2.4 Electrons, Bonding and Structure for A-Level Chemistry (OCR)

What type of bonding involves electrostatic attraction between oppositely charged ions?

ionic bonding

Occurs when electrons are transferred from one atom to another.

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What structure is formed by oppositely charged ions arranged in a regular repeating pattern?

ionic lattice

The lattice extends in all directions in a giant structure.

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What type of ion is formed when an atom loses one or more electrons?

cation

Cations are positively charged ions.

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What type of ion is formed when an atom gains one or more electrons?

anion

Anions are negatively charged ions.

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True or False:

Ionic bonding involves the sharing of electrons between atoms.

False

Sharing occurs in covalent bonding.

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Which ion has the formula SO₄²⁻?

sulfate

A common polyatomic ion in many salts.

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Which ion has the formula OH⁻?

hydroxide

Found in alkalis such as sodium hydroxide.

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Which ion has the formula NO₃⁻?

nitrate

Common in fertilisers and nitric acid salts.

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Which ion has the formula CO₃²⁻?

carbonate

Found in compounds such as calcium carbonate.

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Which ion has the formula NH₄⁺?

ammonium

The only common positively charged compound ion.

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Fill in the blank:

Group 1 elements typically form ions with a charge of _______.

They lose one electron to form stable ions.

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Fill in the blank:

Group 7 elements typically form ions with a charge of _______.

−1

They gain one electron to achieve a full outer shell.

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What rule must be satisfied when writing the formula of an ionic compound?

total charge must equal zero

Positive and negative charges must balance.

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True or False:

The formula of magnesium oxide is MgO because Mg²⁺ and O²⁻ charges balance in a 1:1 ratio.

True

The simplest whole number ratio is used.

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What determines the ratio of ions in an ionic compound formula?

ionic charges

The ratio ensures overall electrical neutrality.

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What type of bond forms when two atoms share a pair of electrons?

covalent bond

Typically occurs between non-metal atoms.

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How is a single covalent bond usually represented in structural formulas?

line

Each line represents one shared pair of electrons.

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Fill in the blank:

A single covalent bond contains one _______ pair of electrons.

shared

Each atom contributes one electron to the pair.

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What is present between atoms in a double covalent bond?

two shared pairs of electrons

Represented by two lines between atoms.

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What is present between atoms in a triple covalent bond?

three shared pairs of electrons

Represented by three lines between atoms.

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True or False:

Covalent bonding involves the transfer of electrons between atoms.

False

Transfer occurs in ionic bonding.

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What type of bond forms when both electrons in the shared pair are donated by one atom?

dative covalent bond

Also known as a coordinate bond.

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Fill in the blank:

A dative covalent bond forms when one atom donates a _______ pair of electrons.

lone

The electron pair forms the shared bond.

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How is a co-ordinate bond represented in a diagram?

arrow

The arrow points from the donor atom to the acceptor atom.

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# True or False: Once formed, a **dative covalent bond** is indistinguishable from other covalent bonds.

True ## Footnote The bond behaves the same as a normal covalent bond.

Which **atom** in a **co-ordinate bond** must have a **lone pair** available for donation?

donor atom ## Footnote The acceptor atom must have an empty orbital.

What must the **acceptor atom** provide in order for a **co-ordinate bond to form**?

empty orbital ## Footnote The donated electron pair occupies this orbital.

What type of **bonding** involves attraction between **positive metal ions and delocalised electrons**?

metallic bonding ## Footnote Found in metals and alloys.

What **structure** are positive metal ions **arranged in within a metal**?

lattice ## Footnote A regular repeating arrangement of metal ions.

# True or False: In metallic bonding, electrons are **fixed between two atoms**.

False ## Footnote The electrons are delocalised and move freely.

What **term** describes electrons that are **not associated with a single atom** in a metal?

delocalised electrons ## Footnote They move throughout the metallic lattice.

What **attraction** holds the **metallic lattice** together?

electrostatic attraction ## Footnote Between positive metal ions and delocalised electrons.

# Fill in the blank: **Metals conduct electricity** because they contain mobile _\_\_\_\_\_\_ _\_\_\_\_\_\_.

delocalised electrons ## Footnote These electrons can carry charge through the structure.

What type of **ions** are present in a **metallic lattice**?

positive metal ions ## Footnote Formed when metal atoms lose outer electrons.

# True or False: Metallic bonding occurs between **metal atoms and non-metal atoms**.

False ## Footnote It occurs only between metal atoms.

