Problem 107 - Chemistry The Central Science In Si Units

Question

In April 2010 , a research team reported that it had made Element 117 . This discovery was confirmed in 2012 by additional experiments. Write the ground- state electron configuration for Element 117 and estimate values for its first ionization energy, electron affinity, atomic size, and common oxidation state based on its position in the periodic table.

Step-by-Step Solution

Answer

Element 117 has an electron configuration of \[ [Rn]7s^2 5f^{14} 6d^{10} 7p^5 \]. It likely has lower ionization energy and electron affinity than astatine, larger atomic size, and oxidation states of -1 and possibly +1 or +3.

Step 1: Determine the Electron Configuration

Element 117 is known as Tennessine (Ts) and is part of the halogen group in the periodic table. It is located in the 7th period and group 17. To find its ground-state electron configuration, consider that the last filled orbit before it reaches Element 118 (the noble gas) will be the 7p orbitals. Following the periodicity:1. Start at the closest preceding noble gas which is Radon (Rn): [Rn].2. Fill the 7s orbital: [Rn]7s².3. Fill the 5f orbital (14 electrons): [Rn]7s²5f¹⁴.4. Next, fill the 6d orbitals (10 electrons): [Rn]7s²5f¹⁴6d¹⁰.5. Finally, add 5 electrons to the 7p orbital: [Rn]7s²5f¹⁴6d¹⁰7p⁵.Thus, the ground-state electron configuration for Element 117 is \[[Rn]7s^2 5f^{14} 6d^{10} 7p^5. \]

Step 2: Estimate the First Ionization Energy

Element 117 is a halogen, and as such, halogens typically have high first ionization energies due to their nearly complete p orbitals, which provide stability. However, since Element 117 is further down the group, relativistic effects and increased shielding will lower the ionization energy compared to lighter halogens like iodine. Its first ionization energy is likely to be slightly lower than that of astatine, which is above it in the same group.

Step 3: Predict the Electron Affinity

Again, as a halogen, Element 117 should exhibit a high electron affinity, as halogens tend to readily gain an electron to fill their outer p orbital. However, due to its increased atomic size and relativistic effects, its electron affinity is expected to be lower than that of lighter halogens, perhaps similar to or a bit lower than that of astatine.

Step 4: Assess Atomic Size

Atomic size increases as you move down a group in the periodic table due to the addition of electron shells. Therefore, Element 117 will have a larger atomic size than astatine, the halogen above it. The exact size is difficult to predict but will be larger than the other halogens due to its position in the 7th period.

Step 5: Determine Common Oxidation States

Typically, halogens exhibit an oxidation state of -1 as they tend to gain an electron to complete their p orbitals. However, for heavier halogens such as Element 117, the +1, +3, or even higher oxidation states may be more stable due to the inert pair effect and relativistic stabilization of the s orbitals. Thus, while -1 is common, expect possible higher oxidation states.

Key Concepts

Electron Configuration

When it comes to understanding the electron configuration of Element 117, also known as Tennessine (Ts), it helps to remember where it is positioned on the periodic table. Tennessine is in the 7th period and group 17, which places it among the halogens.

To find its ground-state electron configuration, we begin by identifying the most recent noble gas before Element 117, which is Radon (Rn). This provides us a handy shorthand:

• Start with the Radon core: \([Rn]\)
• Add the 7s electron pair: \([Rn] 7s^2\)
• Fill up the 5f orbitals with 14 electrons: \([Rn] 7s^2 5f^{14}\)
• Next comes the 6d orbitals with 10 electrons: \([Rn] 7s^2 5f^{14} 6d^{10}\)
• Finally, add five electrons to the 7p orbital: \([Rn] 7s^2 5f^{14} 6d^{10} 7p^5\)

Thus, the electron configuration of Tennessine, taking into account shell filling order, ends at the 7p orbital, making its configuration: \[[Rn] 7s^2 5f^{14} 6d^{10} 7p^5.\]

Ionization Energy

Ionization energy refers to the energy needed to remove an electron from an atom. For halogens like Element 117, high ionization energies are typical because their p orbitals are nearly full, contributing to their stability. However,

as we move further down the group to heavier elements like Tennessine, some changes occur:

• Relativistic effects: The increased speed of orbiting electrons affects ionization energy.
• Shielding Effect: Electrons further out are shielded from the nucleus's pull by inner electrons, reducing ionization energy.

Therefore, although Tennessine will have a high ionization energy due to its group, expect it to be slightly lower than Astatine (At), the halogen directly above it on the periodic table.

These factors demonstrate how both periodic trends and relativistic influences impact ionization energies in these superheavy elements.

Atomic Size

Atomic size, or atomic radius, refers to the distance from the atom's nucleus to the boundary of its surrounding cloud of electrons. For elements within the same group, the trend is:

• Atomic size increases as you move down the group due to the addition of electron shells.
• Each additional filled shell increases distance between the nucleus and the outermost shell.

In the case of Tennessine, being in the 7th period means it has more shells than Astatine and other lighter halogens, resulting in a larger atomic size.

While predicting the exact size is complex due to relativistic effects and electron cloud diffusions, it is safe to say Tennessine's atomic size will be greater than any halogen preceding it. Knowing this helps in estimating the behavior and reactivity of this synthetic element.

Oxidation States

Understanding oxidation states involves predicting how many electrons an element will gain, lose, or share during chemical reactions. For halogens, a common oxidation state is -1, due to their tendency to gain an electron and fill their p orbitals.

Tennessine, however, introduces complexity due to:

• Relativistic Effects: Can alter expected chemical behavior.
• Inert Pair Effect: Makes certain oxidation states more stable as you move down the group.

Therefore, while -1 is possible, Tennessine might exhibit higher states like +1 or +3, making it distinct among halogens. These higher oxidation states arise because the 7s electrons can become inert and less involved in bonding, stabilizing alternative electron counts.

This expanded range of oxidation states showcases the unique chemistry of superheavy elements compared to their lighter counterparts.