1.3 - Bonding

Define covalent bond

electrostatic attraction between shared pair of e- and nuclei of bonded e-

Define lone pair

pair of unshared e- in outer shell of atom

Define co-ordinate bond

shared pair of e- between two atoms where one atom provides both e-

Define octet rule

when reacting, atom tends to gain, lose or share electrons to achieve 8 in outer shell

Define electronegativity

extent an atom attracts bonding e- in covalent bond

Define polar bond

covalent bond with unequal sharing of bonding e-

Define delocalised electrons

outer e- don’t have fixed positions but move freely

Define metallic bond

electrostatic attraction between +ve metal ions and delocalised e-

Define ionic bond

electrostatic attraction between oppositely charged ions formed by e- transfer

What are noble gases described as?

monatomic as stable and full outer shell so don’t form bonds

Monatomic

exists as one atom

3 types of bonding with electrostatic attraction between oppositely charged particles

metallic, ionic and covalent

What is metallic bonding between?

+ve metal ions in metal element/alloy and delocalised e-

What increases strength of metallic bonding?

more delocalised e-

What is ionic bonding between?

metal and non-metal ions in ionic compounds

What increases strength of ionic bond?

higher charge

What is covalent bonding between?

shared pair of e- and nuclei of bonded e-

Exceptions to octet rule

expanded/contracted octet

What becomes bonding pair in co-ordinate bonding?

lone pair becomes bonding pair

What is co-ordinate bond drawn as?

arrow

What exists as a dimer - example

aluminium chloride

What is a dimer?

two molecules joined together

Electronegativity in one element molecules

e- pairs in bond equally shared between two atoms and atoms exert equal attractive forces upon e- pair so no difference in EN

What scale is electronegativity represented on?

Pauling scale

How does electronegativity change across periodic table?

decreases down group, increases across period

Why does electronegativity increase across period?

increased nuclear charge, decreased atomic radius, similar shielding

Why does electronegativity decrease down a group?

increasing nuclear charge, increasing atomic radius, increasing shielding

Most electronegative element

fluorine

Least electronegative element

francium

What affects polarity?

bigger the difference in EN, more polar the bond