CHEMISTRY Chapter 4 Arrangement of Electrons in Atoms Southern Boone County HS William Palmer

CHEMISTRY CHAPTER 4 Properties of Light Electromagnetic Radiation Wavelike behavior Visible light X-Rays Ultraviolet Infrared

CHEMISTRY CHAPTER 4

Wavelength-Distance between corresponding parts of a wave (lambda) Frequency-Number of waves that pass a point in a given time (v). Measured in hertz (HZ)

CHEMISTRY CHAPTER 4 c is speed of light 186,000 miles/sec frequency X wavelength = speed of light c=f λ λ =c/f f=c/ λ So what? As wavelength increases, frequency decreases As wavelength decreases, frequency increases

CHEMISTRY CHAPTER 4 Photoelectric Effect-emission of electrons when a light shines on a metal.

CHEMISTRY CHAPTER 4 Photoelectric Effect-emission of electrons when a light shines on a metal. Light must be of a high frequency. Hard to explain with wave theory of light.

CHEMISTRY CHAPTER 4 Max Planck (1900) Objects emit light in small packets called quanta. The Quantum Theory

CHEMISTRY CHAPTER 4 Quantum of energy is the smallest amount of energy that can be lost or gained by an atom.

CHEMISTRY CHAPTER 4 Einstein (1905) Electromagnetic radiation has a dual wave-particle nature! WOW

CHEMISTRY CHAPTER 4 HYDROGEN ATOM LINE-EMISSION SPECTRUM (WOW THAT IS A MOUTHFUL) What does it mean?

CHEMISTRY CHAPTER 4 What does it mean? When a current is passed through a gas light is emitted. In hydrogen gas, some of the light is lost-not in spectrum. This indicates that a specific amount of energy from the light was absorbed by the atom.

CHEMISTRY CHAPTER 4 Neils Bohr (1913) Electrons in orbits Different electrons have different energy levels (like rungs on a stepladder) When in orbit an electron has constant energy When electron goes to a higher energy state it moves up the ladder (absorption) When electron goes to a lower energy state it moves down the ladder (emission)

CHEMISTRY CHAPTER 4 Questions 1-5 page 103 Try questions 1-3, page 110 PPT not ready yet…

CHEMISTRY CHAPTER 4, sec 2 HEISENBURG UNCERTAINY PRINCIPLE-It is hard to tell the location of an electron. Or….in formal words….

CHEMISTRY CHAPTER 4, sec 2 HEISENBURG UNCERTAINY PRINCIPLE- It is impossible to simultaneously tell the position and velocity of an electron or other particle. You can tell one but not the other.

CHEMISTRY CHAPTER 4, sec 2 QUANTUM NUMBERS AND QUANTUM ORBITALS Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals.

CHEMISTRY CHAPTER 4, sec 2 PRINCIPAL QUANTUM NUMBER (n) Main energy level occupied by an electron. Positive integers 1, 2, 3, 4 ….

CHEMISTRY CHAPTER 4, sec 2 AS n INCREASES, THE ELECTRON’S ENERGY AND DISTANCE FROM THE NUCLEUS INCREASE.

CHEMISTRY CHAPTER 4, sec 2 So, which has more energy- quantum number 4 or quantum number 6? Which is closer to the nucleus of the atom?

CHEMISTRY CHAPTER 4, sec 2 There are four types of Quantum Numbers: 1) Main Quantum Number 2) Angular Momentum Quantum Number 3) Magnetic Quantum Number 4)Spin Quantum Number

CHEMISTRY CHAPTER 4, sec 2 Angular Momentum Quantum Number (l)-Indicates the shape of the orbit.

CHEMISTRY CHAPTER 4, sec 2 S ORBITALS

CHEMISTRY CHAPTER 4, sec 2 P ORBITALS

CHEMISTRY CHAPTER 4, sec 2 D ORBITALS

CHEMISTRY CHAPTER 4, sec 2 F ORBITALS

CHEMISTRY CHAPTER 4, sec 2 Magnetic Quantum Number (m)-Indicates the orientation of the orbit around the nucleus.

CHEMISTRY CHAPTER 4, sec 2 Spin Quantum Number (-1/2, +1/2)-Indicates the fundamental spin state of the electrons of the orbit around the nucleus.

