IGCSE CHEM_CHAP 2.5_Simple molecules and covalent bonds.

Covalent bond

A bond formed when a pair of electrons is shared between two atoms, usually non-metals; Liên kết cộng hóa trị.

Molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound; Phân tử.

Single covalent bond

A bond where one pair of electrons is shared between two atoms; Liên kết cộng hóa trị đơn.

Double covalent bond

A bond where two pairs of electrons are shared between two atoms; Liên kết cộng hóa trị đôi.

Triple covalent bond

A bond where three pairs of electrons are shared between two atoms; Liên kết cộng hóa trị ba.

Intermolecular forces

Weak forces of attraction between different molecules; Lực liên phân tử.

Intramolecular forces

Strong forces (like covalent bonds) that hold atoms together within a single molecule; Lực nội phân tử.

Noble gas configuration

A stable electron arrangement with a full outer shell; Cấu hình khí hiếm.

Covalent bond

A bond formed when a pair of electrons is shared between two atoms, usually non-metals; Liên kết cộng hóa trị.

Molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound; Phân tử.

Single covalent bond

A bond where one pair of electrons is shared between two atoms; Liên kết cộng hóa trị đơn.

Double covalent bond

A bond where two pairs of electrons are shared between two atoms; Liên kết cộng hóa trị đôi.

Triple covalent bond

A bond where three pairs of electrons are shared between two atoms; Liên kết cộng hóa trị ba.

Intermolecular forces

Weak forces of attraction between different molecules; Lực liên phân tử.

Intramolecular forces

Strong forces (like covalent bonds) that hold atoms together within a single molecule; Lực nội phân tử.

Noble gas configuration

A stable electron arrangement with a full outer shell; Cấu hình khí hiếm.

50 Short-Answer Questions

Shared pair of electrons

What is formed when two atoms create a covalent bond?

Two non-metals

Between what types of elements do covalent bonds typically form?

Noble gas configuration

What type of electronic configuration do atoms achieve by sharing electrons?

Overlapping outer shells

How is a covalent bond shown in a dot-and-cross diagram?

Covalent bond

What is the bond in a hydrogen (H2) molecule?

1

How many pairs of electrons are shared in a single covalent bond?

2

How many pairs of electrons are shared in a double covalent bond?

3

How many pairs of electrons are shared in a triple covalent bond?

H2, Cl2, H2O, CH4, NH3, HCl

What are examples of molecules with single covalent bonds?

CO2

Which molecule mentioned in the notes contains double covalent bonds?

N2

Which molecule mentioned in the notes contains a triple covalent bond?

4

How many covalent bonds does carbon form in a methane (CH4) molecule?

3

How many covalent bonds does nitrogen form in an ammonia (NH3) molecule?

2

How many covalent bonds does oxygen form in a water (H2O) molecule?

1

How many covalent bonds does hydrogen form in any molecule?

Methane

What is the name of the molecule with the formula CH4?

Ammonia

What is the name of the molecule with the formula NH3?

Hydrogen chloride

What is the name of the molecule with the formula HCl?

Intramolecular forces

What is another name for the strong covalent bonds within a molecule?

Intermolecular forces

What are the forces called that exist between different molecules?

Low

Do simple molecular compounds have high or low melting points?

Low

Do simple molecular compounds have high or low boiling points?

Intermolecular forces are weak

Why do simple molecular compounds have low melting points?

Little energy

How much energy is needed to overcome weak intermolecular forces?

Strong

How strong are the covalent bonds within a molecule compared to intermolecular forces?

Poor (Cannot conduct)

How is the electrical conductivity of simple molecular compounds?

There are no ions or free electrons

Why can simple molecular compounds not conduct electricity?

No charge

Do simple molecules carry an overall electrical charge?

2

How many electrons does a hydrogen atom need in its outer shell to be stable?

8

How many electrons do most non-metals (except H) need in their outer shell to be stable?

Dots and crosses

What symbols are used in diagrams to distinguish electrons from different atoms?

Overlap

What must happen to the circles representing shells in a covalent diagram?

They increase

What happens to melting points as the size of simple molecules increases?

Gases or liquids

What physical states are most simple molecular compounds at room temperature?

Double covalent bond

What type of bond exists between C and O in CO2?

Triple covalent bond

What type of bond exists between two nitrogen atoms in N2?

6

How many total electrons are shared in a triple covalent bond?

4

How many total electrons are shared in a double covalent bond?

2

How many total electrons are shared in a single covalent bond?

Strong covalent bonds

Which bonds are NOT broken when a simple molecular liquid boils?

Weak intermolecular forces

Which bonds are broken when a simple molecular liquid boils?

Carbon dioxide

What is the name for the molecule CO2?

Nitrogen gas

What is the name for the molecule N2?

Non-metal and non-metal

Covalent bonding occurs between which two categories of elements?

It remains neutral

What is the overall charge of a covalent molecule?

Outer shell

Which electron shell is involved in forming covalent bonds?

Water

Which molecule has two single covalent bonds and two lone pairs on the central atom?

Covalent

Which is generally stronger: a covalent bond or an intermolecular force?

Electron sharing

What is the fundamental mechanism of covalent bonding?

Full outer shell

What does sharing electrons allow atoms to achieve?