Types of Bonding & Properties (AQA A Level Chemistry): Flashcards

Ions achieve the electronic configuration of a noble gas (full outer shell). This is stable because a full outer shell minimises the energy of the ion.

An Ionic lattice is a regular, repeating crystalline arrangement of oppositely charged ions held together by electrostatic forces acting in all directions. Positive and negative charges alternate so the overall structure is electrically neutral.

A chloride ion (Cl^-) also has the same electronic configuration as argon: [2,8,8]^-.

A potassium ion (K⁺) has the same electronic configuration as argon: [2,8,8]⁺.

Ionic compounds contain strong electrostatic forces of attraction between oppositely charged ions. A large amount of energy is required to overcome these forces and separate the ions.

A Covalent bond is the electrostatic attraction between the positively charged nuclei of two non-metal atoms and a shared pair of electrons in their outer shells.

False.

Covalent bonding occurs between non-metal atoms. Metal atoms transfer electrons to non-metals in ionic bonding rather than sharing them.

An expanded octet occurs when the central atom has more than eight electrons in its outer shell. It is only possible for Period 3 elements and beyond, such as sulfur and phosphorus.

In a dot-and-cross diagram, dots represent electrons from one atom and crosses represent electrons from the other atom. Shared electrons are shown as pairs in the overlap between the atoms.

An Electron-deficient is a term describing a molecule where its central atom has fewer than eight electrons in its outer shell. Examples include BeCl₂ and BF₃, which are stable despite the incomplete outer shell.

Nitrogen forms a triple bond in N₂, sharing 6 electrons (3 pairs). Each nitrogen atom contributes 3 electrons to the bond, giving both atoms a full outer shell of 8 electrons.

Dative covalent bonding is a type of covalent bond in which both electrons in the shared pair come from the same atom. The atom donating the lone pair is the donor; the atom accepting it is electron-deficient.

False.

In a dative covalent bond, both electrons come from the same atom (the donor). The other atom is electron-deficient and has an unfilled outer orbital to accept the pair.

The ammonium ion (NH₄⁺) forms when NH₃ donates its lone pair to H⁺. The H⁺ ion is electron-deficient and has space for two electrons in its outer shell.

A dative covalent bond is drawn as an arrow pointing from the donor atom (lone pair) to the electron-deficient acceptor atom. An ordinary covalent bond is shown as a line or a pair of dots/crosses.

A Ligand is a molecule or ion that donates a lone pair of electrons to a transition metal ion, forming a dative covalent (coordinate) bond.

Aluminium chloride exists as a monomer (AlCl₃) at high temperatures. At lower temperatures, two molecules join to form a dimer (Al₂Cl₆) via dative covalent bonds from chlorine lone pairs to aluminium atoms.

Oxygen forms a dative covalent (coordinate) bond with Fe(II) in haemoglobin. Carbon monoxide (CO) can displace oxygen because it also donates a lone pair to Fe(II) and binds more strongly.

A Dot-and-cross diagram is a diagram showing the arrangement of outer-shell electrons in ionic or covalent compounds. Dots represent electrons from one atom and crosses represent electrons from the other, with shared pairs shown in overlapping regions.

In a dot-and-cross diagram for an ionic compound, the charge on each ion is written at the top right-hand corner. Brackets are used to show that the charge is spread evenly across the ion.

False.

Dot-and-cross diagrams show only the outer-shell (valence) electrons of each atom involved.

Lithium nitride contains Li⁺ (Group 1, loses 1 electron) and N^3- (Group 5, gains 3 electrons). Three lithium atoms are needed per nitrogen atom to balance the charges.

In a covalent dot-and-cross diagram, atoms share their outer valence electrons to achieve a full outer shell, similar to the configuration of a noble gas.

In an ionic diagram, electrons are fully transferred and each ion is drawn separately with brackets and a charge. In a covalent diagram, electrons are shared and shown as pairs in the overlap between two atoms.

Brackets enclose each ion to show that the charge indicated at the top right is distributed evenly across the entire ion, not localised on any one part of it.

Metallic bonding is the strong electrostatic attraction between a lattice of positively charged metal ions and a 'sea' of delocalised electrons that surrounds them and is free to move throughout the structure.

False.

Delocalised electrons are not bound to any specific atom. They are free to move throughout the entire metallic lattice, forming the 'sea' of electrons that holds the structure together.

When metal atoms form a lattice, their outer-shell electrons become delocalised. The metal atoms then become positively charged ions. The strong forces between these positive centres and the 'sea' of electrons constitute the metallic bond.

The positive metal ions repel each other electrostatically, keeping them evenly spaced. The sea of delocalised electrons between them also helps maintain the regular lattice arrangement.

In a metallic lattice, metal ions are packed in hexagonal layers or in a cubic arrangement. The delocalised electrons allow the metal to conduct electricity and heat.

Delocalised electrons are electrons that are not associated with any one particular atom. They come from the outer shells of metal atoms and are free to move throughout the entire metallic lattice, forming a 'sea' that holds positive metal ions together.

