Chemical Bonding And Molecular Structure

Step 1: Definition of a dipole moment.
A dipole moment arises when there is a separation of positive and negative charge centers in a molecule.
Step 2: Polar vs Non-polar.
- Polar materials have a permanent dipole moment due to asymmetric charge distribution (e.g., ).
- Non-polar materials have no permanent dipole moment, where the centers of positive and negative charges coincide (e.g., ).
Step 3: Conclusion.
Molecules with a permanent dipole moment are called polar materials.
Final Answer:

Step 1: Prokaryotic genome features.
- DNA is usually circular, double-stranded.
- DNA lacks histones (except in some archaea).
- Genes are often organized into operons.
Step 2: Eukaryotic genome features.
- DNA is linear and associated with histones.
- Genes contain introns (intervening sequences) that require splicing.
Step 3: Conclusion.
The main distinguishing feature is the presence of intervening sequences (introns) in eukaryotic DNA.
Final Answer:

Step 1: Recall orbital overlap condition.
Effective overlap occurs when orbitals are aligned along the internuclear axis (the line joining two nuclei).
Step 2: Application to s and p orbitals.
- The spherical s-orbital can overlap with a p-orbital lobe only if the lobe points along the axis joining the nuclei.
- If perpendicular, acute, or obtuse angle → poor or zero overlap.
Final Answer:

Step 1: Recall electronegativity concept.
- A highly electronegative element (e.g., Cl, O) tends to gain electrons.
- An electropositive metal (e.g., Na, K, Ca) tends to lose electrons.
Step 2: Bond formed.
The electron transfer leads to the formation of cations (from metal) and anions (from non-metal), producing an ionic compound.
Step 3: Eliminate other options.
- Interstitial alloy: small atoms occupy voids in metal lattice (not the case here).
- Substitutional alloy: one metal substitutes another in a lattice (metal-metal combination).
- Simple mixture: no chemical bonding.
Final Answer:

Step 1: Recall molecular geometries.
- XeF : Square planar (due to 2 lone pairs on Xe).
- BF : Trigonal planar ( -hybridized).
- BCl : Trigonal planar ( -hybridized).
- PCl , NCl : Trigonal pyramidal (due to lone pairs) → not planar.
- XeF : Distorted octahedral → not planar.
Step 2: Correct combination.
Only option (4) has all planar species: XeF , BF , BCl .
Final Answer: