JC1 H2 Chemistry: Chemical Bonding

Flashcards to help review key concepts related to chemical bonding, including covalent, ionic, and metallic bonds, as well as VSEPR theory, bond polarity, and hydrogen bonding.

What is a covalent bond?

A covalent bond is formed when atoms share valence electrons through overlap of orbitals.

How is an ionic bond defined?

An ionic bond is the electrostatic attraction between oppositely charged ions.

What is a metallic bond?

A metallic bond is the electrostatic attraction between a lattice of positive ions and delocalised electrons.

Describe the Valence Shell Electron Pair Repulsion (VSEPR) theory.

The VSEPR theory, principle 1: electron pairs around a centtral atom are located as far apart as possible to minmise electroni repulsion

principle 2 : lone pair-lone pair repulsion > lone pair-bond pair repulsion > bond pair-bond pair repulsion as lone pair of electrons take up more space around the central atom and repel other electrons more strongly

What is bond polarity?

Bond polarity occurs when bonding electrons are shared unequally between two atoms, leading to a partial positive and negative charge.

Explain what determines the strength of a covalent bond.

The strength of a covalent bond is determined by bond order, effectiveness of orbital overlap, and bond polarity.

Define hydrogen bonding.

Hydrogen bonding is the attraction between a hydrogen atom bonded to a highly electronegative atom (N, O, or F) and another electronegative atom.

What is the shape of a molecule with four bonding pairs and no lone pairs according to VSEPR theory?

Tetrahedral.

Describe the molecular geometry of a molecule with two bonding pairs and two lone pairs on the central atom according to VSEPR theory.

The molecular geometry is bent (or angular).

What is the bond angle in a trigonal planar molecular geometry?

120 degrees.

How does the presence of lone pairs affect the bond angles in a molecule?

Lone pairs take up more space than bonding pairs, which can distort bond angles, typically decreasing them.

For a molecule with five bonding pairs and no lone pairs, what is the VSEPR shape?

Trigonal bipyramidal.

What is the molecular shape of SF6 (sulfur hexafluoride) according to VSEPR theory?

Octahedral.

Describe the VSEPR shape of a molecule with one central atom, three bonding pairs, and one lone pair.

Trigonal pyramidal.

What factors influence the strength of hydrogen bonds in molecules?

The strength of hydrogen bonds is influenced by the electronegativity of the atom bonded to hydrogen (typically N, O, or F), the distance between the hydrogen atom and the electronegative atom, and the geometric arrangement of the molecule.

How do dipole-dipole interactions vary between polar molecules?

The strength of dipole-dipole interactions varies with the polarity of the molecules; more polar molecules exhibit stronger dipole-dipole attractions due to greater partial charges.

Explain how intermolecular forces affect the boiling point of a substance.

The stronger the intermolecular forces (hydrogen bonding > dipole-dipole > London dispersion), the higher the boiling point, as more energy is needed to overcome these forces.

Distinguish between London dispersion forces and dipole-dipole interactions.

London dispersion forces are temporary attractions due to the movement of electrons creating instantaneous dipoles, while dipole-dipole interactions occur between permanent dipoles of polar molecules.

What is the significance of polarizability in molecular interactions?

Polarizability is the tendency of an electron cloud to distort in response to an external electric field, affecting the strength of London dispersion forces; larger, more polarizable molecules have stronger intermolecular attractions.

How does the presence of functional groups influence intermolecular forces in organic compounds?

The presence of functional groups, such as hydroxyl (-OH) or carboxyl (-COOH), can significantly enhance intermolecular forces through hydrogen bonding and increase boiling and melting points compared to hydrocarbons

What are simple molecular structures, and how do they compare to giant molecular structures?

Simple molecular structures consist of small, discrete molecules held together by weak intermolecular forces (e.g., H2, O2, CH4). In contrast, giant molecular structures (or covalent networks) are composed of a vast number of atoms bonded together by covalent bonds in a continuous lattice (e.g., diamond, graphite, and silicon dioxide).

What distinguishes ionic structures from simple and giant molecular structures?

Ionic structures consist of a lattice of oppositely charged ions held together by strong electrostatic forces (ionic bonds). This differs from simple molecular structures, which have distinct, independent molecules, and from giant molecular structures, which are extensive networks of covalent bonds.

Describe the properties of simple molecular substances.

Simple molecular substances typically have low melting and boiling points, are often gases or liquids at room temperature, and do not conduct electricity due to the absence of free-moving charged particles.

What are the properties of giant molecular structures?

Giant molecular structures are characterized by high melting and boiling points due to the strong covalent bonds throughout the structure, are usually hard and brittle, and do not conduct electricity (except for graphite, which conducts due to delocalized electrons).

How do ionic compounds generally behave in terms of melting and boiling points?

Ionic compounds generally have high melting and boiling points due to the strength of the ionic bonds in the lattice structure, which require significant energy to break.

What is an example of a giant molecular structure and its key characteristic?

Diamond is an example of a giant molecular structure, characterized by its rigid lattice of carbon atoms bonded covalently in a tetrahedral arrangement, resulting in its hardness.

In what way do ionic compounds differ in solubility compared to simple molecular substances?

Ionic compounds are generally soluble in polar solvents like water due to the interaction between polar water molecules and ions, while simple molecular substances may vary in solubility depending on

What is ionic character in covalent compounds and how is it determined?

Ionic character in covalent compounds refers to the degree to which the bonding electrons are not shared equally, resulting in partial positive and negative charges. It is determined by the difference in electronegativity between the bonded atoms; greater differences lead to increased ionic character.

How does electronegativity difference influence ionic character?

The greater the electronegativity difference between the two atoms involved in a bond, the more ionic character the bond exhibits, as the more electronegative atom attracts the shared electrons more strongly.

What are the implications of ionic character in the properties of covalent compounds?

Covalent compounds with significant ionic character may exhibit properties similar to ionic compounds, such as higher boiling and melting points than expected and increased solubility in polar solvents.

What is covalent character in ionic compounds?

Covalent character in ionic compounds refers to the sharing of electron pairs between ions, which occurs when there is a significant overlap of atomic orbitals due to a small size and high charge of the cation involved.

How does the size and charge of ions affect covalent character in ionic compounds?

In ionic compounds, smaller cations and highly charged cations lead to increased covalent character due to their ability to polarize the electron cloud of the anion, resulting in