Group 18 Elements

Step 1: Understanding the Concept:
Electron gain enthalpy is the energy released when an electron is added to a neutral gaseous atom. For inert gases, this process is highly endothermic (positive) because the added electron must go into a new, higher-energy shell.

Step 2: Detailed Explanation:
Among the noble gases, the value of positive electron gain enthalpy decreases as we go down the group. This is because the atomic size increases, and the added electron can be accommodated more easily in a larger, more diffuse orbital. Helium has a very small size, so adding an electron is extremely difficult. Neon, being the next smallest, also has a very high positive electron gain enthalpy. However, the trend generally shows that the smallest atom has the most positive value. But among the options, Neon is known to have an exceptionally high positive value due to its stable, compact electronic configuration.

Step 3: Final Answer:
Neon (Ne) has the largest positive electron gain enthalpy among the given inert gases.

Step 1: Understanding the Concept:
Elements with atomic numbers greater than 100 have systematic IUPAC names based on their atomic number digits.

Step 2: Detailed Explanation:
The IUPAC name for element with atomic number 105 is Dubnium (Db). The naming is as follows:
• 104: Rutherfordium (Rf)
• 105: Dubnium (Db)
• 106: Seaborgium (Sg)
• 107: Bohrium (Bh)
• 108: Hassium (Hs)
• 109: Meitnerium (Mt)

Step 3: Final Answer:
The IUPAC name of element with atomic number 105 is Dubnium.