Summary IB Chemistry chapter 3: PERIODICITY

PERIODICITY

Metals
● Conductors
● Malleable
● Ductile
● Lustrous

Non-metals
● Conductors
● Brittle
● Non lustrous
Metalloids
● Solid at room temperature
● Semiconductors
● Has metallic and non metallic properties




Periodic trends
Effective nuclear charge: The net positive charge experience by an electron
in an atom
- Increases across a period
- Decreases down a group
Atomic radius: Half the distance between the nuclei of two covalently
bonded atoms
- Decreases across a period
- Increases down a group
Ionic radius: The distance between the nucleus and valence electrons in an
ion
- Cations have a smaller ionic radius than their atomic radius
- Anions have a larger ionic radius than their atomic radius

, - Decreases across a period
- Increases down a group
Ionization energy: Minimum amount of energy needed to remove one mol
of electron from an atom in its gaseous state
- Increases across a period
- Decreases down a group
Electron affinity: The energy change when one mol of electron is added to
an atom in its gaseous state
- 1st electron affinity is exothermic
- 2nd electron affinity is endothermic
- Increases across a period
- Decreases down a group
Electronegativity: Ability of a nucleus to attract a pair of covalently bonded
electrons
- Increases across a period
- Decreases down a group


Melting point across period 3
● Melting point depends on the structure and bonding
● Na, Mg and Al = metallic bonding (increases across a period)
● Si = Giant covalent bonding
● P, S, Cl, Ar = Weak intermolecular forces (London dispersion,
increases with increasing molar mass)