Chapter 4: Arrangement of Electrons in Atoms

Essential Question: What is quantum theory and how does it explain the behavior of electrons? Standard 1g To relate the position of an element on the Periodic Table of Elements to its quantum electron configuration.

Radiant Energy Modern atomic theory came from studies on light and matter. Light travels through space. Light is a form of radiant energy. Electromagnetic radiation (EMR).

Radiant Energy Late 1800’s: theory that light was a beam of wave energy. Early 1900’s: light was observed as a stream of tiny, fast-moving particles.

Waves Light travels in waves. All waves described by four traits: Amplitude Wavelength Frequency Speed

Amplitude (A) Wave height measured from the origin to the peak. Brightness or intensity depends on amplitude.

Wavelength (λ) Distance between two peaks. Units of nanometers (nm), centimeters (cm), or meters (m).

Frequency (ν) Number of waves that pass a given point in one second. Units of Hertz (Hz).

Speed Speed of light (c) travels at: 3 x 108 m/s = 186,000 miles/sec!!! At this speed, it takes light from our Sun 7 minutes to reach the earth!!!

Electromagnetic Spectrum Gamma rays, x-rays, UV rays, visible light, IR, microwaves, radio waves. Visible Light Spectrum – ROY G. BIV Red – longest wavelength, shortest frequency Violet – shortest wavelength, longest frequency

EMR Spectrum

Quantum Theory Late 1900’s: wave model of light accepted by most scientists. However, some challenges using the wave model of light. Conclusion: light is a particle that moves like a wave.

Quantum Mechanical Model Mathematical explanation of the properties of atoms that treats the e - as a wave. Describes the probability of finding an e -.

Probability & Orbitals Wave functions called orbitals. regions around the nucleus of an atom where an e - with a given energy is likely to be found. There are 4 types of orbitals,s, p, d, f.

Quantum Numbers Quantum numbers = describes properties of orbitals. Four quantum numbers.

Principal Quantum Number, n Describes size and energy of orbitals. As n becomes larger, larger atom. e - is further from the nucleus.

Angular Momentum Quantum Number, l Describes shape of orbitals.

Magnetic Quantum Number, ml Give the 3D orientation of each orbital around the nucleus. x, y, z axis in space.

Spin Quantum Number, ms Direction of spin of the e - in orbital. + ½ or – ½ spin.

s-Orbitals All s-orbitals are spherical. One orientation for s-orbitals. 2 e –’s max per s-orbital

s-Orbitals

p-Orbitals Three orientations for the p-orbitals: px , py , and pz . Orbitals are dumbbell shaped. 6 e – ‘s max per p-orbital.

p-Orbitals

d-Orbitals Five orientations for the d -orbitals. 10 e –’s max per d-orbital.

d-Orbitals

f-Orbitals Seven orientations for the f-orbitals. 14 e – ‘s max per f-orbital.

Electron Configurations Show the distribution of e – ‘s among the orbitals of an atom. Describes where the e –’s are found & their energies. Helps chemists determine how an atom will react.

Chapter 4 SUTW Prompt Describe how the electromagnetic spectrum & quantum theory help us understand the behavior of electrons. Complete a 8-10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink markers. Due Date: Tomorrow(start of class).