Increasing the number of delocalised electrons per atom strengthens metallic bonding, as there are more mobile charges contributing to the electrostatic attraction with the positive metal ions.

A Giant ionic lattice is a regular, repeating three-dimensional arrangement of alternating positive and negative ions held together by strong electrostatic forces acting in all directions. Examples include NaCl and MgO, which have cubic lattices.

In a giant ionic lattice, positive and negative ions are arranged in an alternating fashion. The type of lattice formed depends on the sizes of the positive and negative ions.

True.

Both MgO and NaCl form cubic ionic lattices, though the exact arrangement and lattice energy differ due to differences in ionic charge and size.

Ionic compounds are crystalline because their ions are arranged in a regular and repeating pattern, forming an ordered lattice structure. This gives them well-defined shapes and flat faces.

In an ionic lattice, the attraction between ions acts in all directions. Each ion is attracted to all oppositely charged ions around it, making the overall lattice electrically neutral.

Giant ionic lattices give ionic compounds high melting and boiling points (strong electrostatic forces require large energy to overcome), brittleness (ion layers can slip to align like charges), and the ability to conduct electricity when molten or dissolved (ions are free to move).

A Non-directional bonding is where the electrostatic attraction between oppositely charged ions acts equally in all directions, so there is no preferred orientation for the ionic bond. Each ion attracts all surrounding oppositely charged ions equally.

A Simple molecular lattice is a lattice in which discrete covalent molecules are held together by weak intermolecular forces (such as van der Waals forces). Examples include iodine, buckminsterfullerene (C₆₀) and ice.

False.

Diamond and graphite are giant molecular (covalent) lattices, in which all atoms are connected by strong covalent bonds throughout the structure. Simple molecular lattices contain discrete molecules.

Covalent compounds can form simple molecular lattices (e.g. iodine, ice) or giant molecular lattices (e.g. diamond, graphite, silicon(IV) oxide). Graphite, diamond and buckminsterfullerene are all allotropes of carbon.

Simple molecular substances have weak intermolecular forces between discrete molecules. Little energy is needed to overcome these forces, giving low melting and boiling points. The strong covalent bonds within molecules are not broken during melting.

A Giant molecular lattice is a lattice in which all atoms are covalently bonded together in a continuous three-dimensional network. Examples include diamond, graphite and silicon(IV) oxide. These structures have very high melting points.

Buckminsterfullerene has the formula C₆₀. It is an example of a simple molecular lattice. It is an allotrope of carbon.

In giant molecular structures, every atom is bonded to its neighbours by strong covalent bonds throughout the entire lattice. Enormous amounts of energy are required to break these bonds and separate the atoms.

A Giant metallic lattice is a structure in which positive metal ions are arranged in regular layers (hexagonal or cubic) and surrounded by a sea of delocalised electrons. The strong electrostatic attraction between the ions and electrons gives metals their characteristic properties.

The strength of metallic bonding increases when the number of delocalised electrons per atom increases, when the positive charge on metal centres increases, and when the size of the metal ions decreases.

False.

Metals conduct electricity in both the solid and liquid states because delocalised electrons are free to move in both states.

When a force is applied, layers of metal ions can slide over one another. The metallic bonds re-form in the new position because the attraction between ions and delocalised electrons acts in all directions, so the lattice is not broken.

Across Period 3, the number of outer electrons increases: Na has 1, Mg has 2, Al has 3. As a result, electrical conductivity increases across the period.

An Alloy is a mixture of a metal with one or more other elements (metals or non-metals). An alloy is formed when atoms of another element are introduced into the metallic lattice, distorting the regular structure.\n\nThis distortion makes it harder for layers to slide, so alloys are generally harder and stronger than pure metals.

Heat is conducted through a metal by delocalised electrons: they absorb kinetic energy from vibrating metal ions and carry it rapidly throughout the lattice, transferring energy from hot regions to cooler regions.

A giant ionic lattice is a three-dimensional arrangement of oppositely charged ions held together by strong electrostatic forces acting in all directions.

False.

In the solid state, ions are in fixed positions and cannot move. Ionic compounds only conduct electricity when molten or in aqueous solution, where ions are free to move.

Metals are malleable because when a force is applied the metal layers can slide, and the metallic bonds re-form, so the lattice is not broken.

Mg²⁺ and O^2- ions have a higher charge density than Na⁺ and Cl^- ions, so the electrostatic attraction between them is greater, requiring more energy to overcome.

A giant covalent lattice is a three-dimensional network of atoms joined by a very large number of covalent bonds throughout the whole structure, giving very high melting and boiling points.

Simple covalent compounds have low melting and boiling points because only weak intermolecular forces need to be overcome, not the covalent bonds themselves.

False.

Graphite conducts electricity because it has delocalised electrons between the carbon layers that are free to move when a voltage is applied. Diamond does not conduct because all four outer electrons are used in covalent bonds.