IGCSE CHEM_CHAP 2.6_Giant covalent structures.

Giant covalent structure

A three-dimensional network of atoms held together by many strong covalent bonds; Cấu trúc khổng lồ liên kết cộng hóa trị.

Diamond

An allotrope of carbon where each atom is covalently bonded to 4 other carbon atoms in a tetrahedral shape; Kim cương.

Graphite

An allotrope of carbon where each atom is covalently bonded to 3 other carbon atoms in layers of hexagonal rings; Than chì.

Delocalised electrons

Electrons that are not associated with a single atom or bond and are free to move and carry charge; Electron tự do (electron không tập trung).

Silicon(IV) oxide

Also known as silica, a giant covalent structure where each silicon atom is bonded to 4 oxygen atoms; Silicon dioxide.

Tetrahedral

A 3D shape where a central atom is bonded to four others, forming a pyramid-like structure; Hình tứ diện.

Lubricant

A substance used to reduce friction, a common use for graphite due to its sliding layers; Chất bôi trơn.

Diamond and graphite

What are the two main allotropes of carbon mentioned with giant covalent structures?

4

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

Tetrahedral

What is the 3D shape of the structure in diamond?

Strong covalent bonds

Why is diamond extremely hard?

Poor (Cannot conduct)

How is the electrical conductivity of diamond?

There are no delocalised electrons

Why can diamond not conduct electricity?

Cutting tools

What is a common industrial use for diamond due to its hardness?

3

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

Hexagonal rings

What shape are the rings that make up the layers in graphite?

Weak intermolecular forces

What holds the layers of graphite together?

Soft and slippery

What physical property does graphite have because its layers can slide?

Delocalised electron

What does each carbon atom in graphite have that allows it to conduct electricity?

Good

How is the electrical conductivity of graphite?

Lubricant

What is a common use for graphite because its layers slide over each other?

Electrodes

What is a common use for graphite in batteries due to its conductivity?

Silicon(IV) oxide

What is the scientific name for silica or sand?

SiO2

What is the chemical formula for silicon(IV) oxide?

4

In silicon dioxide, how many oxygen atoms is each silicon atom bonded to?

2

In silicon dioxide, how many silicon atoms is each oxygen atom bonded to?

High

Do giant covalent structures have high or low melting points?

High

Do giant covalent structures have high or low boiling points?

Many strong covalent bonds

Why do giant covalent structures require a lot of energy to melt?

Rigid

How would you describe the overall structure of diamond and silicon dioxide?

Sand

What is the most common natural form of silicon(IV) oxide?

Diamond and Silicon(IV) oxide

Which two giant structures have a similar tetrahedral arrangement?

Layers

What is the structural arrangement of graphite?

Heat

Besides electricity, what else can graphite conduct well?

Giant lattice

What is another term for a giant covalent structure?

Non-metals

What type of elements are typically found in giant covalent structures?

Carbon

What element makes up both diamond and graphite?

Intramolecular forces

What are the strong bonds within the giant lattice called?

Silicon and Oxygen

Which two elements make up silica?

Si2O4

What is the unsimplified formula for the repeating unit in silicon dioxide?

Sliding layers

Why is graphite used in pencils?

It remains solid

What happens to diamond at very high temperatures compared to simple molecules?

They carry charge

What do delocalised electrons do to allow conduction?

No

Does silicon dioxide conduct electricity?

1

How many delocalised electrons are there per carbon atom in graphite?

Both have strong covalent bonds

Why are both diamond and silica very hard?

Transparent

What is a visual property of pure diamond?

Dull and black

What is a visual property of graphite?

Energy

What is needed in large amounts to break the bonds in these structures?

3D network

What type of network do covalent bonds form in diamond?

2D layers

What type of network do covalent bonds form in graphite?

Insoluble

Are giant covalent structures usually soluble or insoluble in water?

Covalent

What type of bonding is present in silicon(IV) oxide?

Allotropes

What is the term for different forms of the same element in the same state?

Carbon atoms

What are the spheres in a graphite diagram usually representing?

Melting point

Which property is high for all three structures: diamond, graphite, and silica?

Diamond

Between diamond and graphite, which is a better abrasive for cutting?