bonding and structure

Define ionic bonding

The strong electrostatic force of attraction between the oppositely charged ions formed by the transfer of electrons

What is meant by isoelectric

Different atoms with the same number of electrons

How can electrolysis be used to show evidence for charged particles

• when a drop of green copper chromate is places on wet filter paper and electricity passes through it ions start to separate

• The positive copper ions move towards the cathode so will see a blue solution move

• The negative chromium ions will move towards the anode and see a yellow solution move

How is the Bond enthalpy the shorter the bond

Higher bond enthalpy with shorter bond length as the greater the electron density the stronger the attractive forces eg C=C has stronger bond enthalpy than C-C

Why is ice less dense than water

Ice forms a regular structure held by hydrogen bonding the molecules are further apart

Why are alcohols not as volatile as alkanes with similar masses

Due to hydrogen bonding alkanes have weaker London forces

Why can alcohols dissolve in polar solvents

As they can form hydrogen bonds with water molecules

How to test the charge of ions using copper ions and dichromate ions

The blue colour of the cu2+ ions migrate to the negative electrode and the yellow colour of the CrO42- ions migrate to the positive electrode

How can you see the charge of the ions using potassium manganate

A drop of potassium manganate, purple, is placed on moist filter paper on a microscope slide and the ends are connected to 24v power supply, after ten minutes, the MnO4- ions migrate has migrated to the positive electrode

What is a covalent bond

A strong bond caused by the electrostatic attraction between the bonding shared pair of electrons and the two nuclei

What is a dative covalent bond

When a shared pair of electrons in the covalent bond comes from only one of the bonding atoms

What is the difference between lone and bonding pairs

Lone pairs repel more than bonding pairs so reduces the bond angles by 2.5

What is the bond angle in a tetrahedral

109.5

What is the bond angle in a Trigonal pyramidal

107

What is the bond angle in bent

104.5

What are the bond angles in Trigonal bipyramidal

120 and 90

What is the bond angle in an octahedral

90

Define electronegativity

The relative tendency of an atom in a covalent bond in a molecule to attract a bonding pair of electrons in a covalent to itself

What affects electronegativity

Atomic radius across a period

Shielding down a group

When will a compound be ionic

When the difference in electronegativity is greater than 1.7

When does a polar covalent bond form

When it has a difference in electronegativity of 0.3-1.7

Where do London forces no occur

In ionic compounds

What affects the size of London forces

The number of electrons and the shape of the molecule

How does the shape of a molecule affect London forces

Long straight alkanes have a larger surface area of contact between molecules for London forces to form, compared to branched alkanes so have stronger London forces

How to test if liquid is polar or not

• a charged rod is brought close to a jet of liquid flowing from a burette

• If liquid is polar. The jet of liquid will be attracted to the electrostatic force of the rod

• The dipoles in the polar molecules will all align and the negative ends will be attracted to the positive ends, the stronger the dipole, the more deflection

What is the main factor affecting London forces

The amount of electrons and shape of the molecule

How does the shape of the molecule affect London forces

Long straight chains have a larger surface area of contact between the molecules for the London forcers to form, compared to spherical shaped branched alkanes so have stronger London forces

What is the bond angle of hydrogen bonding

180 degrees

What makes hydration of ions stronger

The higher the charge density, the greater the hydration enthalpy as the ions attract water molecules more strongly

What is and why the solubility of simple alcohols

The smaller the alcohols, the more soluble in water as they can form hydrogen bonds with water, the longer hydrocarbon chain the less soluble the alcohols.

What types of compounds are insoluble in water

Substances that cant form hydrogen bonds with water such as polar molecules like halogenoalkanes, or non polar like hexane

What will non polar solvents dissolve in and example

Non polar solvents eg iodine has only London forces will dissolve in hexane which also only contains London forces

What is a good solvent and why

Propanone as it has both polar and non polar characteristics, it can form London forces with some non polar solvents and its polar c=o bond can hydrogen bond with water

What affects metallic bonding

• nuclear strength / proton number

• Number of delocalised electrons

• Size of the ion