Na+ and Se2-

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Na+ and Se2- are ions that have formed due to the transfer of electrons between sodium (Na) and selenium (Se) atoms.

1. Sodium (Na) has 11 electrons in its neutral state, arranged in the electron configuration 1s2 2s2 2p6 3s1.

2. In order to achieve a stable electron configuration, sodium needs to lose one electron. This results in the formation of a sodium ion with a charge of +1, written as Na+.

3. Selenium (Se) has 34 electrons in its neutral state, arranged in the electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4.

4. To achieve a stable electron configuration, selenium needs to gain two electrons. This results in the formation of a selenium ion with a charge of -2, written as Se2-.

In summary, Na+ has lost one electron to achieve a stable configuration, while Se2- has gained two electrons to achieve a stable configuration. These ions have opposite charges and are attracted to each other, forming an ionic bond.

Na+ and Se2- refer to the ions of sodium and selenium, respectively. Sodium (Na) is a metal that tends to lose one electron to achieve a stable electron configuration like the noble gas neon. So, it loses an electron to form the sodium ion, Na+.

On the other hand, selenium (Se) is a nonmetal that tends to gain two electrons to achieve a stable electron configuration like the noble gas argon. So, it gains two electrons to form the selenium ion, Se2-.

To determine the charges of these ions, we need to consider their positions on the periodic table. Sodium is in Group 1, which means it has one valence electron, whereas selenium is in Group 16, having six valence electrons.

The valence electrons of sodium are relatively far from the nucleus, so it is easier for sodium to lose one electron and become Na+. In comparison, selenium's valence electrons are closer to the nucleus and have a higher attraction, making it more likely to gain two electrons and become Se2-.

In summary, Na+ is a cation with a positive charge because it loses one electron, while Se2- is an anion with a negative charge because it gains two electrons.