33 terms

iGCSE Chemistry: Structure and Bonding - test myself

STUDY
PLAY

Terms in this set (...)

Explain the term ionic bond
An ionic bond is the strong electrostatic attraction between oppositely charged ions
When are ions attracted to each other?
When the ions are oppositely charged
Describe the structure of an ionic compound, e.g NaCl.
A giant structure held together by the attraction between oppositely charged ions
Explain why magnesium oxide has a higher melting point than sodium chloride.
Mg²⁺ and O²⁻ ions have a higher charge than sodium and chloride therefore the electrostatic forces between the ions are much stronger. This requires more energy to break.
Explain, in terms of structure and bonding, why magnesium oxide has a higher melting point than sodium chloride
NaCl and MgO both have a giant ionic structure with strong electrostatic forces between oppositely charged ions. The Ions in MgO have a charge of 2 and -2, but in NaCl the charges are 1 and -1. So the bonds in MgO require more energy to break
Explain, in terms of structure and bonding, why sodium chloride has a very high melting point
NaCl has a giant ionic structure with strong electrostatic forces between oppositely charged ions that require a lot of energy to break
Why do ionic substance have high melting and boiling points?
The attraction between the oppositely charged ions is strong
Do ionic substances conduct electricity?
Not when solid, but they do when either molten or in solution
When can ionic substances conduct electricity?
When molten or dissolved
Describe the formation of a covalent bond
The sharing of a pair of electrons between two nuclei
Give the definition of a covalent bond
Strong electrostatic attraction between a shared pair of electrons and two nuclei
Explain why carbon dioxide gas, CO₂, is a gas at room temperature
Carbon dioxide has a simple molecular structure with weak intermolecular forces that require little energy to overcome
Explain why methane gas, CH₄, is a gas at room temperature
Methane has a simple molecular structure with weak intermolecular forces that require little energy to overcome
If a substance has a simple molecular structure, what physical state might it be at room temperature?
Gas or liquid (low melting point)
Explain why Silica, SiO₂ is a solid with a high melting point
Silica has a giant covalent structure with many strong covalent bonds that need a lot of energy to break
Suggest why buckminsterfullerene, C₆₀, has a low melting point.
Buckminsterfullerene has a simple molecular structure with weak intermolecular forces that require little energy to overcome
Explain, in terms of its structure, why graphite can act as a lubricant.
Graphite has weak forces of attraction between layers. These layers can slide over each other
Explain, in terms of its structure, why graphite can conduct electricity.
Graphite has delocalised electrons which can move
A substance is found not to conduct electricity even when molten. What type of bonding does the substance have?
Covalent
Explain what is meant by electric current
The rate of flow of charge particles (e.g. of electrons or ions)
Typically, so covalent substances conduct electricity?
No
(Triple only) Draw a diagram to show the bonding in a metal
(Triple only) Explain why metals are good conductors of electricity
Metals have delocalised electrons which are free to move
(Triple only) Explain why metals are malleable
Metals have layers of ions that can slide over each other
(Triple only) What does the word malleable mean?
able to be hammered or pressed into shape without breaking or cracking
(Triple only) Why do metals have high melting and boiling points?
There is a strong electrostatic attraction between a regular structure of positive metal ions and a sea of delocalised electrons
(Triple only) State whether covalent susbances conduct electricity, and explain why
There are no charged particles that are free to move
(Triple only) Why do covalent compounds (e.g H₂O) not conduct electricity?
There are no charged particles that are free to move
Do larger molecules have higher or lower boiling points than smaller molecules?
Higher
Why is the boiling point of a larger molecule higher than that of a smaller molecule?
Larger molecules have more attractions between them which must be overcome when a substance boils
Why is the melting point of a smaller molecule lower than that of a larger molecule?
Larger molecules have more attractions between them which must be overcome when a substance melts
(Triple only) Describe the bonding in a metal
The strong electrostatic attraction between a regular structure of positive metal ions and a sea of delocalised electrons
(Triple only) Describe the structure of metals
Metals have a giant regular structure of positive metal ions surrounded by a sea of delocalised electrons