chapter 3 assessment

give the meaning of the term electronegativity

give the meaning of the term electronegativity

the power of an atom to attract a pair of electrons in a covalent bond

how do permanent dipole-dipole forces arise between hydrogen chloride molecules

• the difference in electronegativity between chlorine and hydrogen ion

• so the hydrogen is slightly positive and the chloride ion is slightly positive

steps of how to figure out the shape of a molecule

• calculate the number of bonding electrons

• figure out how manny electrons are not bonded

• the lone pairs and number of elements bonded dictate the shape and weather is has a permanent dipole

suggest why bromine is different from magnesium and why magnesium is liquid of a greater temperature range

bromine is a simple molecule which has weak van der waal’s forces between the molecule. This gives it a lower melting/boiling point. magnesium is a gaint metallic molecule which with cations surrounded by a sea of delocalised electrons. this means that more energy is needed to overcome the strong electrostatic force of attraction between delocalised electrons and the ions. this means that the forces of attraction in magnesium in a liquid are stronger for a greater liquid range.

define and explain a dative covalent bond

a covalent bond (a shared pair of electrons) in which both electrons come from the same atom. so e.g both electrons come from a NH³ to aluminium chloride

how do bond angles change for dative covalent bonds

the bond angle decrease by 2.5 degrees per lone electron pairs

simple molecule

has a few atoms

macromolecular

billions of atoms bonded to each other

why silicon dioxide does not conduct electricity when moleten

there are no delocalised electrons which can move and carry charge

why type of crustal molecule does graphene have

macromolecular

why is graphene and excellent conductor od electricity

has delocalised electrons that can move through the crystal

what type of crystal is titanium

gaint metallic

why does titanium have a high melting point

strong electrostatic force of attraction between the atoms

why are metalls malleable

the layers of atoms slide over each other

why do objects with different strengths have simalar strengths

because both objects the same bond strength in metallic bonding