Chem

Question 1

What is electronegativity?

Answer 1

Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond.

Question 2

How does atomic size affect electronegativity?

Answer 2

Smaller atoms have higher electronegativity because their nucleus exerts a stronger pull on electrons. Larger atoms have lower electronegativity due to weaker nuclear attraction caused by increased distance and shielding.

Question 3

What is the effect of electron shielding on electronegativity?

Answer 3

Increased electron shielding (more inner electron shells) reduces electronegativity by weakening the effective nuclear charge felt by the outer electrons. This makes it harder for the atom to attract electrons.

Question 4

How does nuclear charge affect electronegativity?

Answer 4

A higher nuclear charge increases electronegativity because the stronger positive charge pulls electrons more effectively. More protons in the nucleus lead to a greater ability to attract electrons in a bond.

Question 5

What type of bond is formed when the electronegativity difference is less than 0.4?

Answer 5

A nonpolar covalent bond is formed, where electrons are shared equally between the atoms.

Question 6

What type of bond is formed when the electronegativity difference is between 0.4 and 1.8?

Answer 6

A polar covalent bond is formed, where electrons are shared unequally, creating partial charges on the atoms.

Question 7

What type of bond is formed when the electronegativity difference is greater than 1.8?

Answer 7

An ionic bond is formed, where electrons are completely transferred from one atom to another, resulting in positive and negative ions.

Question 8

Why do ionic bonds form between atoms with a large electronegativity difference?

Answer 8

When the electronegativity difference is large, the more electronegative atom fully pulls the electron from the less electronegative atom, creating ions that are attracted to each other due to opposite charges.

Question 9

What is covalent character in an ionic bond?

Answer 9

Covalent character in an ionic bond refers to the partial sharing of electrons between the cation and anion. This occurs when the positive ion pulls the electron cloud of the negative ion towards itself, making the bond behave more like a covalent bond than a purely ionic one.

Question 10

What factors increase covalent character in an ionic compound?

Answer 10

Covalent character increases when:

The cation is small and highly charged (high polarizing power).

The anion is large and easily distorted (high polarizability).

Question 11

What is a dipole moment?

Answer 11

A dipole moment is a measure of the separation of positive and negative charges in a molecule.

Question 12

What causes a dipole moment in a molecule?

Answer 12

A dipole moment is caused by a difference in electronegativity between atoms in a bond.

Question 13

Why does O₂ have no dipole moment?

Answer 13

O₂ has no dipole moment because the two oxygen atoms have equal electronegativity, so there is no charge separation.

Question 14

What is a nonpolar covalent bond?

Answer 14

A nonpolar covalent bond is when electrons are shared equally between two atoms with similar or identical electronegativities.

Question 14

Why does water (H₂O) have a dipole moment?

Answer 14

Water has a dipole moment because its bent shape causes the polar bonds to create a net separation of charges.

Question 15

What causes a polar covalent bond?

Answer 15

A polar covalent bond is caused by a difference in electronegativity between two atoms, leading to unequal sharing of electrons.

Question 16

How can you determine if a molecule is polar?

Answer 16

A molecule is polar if it has polar covalent bonds and its shape causes a net dipole moment, resulting in an uneven distribution of charge.

Question 17

What is bond energy?

Answer 17

Bond energy is the amount of energy required to break one mole of a specific type of bond in a gaseous molecule, converting the bonded atoms into isolated atoms.

Question 18

How does atomic size affect bond energy?

Answer 18

Larger atoms have longer bond lengths, resulting in lower bond energy because the bonding electrons are less attracted to the nuclei. Smaller atoms have shorter bond lengths and generally higher bond energy.

Question 19

What is the relationship between electronegativity difference and bond polarity?

Answer 19

A greater electronegativity difference between two atoms leads to a more polar covalent bond. Greater polarity usually results in higher bond energy.

Question 20

Why is the bond energy of F-F lower than the bond energy of Cl-Cl?

Answer 20

The F-F bond has lower energy due to high lone pair repulsion between the small fluorine atoms, despite the bond being short. The Cl-Cl bond is stronger because chlorine atoms are larger, leading to less repulsion and a longer bond.

Question 21

What is the typical trend in bond energy across a period in the periodic table?

Answer 21

Bond energy generally increases across a period from left to right due to decreasing atomic size and increasing effective nuclear charge, which results in stronger bonds.

Question 22

What is the basic principle of VSEPR theory?

Answer 22

Electron pairs around a central atom arrange themselves to minimize repulsion and maximize distance.

Question 23

How does VSEPR theory determine the shape of a molecule?

Answer 23

By counting the number of electron domains (bonding pairs and lone pairs) around the central atom and arranging them to minimize repulsion.

Question 23

How do multiple lone pairs influence the bond angles in a molecule, compared to just one lone pair

Answer 23

Multiple lone pairs cause even greater repulsion than a single lone pair, leading to significant reductions in bond angles as lone pairs push bonding pairs closer together

Question 24

Why is the bond angle in H₂O (104.5°) smaller than that in NH₃ (107°), despite both molecules having lone pairs?

Answer 24

Oxygen in H₂O has two lone pairs, which exert more repulsion on the bonding pairs compared to the one lone pair on nitrogen in NH₃.

Question 25

What role does VSEPR theory play in drug design?

Answer 25

VSEPR predicts 3D shapes of drug molecules, helping them interact effectively with enzymes and receptors.

Question 26

How does molecular shape affect drug action?

Answer 26

Molecular shape influences drug binding and ability to penetrate membranes, impacting effectiveness.

Question 27

How does VSEPR theory aid in enzyme-substrate interaction?

Answer 27

VSEPR predicts drug shapes, helping them fit precisely into enzyme active sites, boosting efficacy.

Question 28

What is the importance of VSEPR theory in designing drug delivery systems?

Answer 28

VSEPR helps design drug carriers like liposomes, optimizing their shape for efficient drug delivery.