Chemical bonding Flashcards
Ionic bonding
the electrostatic force between cations and anions in an ionic crystal lattice
Covalent bonds
formed when the outer electrons of two atoms are shared
How are atoms between molecules kept together ?
by strong covalent bonds
Van der Waals’ forces
weak forces between molecules
-> intermolecular forces
Types of Van der Waals’ forces
- dipole
- permanent dipole-permanent dipole ( pd-pd forces )
-hydrogen bonding
London dispersion forces ( dipole )
instantaneous dipole-induced dipole ( id-id ) forces
Hydrogen bonding
stronger form of pd-pd force
How are ions formed
by the gain or loss of electrons in atoms
Positive ions ( Cations )
when an atom loses one or more electrons
-> mostly metals
Negative ions ( Anions )
when an atom gains one or more electrons
-> mostly non-metals
Lattice
a regularly repeating arrangement of atoms, molecules or ions in 3-D throughout the whole crystal structure
Ionic bond
the electrostatic attraction between oppositely charged ions ( cations & anions )
Electrovalent bond
Ionic bond
Dot-and-cross diagram
a diagram showing the arrangement of the outer-shell electrons in an ionic/ covalent element/compound
Dot-and-cross diagram structure
- outer shells only
- the charge of the ion is spread only, by using square brackets
- the charge on each ion, shown on the right-hand top corner
Covalent bonding
when two non-metals share one or more pairs of electrons
Single covalent bond / bond pair
the electrostatic attraction between the nuclei of two atoms and a shared pair of electrons
represented by a single line between atoms
ex : Cl-Cl
Lone pair
pairs of electrons in the outer shell of an atom that are not involved in bonding
Double covalent bonding
two shared pairs of electrons bonding 2 atoms together
represented by a double line between atoms
ex : O=O
Dative covalent bonding /
Co-ordinate bonding
the sharing of electrons between two atoms where both the electrons in the bond come from the same atom
Needs for dative bonding
- one atom has a lone pair of electrons
- a second atom to have an unfilled orbital to accept the lone pair
-> electron deficient
Electron deficient
an atom/molecule that has less than its usual share of electrons
Bond energy
the energy required to break one mole of a particular covalent bond in gaseous state
Bond length
the distance between the nuclei of two covalently bonded atoms
Shape & bond angle of a covalently bonded molecule depends on :
- number of pairs of electrons around each atom
- whether these pairs are lone pairs or bonded pairs