PERIODICITY Flashcards
Periodic table allows chemists to make predictions about
reactivity
physical properties
type of bonding
Metallic Bonding
Between atoms of metal elements (Li, Be, Na, Mg, Al, K, Ca). Outer electrons delocalised which produces an electrostatic force of attrition between positive metal ions and negative delocalised electrons.
Why can metallic bonds conduct
Delocalised electrons
Covalent molecules
Discrete covalent are small groups held together by strong covalent bonds inside and weak intermolecular forces between molecules.
Shared pair of electrons electrostatically attached to positive nuclei of 2 NON METAL atoms.
Achieve stable outer electron arrangement by sharing electrons
Discrete Covalent Examples
Diatomic NOFCH
P4
S8
C60 - fullerenes
Covalent networks
Large, rigid 3D arrangement of atoms held together by strong covalent bonds.
High melting points because only contain strong bonds
Covalent network example
Boron, Carbon, Sillicon
diamond and graphite (only one that conducts)
Monatomic elements
Group 0 (noble gases) exist as single unattached particles. Stable with full outer shell.
Low mp/bp as easily separated by overcoming weak LDF
Summary of bonding density, mp, conduction
Monatomic - low - low - no
Molecular - low - low - no
Network - v high - v high - no but graphite
Metallic lattice - high - high - yes
covalent radius
measure of how large individual atoms are
period - decrease (nuclear charge)
group - increase (more outer electrons/screening)
Ionisation energy
Energy involved in removing one mole of electrons from one mole of atoms at a gaseous state
period - increase (greater no protons)
group - decrease (more electron shells/shielding)
Ionisation energy example
Mg (g) —-> Mg+(g) + e-
Mg+(g) —-> Mg2+(g) + e-
Electronegativity
Measure of atom’s attraction for electrons in a bond
Period - increase (higher nuclear charge and smaller radius)
Group - decrease ( increase radius and extra energy levels/screening)
Highest element electronegativity
Fluorine
