Chemistry 1-3: Atomic Emission Spectra, & Modern Atomic Theory

Section 3: Atomic Emission Spectra and the Bohr Model

Multiple Choice

All matter has ___ and occupies space

• mass

• particle

• element

• molecule

Multiple Choice

How many electrons does one neutrally charged atom of argon have?

• 18

• 22

• 40

• 58

Multiple Choice

How many electrons are in Radium-226

• 88

• 138

• 226

• 314

Multiple Choice

How many Neutrons are in Radium-226

• 88

• 138

• 226

• 314

Lesson Objectives

• Describe the movement of electrons in atoms

• Describe the Bohr Model and how it relates to valence electrons

• Compare and contrast the different electron shells in an atom

Chemistry in your life

• A pilot light is the ignition source for a natural gas furnace, which fuels the energy for many buildings

  • Usually it burns a blue color​, but can sometimes be found burning different colors

    • What does this mean, and when should you go for repairs?

Properties of Light

• Light has properties of both particles and waves

  • Shows wavelength​ behavior as it travels through space

    • Different Wavelengths are different colors

  • When light strikes something, it behaves like a particle

• Light is a form of energy and electromagnetic radiation

Electron Movement in Atoms

• Electrons exist naturally in a ground state

  • Anything higher than the ground state is called an excited state

• When an element is in a gaseous state and gains energy, electrons become excited and unstable

  • As the electron is released, light is released

    • Specific wavelengths of light released depending on the element

• Atomic Emission Spectrum: the pattern formed when light emitted by an element is separated into the different wavelengths it contains

Atomic Emission Spectra

• Each Element emits specific wavelengths

  • The atomic emission spectrum of each element is like a fingerprint

    • No two have the same spectrum

    • The spectrum does not change for an individual element in any circumstances

• It is possible to identify the elements in a mixture based on it's atomic emission

Electrons in Orbit

• Niels Bohr

  • Danish physicist

  • Proposed that electrons move in circular orbits around the nucleus

  • Each orbit have a fixed level of energy, and are called energy levels

    • When provided the ​right amount of energy, electrons can jump from one level to another

      • Quantum: the amount of energy required to jump an electron from one energy level to another

        • can vary based on where the electrons are and distance from the nucleus

The Bohr Model

• ​Energy Levels in an atom are not equally spaced

  • Higher energy levels are closer together than lower energy levels​

• The Bohr Model explains the specific Atomic Emissions of each element

  • Each line in the spectrum corresponds to a specific electron in transition​

• ​The Bohr Model is not entirely correct, but serves as a simple model of certain properties​

Writing the Bohr Model

• We can visualize the Bohr Model through pircutre represntitives

  • The nucleus is in the middle

  • Rings for the different levels of the electron cloud

    • The innermost ring can hold two electrons

    • Every other ring can hold 8 max

Writing the Bohr Model Sample 1

• Draw the Bohr Model for Hydrogen

  • Hydrogen has one electron and one proton

  • Draw the proton in the center, and the electron on the first ring

Writing the Bohr Model Sample 2

• Draw the Bohr Model for Calcium

  • Identify the number of Protons & Electrons

  • Put Protons in the middle, Electrons on the rings

    • 2 on the first ring, up to eight on all others

Multiple Choice

What is the lowest possible energy level that an electron can occupy?

• Excited state

• Fundamental state

• Ground state

• Outermost state

Multiple Choice

Which energy levels are closer together: Higher energy levels or Lower energy Levels?

• Higher

• Lower

Multiple Choice

"The amount of energy required to jump an electron from one energy level to another" is known as what?

• Electron excitement

• Quantum

• Spectral energy

• Isotopic power

Match

Match Vocabulary term to the definition

• Isotope

• Ground State

• Quantum

• Molecule

• nucleus

An atom that has a different number of neutrons than usual

The natural, lowest energy level of an electron

The amount of energy an electron needs to jump from one energy level to another

A combination of two or more atoms

the center of the atom, where protons and neutrons are located

• An atom that has a different number of neutrons than usual

• The natural, lowest energy level of an electron

• The amount of energy an electron needs to jump from one energy level to another

• A combination of two or more atoms

• the center of the atom, where protons and neutrons are located

Multiple Choice

True or false: The atomic emission spectrum of each element is unique, like a finger print

• True

• False

Revising the Atomic Model

• 1926: Erwin Schrodinger

  • Proposed an equation that described the behavior of the electron in a hydrogen atom

    • Lead to discoveries about electrons in other atoms and the development of the Quantum Mechanical Model​

      • Similar to the Bohr model with electrons being limited to certain values

      • Different from Bohr model because electrons don't follow an exact path

Atomic Orbital

• Atomic Orbital: an area around the nucleus where there is a high probability of finding an electron

  • Electrons move around the nucleus, so you can't guarantee their exact locations

  • Boundaries are not clear and distinct but are fuzzy

The Shell Model

• The shell model of the atom is a simplified version of the quantum mechanical model

  • Described with four quantum numbers

    • Each shell has one or more sub-shells inside of it (l)

      • s, p, d, f

    • Each sub-shell holds at least one orbital that holds 2 electrons each

      • s= 1 orbital, 2 electrons

      • p=3 orbitals, 6 electrons

      • d= 5 orbitals, 10 electrons

      • f=7 orbitals, 14 electrons

S-Orbitals

• Every shell has one s-orbital, which has a spherical shape

• The probability of finding an electron does not depend on the direction the orbital is rotated

P-orbital

• Every shell on the second energy level upwards has three p-orbitals

  • Dumbbell-shaped, with 3 orbitals

    • Can face different directions

  • Electrons are found anywhere in the shape itself, but not outside of them

D-Orbitals

• Ever shell from the third level up has a d-orbital

  • 5 orbitals holding 10 total electrons

  • "The Donut Orbital"

F-Orbitals

• Every shell from the fourth level up has a f-orbital

  • 7 orbitals holding 14 total electrons

  • Have a shape too complex to show as a picture

Atomic Orbitals

• Each orbital has different energy levels

  • s < p < d < f​

Match

Match the sub shell shape to its name

S

p

d

• S

• p

• d

Match

Match the number of electrons each sub shell can hold to the sub shell name

• 2

• 6

• 10

• 14

S

p

d

f

• S

• p

• d

• f