Based on the trends you've identified, what generalizations can you make about how atoms gain or lose electrons? Select all the correct answers.

1. Atoms with close to eight valence electrons tend to gain electrons when forming ions.

2. Atoms with only a few valence electrons tend to lose electrons when forming ions.

3. Atoms tend to gain or lose electrons such that they have eight valence electrons.

4. Atoms tend to gain or lose electrons in a way that results in the same electron configuration as a noble gas.

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Explanation:

Atoms tend to gain or lose electrons to obtain the same electron configuration as a noble gas. So, the resulting ions have two electrons in the last s sublevel and six electrons in the last p sublevel, giving a total of eight valence electrons. A metal atom has only a few valence electrons, so it loses all of its valence electrons. The loss of valence electrons gives the metal atom the electron configuration of the noble gas in the previous period. A nonmetal atom has more valence electrons, so it gains enough electrons to have eight. The gain in valence electrons gives the nonmetal atom the electron configuration of the noble gas at the end of its period.

Atmospheric pressure is measured with a barometer. A barometer consists of an evacuated vertical tube with its top end closed and its bottom end resting in a container of mercury that is open to the atmosphere The pressure exerted by the atmosphere acts on the exposed surface of the liquid to force mercury up into the tube. Sea level atmospheric pressure will support a mercury column generally not more than 29.92-in. high. Thus, the standard for atmospheric pressure at sea level is 29.92 in.-Hg, which translates to an absolute pressure of 14.69 psia.
The two basic reference points in all these measurements are standard atmospheric pressure and a perfect vacuum.