Simple Molecules & Covalent Bonds (Cambridge (CIE) IGCSE Chemistry)
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What is represented by a short straight line between two atoms?
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What is represented by a short straight line between two atoms?
A short straight line between two atoms represents a covalent bond.
What is a covalent bond?
A covalent bond is a type of chemical bond where atoms share pairs of electrons with each other.
True or False?
Covalent bonds involve the transfer of electrons.
False.
Covalent bonds involve sharing electrons, not transferring them.
What type of materials form a covalent bond?
The materials that form covalent bonds are non-metals.
What makes each atom more stable in a covalent bond?
Sharing electrons in the covalent bond allows each atom to achieve an electron configuration similar to a noble gas.
What is formed when a group of two or more atoms covalently bond together?
A compound / molecule is formed when a group of two or more atoms covalently bond together.
What is the smallest molecule?
The smallest molecule is hydrogen, H2.
What do dots and crosses represent in a dot and cross diagram?
In a dot and cross diagram, dots and crosses represents electrons.
Draw the dot and cross diagram for hydrogen, H2.
The dot and cross diagram for hydrogen, H2, is:
Draw the dot and cross diagram for hydrogen chloride, HCl.
The dot and cross diagram for hydrogen chloride, HCl, is:
Draw the dot and cross diagram for water, H2O.
The dot and cross diagram for water, H2O, is:
True or False?
The dot and cross diagram for oxygen is:
(Extended Tier Only)
False.
The correct dot and cross diagram for oxygen is:
Draw the dot and cross diagram for carbon dioxide, CO2. (Extended Tier Only)
The dot and cross diagram for carbon dioxide, CO2, is:
True or False?
If two adjacent atoms share two pairs of electrons, two covalent bonds are formed, also known as a triple bond. (Extended Tier Only)
False?
If two adjacent atoms share two pairs of electrons, two covalent bonds are formed, also known as a double bond.
What type of bond is formed if three pairs of electrons are shared between two atoms? (Extended Tier Only)
A triple bond is formed if three pairs of electrons are shared between two atoms.
What type of covalent bond exists between the two carbon atoms in ethene, C2H4? (Extended Tier Only)
A double bond exists between the carbon atoms in ethene.
What is the completed dot-and-cross diagram for methanol?
(Extended Tier Only)
The completed dot-and-cross diagram for methanol is:
True or False?
Simple molecular structures have high melting and boiling points.
False.
Simple molecular structures have low melting and boiling points.
What is the difference between covalent bonds and intermolecular forces?
Covalent bonds are strong bonds that hold atoms together within a molecule, while intermolecular forces are weak attractive forces that exist between different molecules.
True or False?
Covalent compounds are good conductors of electricity.
False.
Covalent compounds are poor conductors of electricity.
What are simple molecular structures?
Simple molecular structures are small molecules with covalent bonds, which have weak forces between the molecules (intermolecular forces).
Why are covalent compounds generally poor conductors of electricity? (Extended Tier Only)
Covalent compounds are generally poor conductors of electricity because they do not contain free ions or electrons to carry the current.
True or False?
Covalent bonds break when a covalent substance melts or boils.
False.
Intermolecular forces break when a covalent substance melts or boils..
What happens to melting and boiling points as the relative molecular mass of a substance increases? (Extended Tier Only)
As the relative molecular mass of a substance increases, the melting and boiling points also increase due to the increased number of electrons and stronger intermolecular forces.
What are insulators?
Insulators are materials that do not allow the flow of electric charge or heat, and common insulators include plastics, rubber, and wood.
Why do simple molecular structures have low melting and boiling points? (Extended Tier Only)
Simple molecular structures have low melting and boiling points due to weak intermolecular forces which require small amounts of energy to overcome.
True or False?
Simple molecular structures are often gases or liquids at room temperature.
True.
Simple molecular structures are often gases or liquids at room temperature.
