3.1 Periodicity, with exercises

metalloid

elemelons with characteristics of both metals and non metals; physical properties & appearance like metals, chemically more in common with non metals, in PSE form a staircase between metals and non metals, from silicon to polonium

semi conductor

refers to physical properties of materials (including alloys and compounds)

what d block contains

includes transition metals, but not exclusively

what periodicity is reflected in

properties (atomic and ionic radii, IE, EN, electron affinity especially )

what explains these trends

effective nuclear charge

effective nuclear charge trends

increasing across a period, approx the same down a group.

atomic radius trends

increasing down a group (number of occ electron levels increasing), decreasing across a period (eff nuclear charge rising) = significant impact

what ar is measured as

half the distance between neighbouring nucleii in a covalent bond; but can be considered as distance of nucleus to outermost electrons

ionic radius trends

increasing down a group, decreasing across a period

5 ionic radius trends

1. positive ions are smaller than parent atoms due to loss of an occ electron level

2. negative ions are larger than parent atoms due to the addition of an electron to the outer occ electron level = increasing repulsion between the outer electrons

3. decrease from groups 1-14 for positive ions due to increasing effective nuclear charge

4. decrease from groups 14-17 for negative ions due to increasing effective nuclear charge

5. increasing down a group as the number of occ electron levels increases

IE trends

decreasing down a group, increasing across a period

first IE def

amount of energy required to remove one mole of electrons from one mole of gaseous atoms in their ground state

two IE trends

1. increasing across a period due to increasing effective nuclear charge creating a stronger attraction ie making them harder to remove

2. decreasing down a group because removed electron is from the furthest occupied electron level; although nuclear charge increasing, effective nuclear charge stays abt the same due to shielding, and so increasing distance reduces attraction

what indicates attraction to outer electrons except ie

atomic radius

electron affinity def

energy change that occurs when one mole of electrons is added to one mole of gaseous atoms in their ground state