CHEMISTRY CHAPTER 4, sec 2 s = sphere p = dumbbell d= complex dumbbell f=very complex shape

CHEMISTRY CHAPTER 4, sec 2 PRINCIPAL QUANTUM NUMBER (n) SUBLEVELS IN MAIN ENERGY LEVEL ORBITALS PER SUBLEVEL ORBITALS PER ENERGY LEVEL ELECTRONS PER SUBLEVEL ELECTRONS PER MAIN ENERGY LEVEL 1S1122 2S1428 2P3468 3S P396 3D S P D F

CHEMISTRY CHAPTER 4, sec 2 Try questions 1-3, page 110

CHEMISTRY CHAPTER 4, sec 3 Electron Configuration The goal of this section is to figure out how electrons are arranged in an atom. There are three rules.

CHEMISTRY CHAPTER 4, sec 3 Electron Configuration Rule 1: Aufbau Principle-an electron occupies the lowest energy orbital that can receive it.

CHEMISTRY CHAPTER 4, sec 3 Electron Configuration Rule 2: Pauli Exclusion Principle- No two electrons can have the same set of quantum numbers.

CHEMISTRY CHAPTER 4, sec 3 Electron Configuration Rule 3: Hund’s Rule –Orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron.

CHEMISTRY CHAPTER 4, sec 3 Sample Problem The electron configuration of Boron is 1s 2 2s 2 2p 1. How many electrons are present in an atom of Boron? (2+2+1 = 5 electrons) What is the atomic number of Boron? (protons = electrons so with 5 electrons there are 5 protons so Atomic No. of Boron = 5)

CHEMISTRY CHAPTER 4, sec 3 Sample Problem The electron configuration of Boron is 1s 2 2s 2 2p 1. Write the orbital notation for Boron. ↑↓ ↑↓ ↑ 1s 2s 2p

CHEMISTRY CHAPTER 4, sec 3 Practice Problem The electron configuration of Nitrogen is 1s 2 2s 2 2p How many electrons are in Nitrogen? 2. What is the atomic number of Nitrogen? 3. Write the orbital notation for Nitrogen.

CHEMISTRY CHAPTER 4, sec 3 Practice Problem The electron configuration of Fluorine is 1s 2 2s 2 2p How many electrons are in Fluorine? 2. What is the atomic number of Fluorine? 3. Write the orbital notation for Fluorine.

CHEMISTRY CHAPTER 4, sec 3 Second Period Elements See chart page 116 Third Period Elements See chart page 117 Fourth Period Elements See chart on page 118 FIGURE 19, PAGE 116, IS WHERE YOU LEARN HOW THE ELECTRONS FILL THE ORBITALS

CHEMISTRY CHAPTER 4, sec 3 Second Period Elements See chart page 116 Third Period Elements See chart page 117 Fourth Period Elements See chart on page 118 FIGURE 19, PAGE 116, IS WHERE YOU LEARN HOW THE ELECTRONS FILL THE ORBITALS

CHEMISTRY CHAPTER 4, sec 3 FIGURE 19, PAGE 116, IS WHERE YOU LEARN HOW THE ELECTRONS FILL THE ORBITALS

CHEMISTRY CHAPTER 4, sec 3 Sample Problem Write the electron configuration for a Rubidium atom. (Atomic Number = 37) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 1 Write the Noble-gas configuration for Rubidium. [Kr] 5s 1

CHEMISTRY CHAPTER 4, sec 3 Sample Problem Identify the elements in the second, third, and fourth periods that have the same number of highest energy level electrons as Rubidium. Rubidium has one electron in its highest energy level…(the 5 th ). Other elements that have one electron in their highest energy level are: Li, Na, and K.

CHEMISTRY CHAPTER 4, sec 3 Practice Problem Write the electron configuration and Noble gas notation for a Barium atom. (Atomic Number = 56) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 6 6s 2

CHEMISTRY CHAPTER 4, sec 3 Practice Problem Write the electron configuration and Noble gas notation for a Barium atom. (Atomic Number = 56) 1s 2 2s 2 p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 6 6s 2 [Xe] 6s 2

CHEMISTRY CHAPTER 4, sec 3 Practice Problem Write the Noble gas notation for a Gold atom. (Atomic Number = 79) 1s 2 2s 2 p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 6 6s 2 [Xe] 4f 14 5d 10 6p 1

CHEMISTRY CHAPTER 4, sec 3 Practice Problem Identify the elements in the sixth period that have one unpaired electron in their 6s level. Au, Cs, Pt

CHEMISTRY CHAPTER 4, sec 3 Practice Problem Let’s try the work sheet on Chap 4, sec 3.