3.4 Energy levels in atoms

1. 3.4 Energy levels in atoms Electrons in atoms Electrons are attracted to a positive nucleus by electrostatic force Electrons move about in allowed orbits or shells with different energy levels The lowest energy state of an atom is called its ground state When an atom in its ‘ground’ state absorbs energy, one of its electrons moves to a shell at higher energy. The atom is now in an ‘excited’ state leaving a vacancy in the shell.

2. 3.4 Energy levels in atoms Electrons in atoms Electrons are attracted to a positive nucleus by electrostatic force Electrons move about in allowed orbits or shells with different energy levels The lowest energy state of an atom is called its ground state When an atom in its ‘ground’ state absorbs energy, one of its electrons moves to a shell at higher energy. The atom is now in an ‘excited’ state leaving a vacancy in the shell.

3. 3.4 Energy levels in atoms Electrons in atoms Electrons are attracted to a positive nucleus by electrostatic force Electrons move about in allowed orbits or shells with different energy levels The lowest energy state of an atom is called its ground state When an atom in its ‘ground’ state absorbs energy, one of its electrons moves to a shell at higher energy. The atom is now in an ‘excited’ state leaving a vacancy in the shell.

4. 3.4 Energy levels in atoms Electrons in atoms Electrons are attracted to a positive nucleus by electrostatic force Electrons move about in allowed orbits or shells with different energy levels The lowest energy state of an atom is called its ground state When an atom in its ‘ground’ state absorbs energy, one of its electrons moves to a shell at higher energy. The atom is now in an ‘excited’ state leaving a vacancy in the shell.

5. 3.4 Energy levels in atoms Electrons in atoms Electrons are attracted to a positive nucleus by electrostatic force Electrons move about in allowed orbits or shells with different energy levels The lowest energy state of an atom is called its ground state When an atom in its ‘ground’ state absorbs energy, one of its electrons moves to a shell at higher energy. The atom is now in an ‘excited’ state leaving a vacancy in the shell.

6. De-excitation An excited atom is unstable and the vacancy in the shell is soon filled by an electron from an outer shell dropping to a lower energy level emitting a photon. De excitation of a mercury atom may proceed indirectly to the ground state via an intermediate state. 5.7 eV 4.9 eV O eV 0.8 eV photon 4.9 eV photon

7. De-excitation An excited atom is unstable and the vacancy in the shell is soon filled by an electron from an outer shell dropping to a lower energy level emitting a photon. De excitation of a mercury atom may proceed indirectly to the ground state via an intermediate state. 5.7 eV 4.9 eV O eV 0.8 eV photon 4.9 eV photon

8. De-excitation An excited atom is unstable and the vacancy in the shell is soon filled by an electron from an outer shell dropping to a lower energy level emitting a photon. De excitation of a mercury atom may proceed indirectly to the ground state via an intermediate state. 5.7 eV 4.9 eV O eV 0.8 eV photon 4.9 eV photon

9. De-excitation An excited atom is unstable and the vacancy in the shell is soon filled by an electron from an outer shell dropping to a lower energy level emitting a photon. De excitation of a mercury atom may proceed indirectly to the ground state via an intermediate state. 5.7 eV 4.9 eV O eV 0.8 eV photon 4.9 eV photon

10. Excitation using photons An electron in an atom can absorb an incident photon’s energy if the photons energy exactly matches the quantum of energy required for excitation.

11. Excitation using photons An electron in an atom can absorb an incident photon’s energy if the photons energy exactly matches the quantum of energy required for excitation.

12. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. IR 1546 nm Uv 217 nm UV 252 nm In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

13. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

14. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

15. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

16. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. IR 1546 nm Uv 217 nm UV 252 nm In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

17. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. IR 1546 nm Uv 217 nm UV 252 nm In the Starter (a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

18. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. IR 1546 nm Uv 217 nm UV 252 nm In the Starter (a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

19. Fluorescence The atoms of a fluorescent substance may get excited by incident uv light. These atoms then de-excite emitting visible light. IR 1546 nm Uv 217 nm UV 252 nm In the Starter (a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable

21. Fluorescence In the Starter ( a time delay switch): an electric current warms the filament electrodes. During the first second argon vapor in the starter conducts and warms up a bimetallic strip which bends and switches off the current flowing through the filament electrodes. The mains voltage then acts across the filament electrodes causing the gas to glow. http://home.howstuffworks.com/question337.htm/printable