What are the **four main types of crystal structure** found in solids?

1. Ionic 2. Metallic 3. Macromolecular/ Giant Covalent 4. Molecular ## Footnote These structures differ in bonding and intermolecular forces.

What type of **structure** consists of **oppositely charged ions** arranged in a **giant lattice**?

ionic lattice ## Footnote Strong electrostatic attractions exist between ions.

What type of **structure** consists of **positive ions** in a **lattice** surrounded by **delocalised electrons**?

metallic lattice ## Footnote This structure is responsible for metallic conductivity.

What type of **structure** forms a **giant network of atoms** joined by **covalent bonds**?

macromolecular/ Giant Covalent ## Footnote Also known as giant covalent structures.

What type of **structure** consists of **discrete molecules** held together by **intermolecular forces**?

molecular ## Footnote Intermolecular forces are weaker than covalent bonds.

Which **giant covalent structure** is formed by **carbon atoms** each bonded to four others in a **tetrahedral arrangement**?

diamond ## Footnote Very strong covalent bonds give diamond a very high melting point.

Which **form of carbon** has layers of atoms arranged in **hexagons** with **delocalised electrons between atoms**?

graphite ## Footnote Delocalised electrons allow graphite to conduct electricity.

# True or False: Diamond can conduct electricity because it has **delocalised electrons**.

False ## Footnote All electrons are involved in covalent bonds.

Which **solid** consists of molecules **held together by hydrogen bonding** in a lattice?

ice ## Footnote Hydrogen bonds exist between water molecules.

Which **molecular solid** forms a lattice of I₂ molecules **held together by intermolecular forces**?

iodine ## Footnote Weak intermolecular forces give iodine a relatively low melting point.

What type of **structure** does **magnesium** have in the solid state?

metallic ## Footnote Positive Mg²⁺ ions in a sea of delocalised electrons.

What type of **crystal lattice** does **sodium chloride** form?

ionic ## Footnote Na⁺ and Cl⁻ ions arranged in a giant ionic lattice.

# Fill in the blank: **Giant ionic lattices** have **high melting points** because of strong _\_\_\_\_\_\_ _\_\_\_\_\_\_ between ions.

electrostatic attractions ## Footnote Large amounts of energy are needed to overcome these forces.

Why can **graphite** conduct electricity but **diamond cannot**?

delocalised electrons in graphite ## Footnote Diamond has no free electrons to carry charge.

# Fill in the blank: During a **change of state**, energy is used to overcome _\_\_\_\_\_\_ _\_\_\_\_\_\_.

intermolecular forces ## Footnote Covalent bonds usually remain intact.

# True or False: Molecular substances generally have **lower melting points** than giant covalent structures.

True ## Footnote Intermolecular forces are weaker than covalent bonds.

What term describes a **pair of electrons involved in forming a covalent bond**?

bonding pair ## Footnote Shared between two atoms.

What term describes a **pair of outer-shell electrons not involved in bonding**?

lone pair ## Footnote Also called a non-bonding pair.

# Fill in the blank: Electron pairs arrange themselves as _\_\_\_\_\_\_ _\_\_\_\_\_\_ as possible around the **central atom**.

far apart ## Footnote This minimises repulsion between electron pairs.

Which type of **electron pair repulsion** is the **strongest**?

lone pair–lone pair repulsion ## Footnote Lone pairs occupy more space around the atom.

Which type of **electron pair repulsion** is the **weakest**?

bond pair–bond pair repulsion ## Footnote Bonding pairs are held between nuclei.

# True or False: **Lone pairs** repel **more strongly** than bonding pairs.

True ## Footnote This reduces bond angles in molecules.

What **shape** is formed when **two bonding pairs** surround a central atom with **no lone pairs**?

linear ## Footnote Bond angle is 180°.

What **shape** results from **three bonding pairs and no lone pairs** around the central atom?

trigonal planar ## Footnote Bond angle is 120°.

What **shape** results from **four bonding pairs and no lone pairs** around the central atom?

tetrahedral ## Footnote Bond angle is 109.5°.

What **shape** results when **three bonding pairs and one lone pair** surround a central atom?

trigonal pyramidal ## Footnote Bond angle is about 107°.

What **shape** results when **two bonding pairs and two lone pairs** surround a central atom?

non-linear ## Footnote Also called bent or V-shaped.

