Periodicity Flashcards
What is periodicity?
Repeating trend in properties across each period.
What is the trend in atomic radius?
Increases down groups as there are more electrons to fill shells of increasing energy and increased distance from nucleus.
Decreases across periods as nuclear charge increases and electrons in same energy shell - closer to nucleus.
What is the first ionisation energy?
Energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions.
What are factors affecting ionisation energy?
Atomic radius - increases, easier to remove electrons so IE decreases
Nuclear charge - increases, IE increase as harder to pull electrons away
Electron shielding - increases, decreased nuclear attraction so IE decreases
Why is the second IE of He greater?
A single electron is pulled closer to the nucleus, so attraction increases and more IE is needed to remove an electron.
Why does Na have a lower 1st IE than Li?
Greater radius and shielding can overcome a greater nuclear charge.
Which groups have electron pair repulsion?
5 and 6
Why are successive ionisation energies useful?
Evidence for different energy levels and allow predictions about the number of electrons in the outer shell, the group of the element and its identity.
What are the trends of IE?
Across a period, IE increases as protons increases, decreasing radius and no extra shielding.
Down a group, IE decreases as easier to remove electrons - extra inner shells so more shielding and further away.
What are exceptions to general IE trends?
Between groups 2 + 3, the p orbital has slighter higher energy than s, so electrons are further from the nucleus and IE decreases.
Between groups 5 + 6, group 5 electrons are lost from a single orbital compared to 2 electrons with repulsion in group 6 so electrons are easier to lose.
What is metallic bonding?
Electrostatic attraction between cations and delocalised electrons.
What is a giant metallic lattice structure?
Network of strong covalent bonds. Metal cations are attracted to electrons, forming a lattice as each ion donates their outer electrons to a pool of electrons. Cations in fixed positions maintain the structure.
What are properties of giant metallic lattices?
- Conduct in solid and liquid as have free electrons
- High melting/boiling point - lots of energy to overcome bonds
- Insoluble but expected charge particles would interact with polar substance (reactions with water)
What is electronegativity?
A bonding atom’s attraction for bonding pairs of electrons in a covalent bond.
What is the trend across periods 2 + 3?
Melting point increases and there is a sharp decrease group 14 + 15, showing the change from giant to simple molecular structures.
