unit 3 electron configuration and modern atomic theory

UNIT 3ELECTRON CONFIGURATION AND

MODERN ATOMIC THEORY

Neon signs are formed from glass tubes. An electric current passing through the gas in each tube makes the gas glow with its own characteristic color. You will learn why each gas glows with a specific color of light.

Section 2 – Atomic Emission Spectra

prism

helium (He)lamp

prism

white light continuous spectrum

elements discrete lines

Atomic Emission Spectra

Atomic Emission Spectrum of Hydrogen

Bohr Model

In a Bohr atom, the electron is a particle that travels in specific, fixed orbits, but never in the space between orbits.

Energy absorption and light emission in a Bohr atom

When an atom absorbs energy, an electron is excited to a higher energy orbit. (excited state)

The electron then transitions back to a lower energy orbit and emits a photon of light.

Energy absorption and light emission in a Bohr atom

Electrons in their lowest energy level

Electrons are in higher energy levels

Atomic Emission Spectra

Atomic Emission Spectra

Excited atoms emit light of only certain wavelengths.

The wavelengths of emitted light depend on the element.

Each element gives a different flame color and has a different spectral fingerprint.

Atomic Emission Spectra

Bohr's Model of the Atom

Bohr's Model of the Atom

electrons only occupy specific, fixed orbits…

Summary of Bohr Model

… of fixed energy based on energy level (or shell).

Development of Atomic Models

1. Rutherford's model of the atom could NOT explain…

A. any properties of elements.

B. the chemical properties of elements.

C. the distribution of mass in an atom.

D. the distribution of positive and negative charges in an atom.

Quick Quiz!

2. Bohr's model of the atom proposed that electrons are found…A. embedded in a sphere of positive

charge.B. in fixed positions surrounding the

nucleus.C. in fixed orbits of specific energy.D. orbiting the nucleus in a single fixed

circular path.

Quick Quiz.

3. The lines in the emission spectrum for an element are caused by…

A. the movement of electrons from lower up to higher energy levels.

B. the movement of electrons from higher down to lower energy levels.

C. the electrons in energy levels in the ground state.

D. the electron locations of an atom.

Quick Quiz.

4. Which transition in an excited hydrogen atom will emit the lowest energy of light?

A. E2 to E4

B. E4 to E1

C. E3 to E2

D. E3 to E4

Quick Quiz.

longest wavelength