Bonding Yr1 Flashcards
(41 cards)
What is the main factor affecting the size of Van der Waals forces?
The number of electrons in the molecule. The more electrons, the stronger the Van der Waals forces and the higher the boiling point.
What is the shape of a molecule with linear geometry?
A molecule with linear geometry has a bond angle of 180 degrees.
Define octahedral geometry.
Octahedral geometry refers to a molecular shape with six bond pairs and no lone pairs, resulting in bond angles of approximately 90 degrees.
How can you determine the shape of a molecule with trigonal bipyramidal geometry?
A molecule with trigonal bipyramidal geometry has bond angles of approximately 119 degrees and 89 degrees.
Describe the shape of a molecule with a lone pair that reduces the bond angle.
The presence of a lone pair in a molecule can reduce the bond angle, resulting in a shape that deviates from the expected angle.
What is electronegativity?
Electronegativity is the relative tendency of an atom in a covalent bond to attract electrons in a covalent bond to itself.
Describe the factors affecting electronegativity.
Electronegativity increases across a period as the number of protons increases and the atomic radius decreases. It decreases down a group because the distance between the nucleus and the outer electrons increases and the shielding of inner shell electrons increases.
What is intermediate bonding?
Ionic and covalent bonding are the extremes of a continuum of bonding type. Differences in electronegativity between elements can determine where a compound lies on this scale.
How is a polar covalent bond formed?
A polar covalent bond forms when the elements in the bond have different electronegativities (around 0.3 to 1.7).
What determines if a molecule is polar or non-polar?
A symmetric molecule with all identical bonds and no lone pairs will not be polar. If the individual dipoles on the bonds cancel out due to the symmetrical shape of the molecule, it is non-polar.
Describe Van der Waals’ forces.
Van der Waals’ forces occur between all molecular substances and noble gases. They are transient, induced dipole-dipole interactions that form due to fluctuating electron density in molecules.
Describe the shape of a molecule with square planar geometry.
The molecule has a square planar shape with bond angles of approximately 90 degrees.
Define permanent dipole-dipole forces.
Permanent dipole-dipole forces occur between polar molecules. They are stronger than Van der Waals forces and result from a significant difference in electronegativity between atoms.
How do the boiling points of halogens change down the group?
The boiling points increase down the group due to the increasing number of electrons in the bigger molecules, resulting in larger Van der Waals forces.
Describe hydrogen bonding.
Hydrogen bonding occurs in compounds with a hydrogen atom attached to nitrogen, oxygen, or fluorine. These compounds must also have an available lone pair of electrons.
What causes the anomalously high boiling points of H2O, NH3, and HF?
The hydrogen bonding between the molecules causes the high boiling points.
Explain the general increase in boiling point from H2S to H2Te.
The increase in boiling point is caused by increasing Van der Waals forces between molecules due to an increasing number of electrons.
What are the four types of crystal structure?
The four types of crystal structure are ionic, metallic, molecular, and giant covalent (macromolecular).
Describe the structure of an ionic crystal.
An ionic crystal has a giant ionic lattice showing alternate Na+ and Cl- ions.
Describe the structure of a metallic crystal.
A metallic crystal has a giant metallic lattice showing close packing magnesium ions.
Describe the structure of a molecular crystal.
A molecular crystal, like ice, has regular arrangement of water molecules held together by weak van der Waals forces.
Describe the structure of a macromolecular crystal.
A macromolecular crystal, like diamond or graphite, has a giant structure with strong covalent forces and delocalized electrons.
Define metallic bonding.
Metallic bonding is the electrostatic force of attraction between positive metal ions and the delocalized electrons.
What happens to metal atoms during ionic bonding?
Metal atoms lose electrons to form positive ions.
