ca-inspire-chemistry-sampler

COLLECT EVIDENCE

Use your Science Journal to

record the evidence you collect as

you complete the readings and

activities in this lesson.

INVESTIGATE

GO ONLINE

to find these activities and more resources.

Laboratory: The Photoelectric Effect

Use mathematical and computational thinking to

observe patterns

in the stability and

instability of physical systems.

Inquiry into Chemistry: Design Atomic Models

Plan and carry out an investigation to

create a model

of the charged subsections

of an atom.

Disciplinary Core Ideas

Crosscutting Concepts

Science & Engineering Practices

3D THINKING

Bohr’s Model of the Atom

The dual wave-particle model of light accounted for several previously unexplainable

phenomena, but scientists still did not understand the relationships among atomic

structure, electrons, and atomic emission spectra. Recall that hydrogen’s atomic

emission spectrum is discontinuous; that is, it is made up of only certain frequencies of

light. Why are the atomic emission spectra of elements discontinuous rather than

continuous? Niels Bohr, a Danish physicist working in Rutherford’s laboratory in 1913,

proposed a quantum model for the hydrogen atom that seemed to answer this question.

Bohr’s model also correctly predicted the frequencies of the lines in hydrogen’s atomic

emission spectrum.

Energy states of hydrogen

Building on Planck’s and

Einstein’s concepts of quantized

energy, Bohr proposed that the

hydrogen atom has only certain

allowable energy states, as

illustrated in

Figure 10

. The lowest

allowable energy state of an atom

is called its

ground state.

When an

atom gains energy, it is said to be

in an excited state.

FOCUS QUESTION

Why does every element produce a unique atomic

emission spectrum?

LESSON 2

QUANTUM THEORY AND THE ATOM

C05_017A

Nucleus

Ground state

Excited state

Electron

Nucleus

Electron

Figure 10

The figure shows an atom that has one electron. Note that the

illustration is not to scale. In its ground state, the electron is associated with

the lowest energy level. When the atom is in an excited state, the electron is

associated with a higher energy level.

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Module 4 • Electrons in Atoms