Chemical Bonds, Ionic, Covalent & Metallic

What is an ionic bond?

The electrostatic attraction between oppositely charged ions, formed when a metal transfers electrons to a non-metal.

What is a covalent bond?

A strong bond formed between two non-metal atoms when they share a pair of electrons.

What is a metallic bond?

The electrostatic attraction between positive metal ions and a 'sea' of delocalised electrons.

What type of bonding occurs when a metal reacts with a non-metal?

Ionic bonding.

What type of bonding occurs between non-metal elements?

Covalent bonding.

What is an ion?

An atom or group of atoms that has gained or lost electrons, resulting in an overall electric charge.

How do metal atoms form ions?

They lose electrons from their outer shell to form positively charged ions.

How do non-metal atoms form ions?

They gain electrons into their outer shell to form negatively charged ions.

What is the main goal for an atom when it forms a chemical bond?

To achieve a full outer shell of electrons, like a noble gas.

What is the structure of an ionic compound called?

A giant ionic lattice.

Describe the arrangement of ions in a giant ionic lattice.

A regular, repeating 3D pattern where each positive ion is surrounded by negative ions, and vice versa.

What type of force holds a giant ionic lattice together?

Strong electrostatic forces of attraction between oppositely charged ions.

Why do ionic compounds have high melting and boiling points?

A large amount of energy is required to overcome the many strong electrostatic forces of attraction between the ions in the lattice.

Why can ionic compounds conduct electricity when molten or dissolved in water?

The ions are free to move and carry an electrical charge.

Why can ionic compounds NOT conduct electricity when solid?

The ions are held in fixed positions within the lattice and are not free to move.

What does a dot and cross diagram show in ionic bonding?

The transfer of electrons from the metal atom to the non-metal atom.

In covalent bonding, the shared electrons are found in the _____ shells of the atoms.

outer

What is a molecule?

A group of two or more atoms held together by covalent bonds.

Substances made of small, simple molecules typically have _____ melting and boiling points.

low

What are the forces between molecules in a simple molecular substance called?

Intermolecular forces.

How does the strength of intermolecular forces compare to the strength of covalent bonds?

Intermolecular forces are much weaker than covalent bonds.

Why do simple molecular substances have low melting and boiling points?

Only a small amount of energy is needed to overcome the weak intermolecular forces between the molecules.

When a simple molecular substance melts or boils, which bonds are broken?

The weak intermolecular forces between molecules, not the strong covalent bonds within them.

Why do simple molecular substances not conduct electricity?

The molecules have no overall electric charge and there are no free electrons or ions to carry a current.

What happens to the strength of intermolecular forces as the size of a molecule increases?

The intermolecular forces increase in strength.

What is a polymer?

A very large molecule formed from many identical smaller molecules (monomers) joined together by covalent bonds.

Why are most polymers solid at room temperature?

The intermolecular forces between the large polymer chains are relatively strong, requiring more energy to overcome than in small molecules.

What is a giant covalent structure?

A structure where a very large number of atoms are all joined together by a network of strong covalent bonds.

Give two examples of giant covalent structures made of carbon.

Diamond and graphite.

Why do substances with giant covalent structures have very high melting points?

A very large amount of energy is needed to break the millions of strong covalent bonds throughout the structure.

In diamond, each carbon atom is covalently bonded to how many other carbon atoms?

Four.

Why is diamond extremely hard?

It has a rigid network structure held together by a vast number of strong covalent bonds.

Why does diamond not conduct electricity?

All of its outer electrons are used in covalent bonds, so there are no delocalised or free electrons to carry a charge.

In graphite, each carbon atom is covalently bonded to how many other carbon atoms?

Three.

Describe the structure of graphite.

It consists of layers of hexagonal rings of carbon atoms with no covalent bonds between the layers.

Why is graphite soft and slippery?

The layers of atoms can slide over each other because the forces between them are weak.

Why can graphite conduct electricity?

Each carbon atom has one delocalised electron that is free to move between the layers and carry a charge.

What is graphene?

A single layer of graphite, just one atom thick.

Describe the structure of a pure metal.

A giant structure of atoms arranged in a regular, repeating pattern.

In metallic bonding, the electrons from the outer shells of the metal atoms are ____, meaning they are free to move throughout the structure.

delocalised

Why are metals good conductors of electricity and heat?

Their delocalised electrons are free to move and carry electrical charge or transfer thermal energy through the structure.

Why do most metals have high melting and boiling points?

The metallic bonding is very strong, so large amounts of energy are needed to overcome the forces of attraction.

Why are pure metals often malleable (can be bent and shaped)?

The layers of atoms in the regular metallic structure can slide over one another.

What is an alloy?

A mixture of two or more elements, where at least one element is a metal.

How does the structure of an alloy differ from that of a pure metal?

An alloy contains atoms of different sizes, which distorts the regular layers of atoms found in a pure metal.

Why are alloys harder than pure metals?

The different-sized atoms disrupt the regular layers, making it more difficult for the layers to slide over each other.

What is represented by a single line in a stick diagram or structural formula?

A single covalent bond (a shared pair of electrons).

A double covalent bond consists of how many shared electrons?

Four electrons (two shared pairs).

A triple covalent bond consists of how many shared pairs of electrons?

Three shared pairs.

What is the name for the different structural forms of the same element in the same physical state, such as diamond and graphite?

Allotropes.

What are fullerenes?

Molecules of carbon atoms with hollow shapes, such as spheres or tubes.

What is the formula for Buckminsterfullerene, the first fullerene to be discovered?

C₆₀

What are carbon nanotubes?

Cylindrical fullerenes, which are like a layer of graphene rolled into a tube.

State a key property of carbon nanotubes that makes them useful for reinforcing materials.

They have a high tensile strength (are strong in tension).

A substance with a high melting point, which conducts electricity only when molten, is likely to have _____ bonding.

ionic

A substance that is a gas at room temperature and does not conduct electricity is likely to have a _____ _____ structure.

simple molecular

A very hard solid with a very high melting point that does not conduct electricity is likely to be a _____ _____ structure.

giant covalent

A shiny solid that can be bent into shape and conducts electricity is likely to have _____ bonding.

metallic

What is a limitation of a ball and stick model for representing an ionic lattice?

It incorrectly suggests there is a lot of free space between ions and the sticks imply directional bonds, whereas forces act in all directions.

What is a limitation of a dot and cross diagram for representing a molecule?

It does not show the 3D arrangement of the atoms in space.

What is the name for the strong forces of attraction that exist between oppositely charged ions?

Electrostatic forces.

In the reaction to form sodium chloride (NaCl), what happens to the electron from the sodium atom?

It is transferred to the outer shell of the chlorine atom.

After reacting, a sodium atom becomes a Na⁺ ion. What does a chlorine atom become?

A chloride ion (Cl^-).

When forming magnesium oxide (MgO), a magnesium atom loses two electrons. What happens to the oxygen atom?

It gains the two electrons from the magnesium atom.

The formula for magnesium chloride is MgCl₂. How many chlorine atoms are needed to bond with one magnesium atom?

Two.

What is the chemical formula for a water molecule?

H₂O

How many covalent bonds are there in a molecule of methane, CH₄?

Four.

What type of covalent bond exists in an oxygen molecule, O₂?

A double bond.

What type of covalent bond exists in a nitrogen molecule, N₂?

A triple bond.

Steel is an alloy primarily of which metal?

Iron.

What is the main compound found in sand, which is an example of a giant covalent structure?

Silicon dioxide (SiO₂).