The question asks about the number of electrons in a hydrogen atom in its ground state, given its orbital configuration as \(1s^1\). We need to understand the notation of electron configurations to determine the number of electrons.
Correct Option: B) One
The notation \(1s^1\) explicitly states that there is one electron (\(x=1\)) in the \(1s\) orbital. For a hydrogen atom in its ground state, this is the complete electron configuration, meaning it has a total of one electron.
The question asks about the characteristic of hydrogen that makes it resemble alkali metals (Group 1 elements). This resemblance is primarily due to its electronic configuration and its tendency to form a cation by losing valence electrons. We need to determine the number of valence electrons hydrogen possesses.
C) One — Hydrogen has one proton and one electron. This single electron is its valence electron, located in the 1s orbital. Like alkali metals, hydrogen can lose this one valence electron to form a cation (\(H^+\)).
The question asks why hydrogen resembles halogens, specifically in terms of electron gain to achieve a stable noble gas configuration. To answer this, we need to recall the electronic configuration of hydrogen and the general characteristic of halogens regarding electron gain.
Therefore, hydrogen needs to gain one electron to attain a stable noble gas configuration, which is similar to halogens.
Correct Option: C) One — Hydrogen has 1 electron and needs to gain 1 more electron to achieve the stable duplet configuration of Helium (\(1s^2\)). Halogens also need to gain 1 electron to complete their octet.
The question asks to identify a property where hydrogen significantly differs from alkali metals, despite being placed in Group 1. We need to compare the given properties (atomic radius, ionization enthalpy, density, melting point) of hydrogen with those of alkali metals.
Correct Option: B) Ionisation enthalpy
Hydrogen has a very high ionization enthalpy (\(1312 \text{ kJ/mol}\)) compared to alkali metals (e.g., Lithium: \(520 \text{ kJ/mol}\), Sodium: \(496 \text{ kJ/mol}\)). This is because its single electron is very close to the nucleus and is not shielded by any inner electron shells, making it difficult to remove.
The question asks for the approximate ionisation enthalpy of hydrogen. Ionisation enthalpy is the energy required to remove an electron from a gaseous atom in its ground state. For hydrogen, this corresponds to removing the single electron from the 1s orbital.
C) 1312 kJ/mol is the correct approximate ionisation enthalpy of hydrogen, derived directly from the energy of the electron in the ground state of a hydrogen atom.
The question asks for the name of the negatively charged ion formed when hydrogen gains an electron, similar to how halogens form anions. We need to identify the correct term among the given options.
Correct Option: D) Hydride ion (H⁻)