1A.3 Atomic Spectra

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1A.3 Atomic Spectra

Postby keyaluo4C » Sun Oct 14, 2018 7:38 pm

Can someone explain this portion of the textbook to me?

"When an electric current is passed through a low-pressure sample of hydrogen gas, the gas emits light. Hydrogen gas itself does not conduct electricity, but a strong electric field strips off electrons from the H2 molecules. As a result, they fall apart to form a “plasma” of H+ ions and electrons, which conduct the current. The electrons almost immediately reattach to the
H+ ions to form energetically excited hydrogen atoms. "

What does it mean for the electrons to fall apart and form a plasma? Why are does reattaching electrons to H+ ions form energetically excited hydrogen atoms?

Michael Torres 4I
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Re: 1A.3 Atomic Spectra

Postby Michael Torres 4I » Sun Oct 14, 2018 8:01 pm

Plasma is defined as being an ionized gas consisting of free electrons and positive ions. Plasma is created when a gas is exposed to high temperatures, or as would occur in this case, an electrical current. Because the current makes the atoms in the gas move very quickly, the electrons get knocked out of their orbit with the hydrogen atoms. This would occur with high temperatures, too.

When the electrons reattach to the H+ ions they are excited because they have been knocked out of their orbits and have energy that was imparted onto them by the electricity. This energy is released as electromagnetic radiation when electrons fall back down to their ground state and return to their orbits, but they are temporarily at an excited state before that happens.

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Re: 1A.3 Atomic Spectra

Postby arif_latif_2G » Sun Oct 14, 2018 8:10 pm

I am assuming that when they said, "Fall apart," it meant that the H2 gas separates into 2H+ and 2e-. Since the gas becomes ionized, they called it a plasma.
It requires a lot of energy to remove the single electron from a hydrogen atom. The electron gains a lot of energy in order for it to separate in the first place, but since the e- and H+ ion are attracted to one another, they come back to form a regular Hydrogen atom, but since the e- had a lot of energy, when they combined, the newly formed Hydrogen atom becomes "energetically excited," meaning to say that electron is at not at ground state and has more energy than it should, making the atom "excited."

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