both)” It’s so complex! Werner Heisenberg Development of Quantum Mechanics In 1926 Schrodinger wrote an equation that described both the particle and wave nature of the e-. Wave function (Ψ) describes: 1. energy of e- with a given Ψ. 2. probability of finding e- in a volume of space, given by Ψ2. Atomic orbital – region within an atom that encloses where the electron is likely to be found. By solving the Schrodinger wave equation, we arrive at Erwin Schrodinger the idea of atomic orbital and quantum numbers. ATOMIC ORBITALS AND QUANTUM NUMBERS Atomic Orbitals QUANTUM NUMBERS QUANTUM NUMBERS – Principal Quantum Number, n. Symbol: n Describes the energy level or shell of an electron. Values: Positive integers (1, 2, 3,...) Higher values of n = higher energy and farther from the nucleus. Determines the size of the electron cloud. QUANTUM NUMBERS – Angular Momentum Quantum Number, l. Shape of the “volume” of space that the e- occupies. Symbol: l Describes the subshell or shape of the orbital. Values: 0 to (n-1) for each value of n. Subshells: l = 0 → s (spherical) l = 1 → p (dumbbell) l = 2 → d (cloverleaf) l = 3 → f (complex shapes) QUANTUM NUMBERS – Magnetic Quantum Number, ml. Symbol: ml Describes the orientation of an orbital in space. Values: -l to +l (including 0). Example: For l = 1 (p orbital), ml = -1, 0, +1 (3 orientations). QUANTUM NUMBERS – Magnetic Quantum Number, ml. QUANTUM NUMBERS – Magnetic Spin Quantum Number, ms. Symbol: ms Describes the spin direction of an electron. Values: +½ (spin-up) or -½ (spin- down). Electrons in the same orbital must have opposite spins (Pauli Exclusion Principle). QUANTUM NUMBERS – Summary In your own words/analogy, explain the following … ELECTRONIC CONFIGURATION OF ATOMS The energy of electrons in an atom is quantized, which means that an electron in an atom can have only certain allowed energies. Ground-state electron configuration: The electron configuration of the lowest energy state of an atom. Electronic configuration pertains to how the electrons are distributed among the various orbitals. Type of orbital 12C 1s22s22p2 Number of electrons Energy Level Valence electrons are the electrons in the outermost energy level. Electronic configuration pertains to how the electrons are distributed among the various orbitals. Rules in Writing Electronic Configuration Rule 1: The Aufbau Principle The word 'Aufbau' is German for 'building up'. The Aufbau Principle, also called the building-up principle, states that electron's occupy orbitals in order of increasing energy. The order of occupation is as follows: 1s