Problem 107 - Chemistry The Central Science

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 afnity, atomic size, and common oxidation state based on its position in the periodic table.

Step-by-Step Solution

Answer

Element 117, Tennessine (Ts), has a ground-state electron configuration of \([Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{5}\). Its first ionization energy is expected to be high, slightly lower than Astatine. Tennessine's electron affinity should be high, also similar to that of other halogens. Its atomic size is likely larger than Astatine, and Ts's common oxidation state is predicted to be -1.

Step 1: Ground-state electron configuration

To determine the ground-state electron configuration of Tennessine, follow the periodic table and fill the electron orbitals as per the Aufbau principle until you reach Element 117. The electron configuration will be: \[ [Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{5} \] This configuration shows that Element 117 has filled 5f and 6d orbitals, two electrons in the 7s orbital, and five electrons in the 7p orbital.

Step 2: Estimate the first ionization energy

The first ionization energy is the energy required to remove one electron from an atom to form a positive ion. As we move across a period, the ionization energy generally increases due to the increased effective nuclear charge. Since Tennessine is in Group 17, it should have a higher ionization energy compared to the elements to its left, but lower than that of the noble gases in Group 18. We can estimate that the first ionization energy of Tennessine will be slightly less than that of Astatine (At), the halogen in Period 6.

Step 3: Estimate the electron affinity

Electron affinity is the energy change when an electron is added to an atom to form a negative ion. Electron affinity generally increases across a period due to the increased effective nuclear charge. Halogens have high electron affinity since their addition of an electron results in a complete outer energy level. We can expect Tennessine to have a high electron affinity, similar to other halogens, and possibly slightly lower than Astatine's electron affinity.

Step 4: Estimate the atomic size

The atomic size generally increases as we move down a group due to the addition of electron shells, leading to increased shielding and a larger atomic radius. Tennessine is the heaviest halogen, and we can expect that its atomic size will be larger than that of Astatine, the halogen in Period 6.

Step 5: Determine the common oxidation state

The common oxidation state for an element can be predicted based on its group number and the number of valence electrons it possesses. Halogens, including Tennessine, typically have an oxidation state of -1 due to their high affinity for electrons. They can gain one electron in chemical reactions to achieve a complete outer energy level resembling the noble gases. In summary, Element 117 (Tennessine) has the ground-state electron configuration of [Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{5}, high ionization energy, high electron affinity, a large atomic size compared to the other halogens, and a common oxidation state of -1.

Key Concepts

Ground-state electron configuration

The ground-state electron configuration is crucial to understanding how electrons are arranged in an atom. For Tennessine (Element 117), it follows the order in the periodic table, adding electrons into the appropriate orbitals based on energy level. According to the Aufbau principle, electrons fill the lowest energy orbitals available before moving to higher ones. So, the electron configuration for Tennessine is:\[ [Rn] 5f^{14} 6d^{10} 7s^{2} 7p^{5} \]This notation tells us a few important things:

• The "[Rn]" part denotes that it has the same inner core electron configuration as Radon, which is a noble gas.
• The numbers and letters indicate the distribution of electrons across various shells and subshells.
• "5f^{14}", "6d^{10}", "7s^{2}", and "7p^{5}" represent electrons in different subshells, showing a completely filled 5f and 6d shell, a fully paired 7s orbital, and 5 electrons in the 7p shell.

First ionization energy

Ionization energy is the amount of energy needed to remove an electron from an atom, changing it to a positive ion. This energy is affected by:

• Electron shielding
• Atomic size
• Nuclear charge

For elements in Group 17 like Tennessine, the first ionization energy is higher than the elements on its left. This is due to a greater effective nuclear charge, which attracts the electrons strongly. However, it is lower than the noble gases in Group 18 due to their complete electron shells.
Estimating the first ionization energy of Tennessine places it slightly below Astatine, another Group 17 halogen from Period 6. This depends on it having similar but slightly weaker nuclear effects than Astatine due to the addition of another electron shell.

Electron affinity

Electron affinity measures the energy change when an electron is added to a neutral atom, turning it into a negative ion. Elements with high electron affinity values efficiently attract additional electrons.

Tennessine, as a halogen, is expected to have a high electron affinity. This arises because adding an electron results in a nearly complete outer shell similar to those of noble gases. The effective nuclear charge increases across a period which typically raises electron affinity in Group 17.
Yet, its electron affinity will likely be somewhat lower than Astatine's due to increased shielding from filled subshells, which counteracts the nuclear charge's effect.

Atomic size

Atomic size or atomic radius is influenced by electron arrangement and nuclear charge. As you proceed down a group in the periodic table, atomic size typically increases. For Tennessine, this means it should be larger than Astatine, the halogen just above it in Group 17.
This increase in size is due to the following factors:

• New energy levels (or shells) that are added with each period increase.
• Increased shielding effect from the inner layers of electrons.
• A decrease in the effective nuclear charge felt by the outermost electrons.

Despite its large size relative to other halogens, the increased electron shell number contributes substantially to Tennessine's ultimate atomic dimensions.

Oxidation state

The oxidation state of an element tells us about the number of electrons it can gain or lose during a chemical reaction. For halogens like Tennessine, the common oxidation state is -1.
This state results from:

• Their tendency to gain one electron to fill their outermost p orbital.
• High electron affinity factor due to the half-full outer electron shell which seeks completion.

Halogens such as Tennessine often share this tendency, securing a stable electronic configuration akin to noble gases. This -1 oxidation state frequently appears in their compounds, where the halogen acts as an electron accepter.