Topic 2 Bonding and Structure
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What are ions?
Charged particles that is formed when an atom loses or gains electrons
What is the charge of the ion when electrons are gained?
Negative
What are molecular ions?
Covalently bonded atoms that lose or gain electrons
Which electrons are lost when an atom becomes a positive ion?
Electrons in the highest energy levels
Do metals usually gain or lose electrons?
Lose electrons
Which are the 4 elements that don’t tend to form ions and why?
The elements are beryllium, boron, carbon and silicon Requires a lot of energy to transfer outer shell electrons
What are the 3 main types of chemical bonds?
● Ionic ● Covalent ● Metallic
Define ionic bonding
The electrostatic attraction between oppositely charged ions
What determines the strength of an ionic bond?
• Ionic radius and ionic charge • Ionic bonding is stronger and the melting points higher when the ions are smaller and/ or have higher charges.
How to draw dot and cross diagram for ionic bonding
Brackets with charges outside with the outershell displayed on the inside
Explain the trend in ionic radius down a group
Ionic radii increases going down the group. This is because down the group the ions have more shells of electrons and thus the outermost electron experience less pull from positive nucleus.
Explain the trend in ionic radius for this set of isoelectronic ions, N 3-, O 2-, F-, Ne, Na +, Mg 2+, Al 3+
There are increasing numbers of protons from N to F and then Na to Al but the same number of electrons. Therefore nuclear attraction between the outermost electrons and nucleus increases and ions get smaller
What are the physical properties of ionic compounds?
*high melting points *non conductor of electricity when solid *conductor of electricity when in solution or molten *brittle
In a solution of CuCrO 4 with connected electrodes which electrode will the 2 ions migrate to?
Cu 2+ - migrates to negative electrode CrO 4 2- - migrates to positive electrode
Define covalent bonding
Electrostatic attraction between a shared pair of electrons and the nuclei
Draw a dot and cross diagram for covalent molecules
Overlapping circles of outer shells
Define metallic bonding
Electrostatic attraction between the positive metal ions and the sea of delocalised electrons
Why does giant ionic lattices conduct electricity when liquid but not when solid?
In solid state the ions are in fixed positions and thus cannot move. When they are in liquid state the ions are mobile and thus can freely carry the charge
Giant ionic lattices have high or low melting and boiling point? Explain your answer
They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds
In what type of solvents do ionic lattices dissolve?
Polar solvents E.g water
Why are ionic compounds soluble in water?
Water has a polar bond. Hydrogen atoms have a δ+ charge and oxygen atoms have a δ- charge. These charges are able to attract charged ions
What is the effect of multiple covalent bonds on bond length and strength?
Double/triple bonds exert greater electron density therefore the attraction between nucleus and electron is greater resulting in a shorter and stronger bond.
What is a dative covalent bond?
A bond where both of the shared electrons are supplied by one atom
How are oxonium ions formed?
Formed when acid is added to water, H 3 O +