Question

In isoclectronic cations, ion having more nuclear charge has the size (1) higher (2) smaller (3) equal (4) cannot be determined

Short answer

Smaller (2)

Step-by-step solution

- Understanding Isoelectronic Cations

Identify what is meant by isoelectronic cations. Isoelectronic cations are ions that have the same number of electrons but different numbers of protons (nuclear charge).

- Concept of Nuclear Charge

Understand the effect of nuclear charge on the size of the ion. Higher nuclear charge means more protons in the nucleus, which leads to a stronger attraction between the nucleus and the electrons.

- Correlation between Nuclear Charge and Ion Size

Explain that increasing the nuclear charge while keeping the number of electrons the same results in a smaller ion size. This is because the electrons are pulled closer to the nucleus with a stronger attraction.

- Conclusion from Understanding

Conclude that among isoelectronic cations, the ion with the higher nuclear charge will have the smaller size.

Key concepts

Nuclear Charge

Nuclear charge refers to the total positive charge of the nucleus, which is equal to the number of protons. This charge exerts a force on the electrons orbiting the nucleus. The more protons there are in the nucleus, the higher the nuclear charge. This causes a stronger attraction between the nucleus and the electrons.

In isoelectronic cations (ions with the same number of electrons), the ions still have different nuclear charges because they have different numbers of protons. Understanding how nuclear charge affects ion properties helps us determine differences in ion size.

Ion Size

Ion size, or ionic radius, depends on the balance between the nuclear charge and the electron repulsion forces. When dealing with isoelectronic cations, they all have the same number of electrons. Therefore, nuclear charge becomes the critical factor.

Higher nuclear charge pulls the electrons more strongly towards the nucleus. This causes the electrons to be held more tightly and reduces the size of the ion. Conversely, a lower nuclear charge results in a weaker pull on the electrons, allowing them to occupy a larger space and increase the size of the ion.

To summarize, among isoelectronic cations, the one with the higher nuclear charge will inevitably be smaller in size due to the stronger attractive force from the nucleus.

Electron Attraction

Electron attraction is the force that pulls electrons towards the nucleus. This force is stronger when the nuclear charge is higher. Understanding electron attraction is key to explaining why ions with higher nuclear charges are smaller, even if they have the same number of electrons as others.

The principle behind this is Coulomb's Law, which states that opposite charges attract each other. In an atom or ion, the positive nuclear charge attracts the negatively charged electrons. Higher nuclear charge means a stronger attraction, pulling the electrons closer and resulting in a smaller ion size.

In essence, for isoelectronic cations, higher electron attraction (due to higher nuclear charge) directly correlates to a smaller ionic radius.