# Fill in the blank: **Lone pairs** reduce **bond angles** because they cause greater _\_\_\_\_\_\_ between electron pairs.

repulsion ## Footnote Lone pairs occupy more space than bonding pairs.

How many **electron pairs** can surround the **central atom** in molecules typically studied at this level?

up to six ## Footnote Includes both bonding and lone pairs.

# True or False: **Molecular shape** is determined only by **bonding pairs of electrons**.

False ## Footnote Lone pairs also affect the final shape.

What is the ability of an atom to **attract the bonding pair of electrons in a covalent bond** called?

electronegativity ## Footnote Values differ between elements and influence bond polarity.

What type of **bond** forms when two atoms with **different electronegativities** share electrons **unequally**?

polar covalent bond ## Footnote Electron density is pulled towards the more electronegative atom.

What **symbol** is used to show a **slight positive charge in a polar bond**?

δ⁺ ## Footnote Indicates lower electron density.

What **symbol** is used to show a **slight negative charge in a polar bond**?

δ⁻ ## Footnote Indicates higher electron density.

# True or False: A polar bond occurs when **electrons are shared equally between atoms**.

False ## Footnote Equal sharing produces a non-polar bond.

What term describes the **separation of charge** that occurs in a **polar molecule**?

permanent dipole ## Footnote One end of the molecule is slightly positive and the other slightly negative.

# Fill in the blank: A **molecule** has a **permanent dipole** when the centres of positive and negative _\_\_\_\_\_\_ do not coincide.

charge ## Footnote Caused by polar bonds and molecular shape.

Why might a molecule containing polar bonds have **no permanent dipole**?

dipoles cancel ## Footnote Symmetrical shapes cause bond dipoles to balance.

# True or False: **Carbon dioxide** has polar bonds but no permanent dipole.

True ## Footnote The linear shape causes bond dipoles to cancel.

What must be present in a **molecule** for a **permanent dipole** to form?

polar bonds and asymmetrical shape ## Footnote Both bond polarity and molecular geometry matter.

# Fill in the blank: Differences in _\_\_\_\_\_\_ between atoms cause **polar covalent bonds**.

electronegativity ## Footnote The greater the difference, the more polar the bond.

What are the **weak forces of attraction** that occur **between molecules** called?

intermolecular forces ## Footnote These forces influence physical properties such as boiling point.

What type of **intermolecular force** occurs between **molecules with permanent dipoles**?

permanent dipole–dipole forces ## Footnote Occurs when molecules contain polar bonds and an overall dipole.

What type of **intermolecular force** arises from **temporary fluctuations in electron distribution**?

induced dipole–dipole forces ## Footnote Also called London or dispersion forces.

# Fill in the blank: **Induced dipole–dipole forces** are also known as _\_\_\_\_\_\_ _\_\_\_\_\_\_ forces.

London dispersion ## Footnote Often collectively called van der Waals forces.

What type of **intermolecular force** occurs when **hydrogen is bonded to nitrogen, oxygen or fluorine**?

hydrogen bonding ## Footnote This is the strongest common intermolecular force.

# True or False: **Hydrogen bonding** is a type of **covalent bond**.

False ## Footnote It is an intermolecular force, not a covalent bond.

Why are **hydrogen bonds** particularly **strong** compared with other intermolecular forces?

large electronegativity difference ## Footnote This creates a highly polar H–X bond.

How do stronger intermolecular forces affect **boiling points**?

increase boiling point ## Footnote More energy is required to separate molecules.

# True or False: Substances with only **London forces** usually have **lower boiling points** than those with hydrogen bonding.

True ## Footnote London forces are the weakest intermolecular forces.

Why does **ice** have a **lower density than liquid water**?

Hydrogen bonding forms an open lattice. ## Footnote The structure holds molecules further apart.

Why does **water** have an **unusually high boiling point** compared with similar molecules?

hydrogen bonding ## Footnote Extra energy is required to break these interactions.

# Fill in the blank: **Intermolecular forces** are _\_\_\_\_\_\_ than covalent bonds.

weaker ## Footnote Therefore molecular substances usually have lower melting points.

What **property of molecules** mainly determines the **strength of induced dipole–dipole forces**?

number of electrons ## Footnote Larger electron clouds are more easily distorted.

# True or False: All molecules experience **induced dipole–dipole forces**.

True ## Footnote These forces occur even in non-polar molecules.

2.4 Electrons, Bonding and Structure Flashcards

Relate bonding and structure to physical and chemical properties by analysing electron interactions and molecular geometry. (90 cards)