IB Chemistry SL Topic 4: Bonding and Structure

exothermic

more energy is given out than needs to be put in

endothermic

more energy is required to break the reactant bonds than is given out when the products are formed

intramolecular forces

the forces of attraction between atoms within a molecule

intermolecular forces

the forces of attraction between particles of a compound

ionic bonding (how it works)

One atom will donate a certain number of valence electrons to another element, the donor now becoming a negative ion and the recipient becoming a positive ion. They donate and receive enough electrons to both fill their valence shell

electron affinity definition

the amount of energy given out when an atom of an element gains an electron

lattice enthalpy

the amount of energy released when a lattice is formed

what types of elements form ionic bonds?

metals on the left of the periodic table who can lose electrons and non-metals on the right of the periodic table who want to gain electrons.

Also transition metals

ionic bonding defintion

electronic attraction between oppositely charged ions

polyatomic ions

the positive and negative ions formed when more than one element is joined together. In polyatomic ions the charge is spread over the whole ion not localized on one atom

How to predict what type of bond elements will form

If the difference in electronegativity is high then they will form an ionic bond (generally needs to be more than 1.8 difference)

Covalent bonding (how it works)

Two atoms share an electron or electrons to make it so they both have full valence shells.

single covalent bond

when one pair of electrons is shared between two atoms

Lewis structure

diagram that shows all the pairs of outer electrons in a molecule

lone pair of electrons

pair of electrons that remain un-bonded in a covalently bonded molecule

double covalent bond

when two pairs of electrons are shared between two atoms

triple covalent bonds

when three pairs of electrons are shared between two atoms

dative or coordinate covalent bond

when both of the electrons in a shared electron pair originate from one atom

strength and length of covalent bonds

the bigger the bond (single, double or triple) then the shorter the bond but also the stronger

explain the polarity of covalently bonded molecules

if the both atoms in the molecule are the same element then the bond is non-polar, if the elements are different then the atom that is larger will attract the electrons more and thus the charge will be uneven, creating a polar molecule

what is a dipole moment

when a polar molecule is put between two electrically charged plates, with the negative end of the molecule will be attracted to the positive plate and visa versa

VSEPR theory

valence shell electron pair repulsion theory states that the repulsion between pars of electrons around the central atom causes the other atoms to be arranged so that they are as far away from each other as possible

van der Waals' forces

the forces exhibited in all particles

Dipole-dipole forces

when the negative pole of one polar molecule is attracted to the positive pole of another polar molecule

dipole

when the bond polarities don't equal zero

hydrogen bonding

when a hydrogen is covalently bonded to fluorine, oxygen or nitrogen

metallic bonding

when metal atoms are together one or more of their valence electrons become delocalized and move throughout the metal structure

physical properties of van der Waals'

low melting and boiling point, insoluble in water, soluble in non polar solvents, non conductor

physical properties of dipole:dipole

higher melting and boiling than van der Waals', miscible with water and non-polar solvents, non conductor

physical properties of hydrogen bonding

higher melting and boiling point than dipole dipole, miscible with water, non condoctor

physical properties of ionic bonding

high melting and boiling, soluble n water, non conductor as solid but conductor as aqueous

physical properties of metallic bonding

high melting and boiling, insoluble in water and non polar solvents, good conductor

physical properties of giant covalent

high melting and boiling, insoluble in water and non polar solvents, non conductor

allotropy

being able to exist in more than one physical form or allotrope

diamond

carbon atom bonded to four other carbons to form tetrahedral structure

graphite

carbon atom bonded to three other carbon atoms to form hexagonal rings, layers of rings attached by delocalized electrons

fullurene

carbon atoms form hexagonal and pentagonal rings to form a sphere