a) Determine the core charge and valence shell for \(\mathrm{Na}\) and \(\mathrm{Na}^{+}\). Drawing diagrams may be helpful. b) Based on your answer to part a, from which species will it be easier to remove an electron: Na or \(\mathrm{Na}^{+}\). Explain your reasoning clearly. c) The ions formed in molecules from Group 1 atoms (the alkali metals, such as \(\mathrm{Na}\) ) are almost exclusively \(\mathrm{M}^{+}\) ions rather than \(\mathrm{M}^{2+}\) ions. Explain this result based on your answers to parts a and b.

The concept of core charge is fundamental to understanding how atoms interact and form ions. It's the effective charge that an electron in the outermost shell experiences from the nucleus, after accounting for the shielding effect of the electrons in the inner shells. For sodium (Na), with 11 protons in its nucleus, the core charge is +11. This remains the same for the sodium ion (\(Na^{+}\)), as removing an electron does not change the number of protons.

The core charge helps to explain the forces within an atom that impact its reactivity. The higher the core charge, the greater the attractive force on the valence electrons, which typically leads to a greater tendency to attract additional electrons or a higher energy required to remove an electron.

• Sodium (Na) core charge: +11
• Sodium ion (\(Na^{+}\)) core charge: +11

Valence shells are crucial in the context of chemical reactivity, since the electrons in these shells can be gained, lost, or shared during chemical reactions, leading to the formation of chemical bonds. In sodium (Na), the valence shell is its third and outermost shell.

For the neutral sodium atom and the sodium ion (\(Na^{+}\)), the valence shell is the same. However, the removal of an electron when forming the sodium ion changes the electron configuration, leaving a full second shell that mirrors the stable configuration of the noble gases, showcasing the importance of a completed valence shell in achieving stability.

• Neutral Sodium (Na) valence shell: 3rd
• Sodium ion (\(Na^{+}\)) valence shell: Completed 2nd (after electron removal)

Electron removal energy, also known as ionization energy, is the amount of energy required to remove an electron from an atom or ion. In general, the closer an electron is to the nucleus and the higher the core charge, the more energy it takes to remove that electron.

When comparing a neutral sodium atom with the sodium ion, the neutral atom has a lower electron removal energy because its valence electron is further from the nucleus and experiences less attractive force due to lesser effective nuclear charge. In contrast, the sodium ion, having lost an electron, holds onto its remaining electrons more tightly, increasing the required energy to remove another electron.

• Neutral Sodium (Na) electron removal: lower energy
• Sodium ion (\(Na^{+}\)) electron removal: higher energy

Alkali metals, found in Group 1 of the periodic table, are known for their singular valence electrons and high reactivity. These metals, which include lithium, sodium, and potassium among others, react by losing their one valence electron to form +1 ions, achieving a stable electronic configuration.

The alkali metals are characterized by their low electron removal energy for the first valence electron due to its distance from the nucleus and the relatively low core charge experienced. This reactivity is the reason why alkali metals are rarely found in their pure elemental form in nature, as they readily form compounds with other elements, particularly halogens.

• Common property of Alkali metals: one valence electron
• Typical ion formed: \(M^{+}\) ion

A stable electronic configuration approximately means that an atom has a filled valence shell, which is typically associated with the noble gases, such as helium, neon, and argon. For Group 1 elements, achieving this stable configuration involves losing one electron, ending up with a full outer shell from the previous energy level.

By adopting this configuration, Group 1 elements minimize their potential energy, adhering to the principle that systems tend to the most stable, low-energy state. This explains why alkali metals form \(M^{+}\) ions, as it's energetically unfavorable to lose the additional electron from the stable configuration to form \(M^{2+}\) ions.

• Stability achieved by: Completing valence shell
• Result for Group 1 elements: Formation of \(M^{+}\) ions