Explanation

• The principal quantum number (n) indicates the main energy level or shell occupied by an electron.
• In hydrogen-like atoms, electron energy depends primarily on the principal quantum number.
• A higher value of n corresponds to a higher energy level.

Last verified on 27-10-2026

Explanation

• Paramagnetism mainly occurs due to the presence of unpaired electrons in atoms, ions, or molecules.
• Unpaired electrons have magnetic moments that can align with an external magnetic field, causing the substance to be attracted to the field.
• Substances with all electrons paired are generally diamagnetic, meaning they are weakly repelled by a magnetic field.

Last verified on 27-10-2026

Explanation

• A nitrogen atom has the electronic configuration 1s² 2s² 2p³.
• In the nitrogen molecule (N₂), the first bond is a sigma (σ) bond, formed by head-on overlap of p orbitals.
• The other two bonds are pi (π) bonds, formed by sideways or parallel overlap of p orbitals.
• Therefore, nitrogen has a triple bond consisting of one sigma bond and two pi bonds.

Last verified on 27-10-2026

Explanation

• The electronic configuration 2s¹, 2p⁵ contains six electrons in the second shell.
• This configuration is higher in energy than the ground-state configuration 2s², 2p⁴ of oxygen.
• A species in a higher-energy state may release energy when it changes to a lower-energy, more stable state.

Last verified on 27-10-2026

Explanation

• Phosphorus (P), atomic number 15: Electronic configuration is [Ne] 3s² 3p³, with 3 unpaired electrons, one in each 3p orbital.

Additional information:

• Boron (B), atomic number 5: Electronic configuration is 1s² 2s² 2p¹, with 1 unpaired electron.
• Chlorine (Cl), atomic number 17: Electronic configuration is [Ne] 3s² 3p⁵, with 1 unpaired electron.

Last verified on 27-10-2026

Explanation

• Hydrochloric acid (HCl) is a strong acid, while barium hydroxide [Ba(OH)₂] is a strong base.
• When HCl is added to Ba(OH)₂, a neutralization reaction occurs: Ba(OH)₂ + 2HCl → BaCl₂ + 2H₂O
• The final concentration of hydrogen ions depends on the relative amounts of acid and base.
• If the added acid is insufficient to neutralize all the base, hydroxide ions remain in excess.
• If enough acid is added to exceed the neutralization point, hydrogen ions become excess.

Last verified on 27-10-2026

Explanation

• Magnesium has atomic number 12, so a neutral magnesium atom contains 12 electrons.
• Neon has atomic number 10 and contains 10 electrons.
• Magnesium loses two electrons to form Mg²⁺, which has 10 electrons, the same number as neon.
• The loss of electrons is called oxidation.
• Therefore, Mg²⁺ is isoelectronic with neon.

Last verified on 27-10-2026

Explanation

• A buffer solution resists sudden changes in pH when small amounts of acid or base are added.
• Sodium hydroxide (NaOH) is a strong base that increases the concentration of hydroxide ions (OH⁻).
• The added NaOH is neutralized partially by the acidic component of the buffer, but the pH generally increases slightly above 8.

Last verified on 27-10-2026

Explanation

• In an oxygen molecule (O₂), a π-bond is formed by the sidewise (parallel) overlap of two p-orbitals.
• A π-bond is formed by lateral overlap, with electron density above and below the internuclear axis.
• A sigma (σ) bond forms through head-on overlap of orbitals, whereas a pi (π) bond forms through sideways overlap.
• The O₂ molecule contains one sigma bond and one pi bond in its double bond.

Last verified on 27-10-2026

Explanation

• In the traditional valence-bond model, phosphorus in PCl₅ undergoes dsp³ (sp³d) hybridization.
• PCl₅ has a trigonal bipyramidal geometry, with three chlorine atoms in equatorial positions and two in axial positions.
• The three equatorial bonds are separated by 120°.
• While the axial bonds are at 90° to the equatorial bonds and 180° to each other.

Last verified on 27-10-2026