Question

The \(\mathrm{Na}^{+}\) ion and the Ne atom are isoelectronic. The ease of loss of an electron by a gaseous Ne atom, \(I_{1}\) has a value of \(2081 \mathrm{kJ} / \mathrm{mol} .\) The ease of loss of an electron from a gaseous \(\mathrm{Na}^{+}\) ion, \(I_{2}\), has a value of \(4562 \mathrm{kJ} / \mathrm{mol} .\) Why are these values not the same?

Short answer

The difference in Ionization energy between Na+ and Ne, even though they are isoelectronic, arises due to the difference in nuclear charge they have. Sodium Ion Na+ has a higher nuclear charge than Neon, so it has a stronger hold on its electrons. Additionally, removing an electron from Na+ would mean losing an electron from a lower energy level which is closer to the nucleus, thus needs more energy.

Step-by-step solution

Understand the Properties of Neon and Sodium Ion

Both Ne and Na+ have the same number of electrons, which is 10. Therefore, they are isoelectronic. However, they are not the same atom and they don't have the same number of protons in their nucleus which affects the ionization energy.

Understand Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion in its gaseous state. The ionization energy depends on the attraction between the electrons and the nucleus. If an atom has a larger nuclear charge, the electrons will be more attracted to the nucleus, requiring more energy to be removed. That's why \(I_{1}\) for Ne is 2081 kJ/mol and \(I_{2}\) for Na+ is 4562 kJ/mol.

Compare the Ionization Energies of Neon and Sodium Ion

Neon atom has a nuclear charge of +10 (since it has 10 protons), while sodium ion Na+ also has a nuclear charge of +11 (since it has 11 protons). The additional proton in sodium ion leads to a greater attractive force on the electrons. That's why the ionization energy of sodium ion is higher than that of Neon.

Understand the Difference in Ionization Energies

When we're removing the first electron from Neutral Neon, that electron is being removed from a shell that is already stable (complete shell). However, for sodium ion Na+, when the second electron is being removed, it's being removed from a lower energy level which is closer to the nucleus and hence under a much greater attractive force. This is why it takes more energy to remove an electron from Na+ than it does from Ne.

Key concepts

Isoelectronic Species

Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. As a result, they share a similar electronic structure. This makes them interesting in chemistry because even though they have a similar number of electrons, their chemical properties can differ significantly.

In our example, the sodium ion (\(\mathrm{Na}^+\)) and the neon atom (Ne) both have 10 electrons each. They are therefore isoelectronic. However, despite this similarity, they are not the same atom. This is because having the same number of electrons doesn't mean having the same positive charge in the nucleus.

• The sodium ion has shed an electron to become positively charged, while the neon remains neutrally charged.
• Their different nuclear charges impact the overall stability and interactions of their electrons.

Thus, while isoelectronic species may look similar in terms of their electron configuration, their behavior and chemical properties can be quite different due to factors like nuclear charge.

Atomic Structure

Atomic structure is the arrangement of electrons, protons, and neutrons within an atom. This structure defines the atom's properties and behavior.

Atoms consist of a nucleus made up of protons and neutrons, surrounded by electrons in various energy levels or shells. Protons have a positive charge, electrons have a negative charge, and neutrons are neutral.

• The atomic number, which is the number of protons, defines the element.
• The neutron count can change to create isotopes of the same element.
• The electron configuration impacts the chemical properties and reactivity of the element.

The distribution of these particles dictates calls to action like ionization energy, which is crucial when comparing atoms such as sodium ion (\(\mathrm{Na}^+\)) and neon (Ne).

The difference in these two species arises from their atomic structure:1. \(\mathrm{Na}^+\) has a nucleus with 11 protons, giving it a higher nuclear charge compared to Neon's 10 protons.2. This results in stronger coulombic attraction between the nucleus and the electrons in \(\mathrm{Na}^+\) than in Ne, impacting various properties such as ionization energy.

Nuclear Charge

Nuclear charge refers to the total charge of the protons in an atom's nucleus, which influences how strongly the nucleus attracts electrons. The nuclear charge is pivotal in understanding the ionization energy, especially when comparing isoelectronic species.

For example, in our problem, neon (Ne) and sodium ion (\(\mathrm{Na}^+\)) are both considered. Despite having the same number of electrons, \(\mathrm{Na}^+\) has one more proton than Ne. This extra proton increases the nuclear charge, making it +11 for sodium ion compared to +10 for neon.

The higher the nuclear charge:

• The stronger the pull on electrons, making them more tightly bound to the nucleus.
• This increases the energy required to remove an electron, therefore raising the ionization energy.

As a result, \(\mathrm{Na}^+\) has a higher ionization energy than Ne, requiring more energy to remove an electron, thus explaining the discrepancy in their ionization energies. Understanding nuclear charge is essential to comprehending the interactions within an atom and how it influences atomic properties like ionization energy.