What is the evidence that electron energies in an atom take only certain values?

Gases emit and absorb light only at a set of sharply defined wavelengths characteristic of the element, which can only happen if the energy changes available to their electrons are themselves restricted to particular values.

What is an excited state?

An excited state is any arrangement in which an electron has been raised to a higher energy level than it would occupy in the ground state.

How can a photon excite an atom, and what condition must the photon satisfy?

The photon is absorbed and lifts an electron to a higher level, but only if its energy exactly matches the difference between two levels, because the electron cannot end up anywhere in between.

CCEA A-Level Physics 1210

Physical Quantities, Scalars and Vectors

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Moments and Equilibrium

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Linear Motion and Dynamics

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Newton's Laws of Motion

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Linear Momentum and Impulse

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Work, Energy and Power

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Resistance and Resistivity

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Waves

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Refraction

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Quantum Physics

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Wave-Particle Duality

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Deformation of Solids

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Thermal Physics

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The Nucleus and Radioactive Decay

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Gravitational Fields

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Electric Fields

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Capacitors

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Magnetic Fields

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Fundamental Particles

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Quantum Physics

Energy levels in atoms

3 things to know
Unit AS 2

Overview

Energy level in an atom, ground state of an atom and excited state.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is meant by an energy level in an atom?

Key term

Why are atomic energy levels given negative values?

Key term

What is the ground state of an atom?

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by an energy level in an atom?
Model answer
An energy level is one of the definite, discrete values of energy that an electron in an atom is allowed to have, with no values in between permitted.
2
What is the evidence that electron energies in an atom take only certain values?
Model answer
Gases emit and absorb light only at a set of sharply defined wavelengths characteristic of the element, which can only happen if the energy changes available to their electrons are themselves restricted to particular values.
3
Why are atomic energy levels given negative values?
Model answer
The zero of energy is taken as an electron just free of the atom and at rest, so an electron that is bound has less energy than that and its value is negative.
4
What is the ground state of an atom?
Model answer
The ground state is the arrangement in which the electrons occupy the lowest available energy levels, so the atom has its lowest possible total energy.
5
What is an excited state?
Model answer
An excited state is any arrangement in which an electron has been raised to a higher energy level than it would occupy in the ground state.
6
How can a photon excite an atom, and what condition must the photon satisfy?
Model answer
The photon is absorbed and lifts an electron to a higher level, but only if its energy exactly matches the difference between two levels, because the electron cannot end up anywhere in between.

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