3.1 Periodicity Flashcards
What is periodicity ?
Repeating trend in properties of the elements.
How does nuclear charge change as you go across a period ?
Nuclear charge increases as there is +1 proton as you pass across the elements. This increases attraction between valence electron and nuclei.
How does electronegativity change as you go across and up the period band groups ?
Electronegativity increases. Fluorine has the highest electronegativity value.
How does atomic radius change down a group ?
Atomic radius increases because there are more shells so increased distance between valence electron and the nucleus.
How does atomic radius change across a period ?
Decreases across a period as there are more protons which increase the attraction between electrons and nucleus as nuclear charge is greater, so size of atom is smaller.
What is the structure and bonding of a giant metallic lattice ?
Contains regular arranged cations surrounded by delocalised electrons. Has a high melting point of large amounts of energy is required to overcome attraction between cations and delocalised electrons.
What is the structure and bonding of a giant covalent structure ?
Carbon atoms are bonded to 4 other carbon atoms so there are no free electrons to conduct electricity. High melting point as lots of energy required to break covalent bonds.
What is the structure and bonding of simple molecular substances ?
Atoms are covalently bonded. Has low melting point as intermolecular forces don’t require lots of energy to break London forces.
What forces are there in group 0 elements ?
London forces between atoms.
What is the 1st ionisation energy ?
The energy required to remove the least firmly bound electron from each atom in 1 mole of gaseous atoms.
Equation for 1st ionisation energy
Eg., Mg (g) = Mg+ (g) + e-
What is the 2nd ionisation energy ?
Energy required to remove the second least firmly bound electron from each ion in 1 mole of gaseous ions.
Equation for 2nd ionisation energy
Mg+ (g) = Mg2+ + e-
General trends in ionisation energy
There is an increase in energy needed for successful ionisations. This is because generally electrons are removed, so the attraction between the nuclei and the electrons gets bigger, making the ion smaller.
Sudden jump in trend in ionisation energy
Jump in trend is due to electron removed from different shell closer to the nucleus.
What changes to ionisation energy down the group ?
Ionisation energy decreases down the group as there is more shells and electrons being removed is further from the nucleus so attraction is less as there is more shielding.
How does nuclear charge change across a period ?
Nuclear charge increase across a period as they gain a proton so attraction between nuclei and shell is greater so atom is smaller. This requires more ionisation energy.
What is an anomalous property in terms of type of electrons for ionisation energy ?
Removal of the p-electron is higher in energy in boron than the s-electron removed from beryllium. So the 4s sub shell has lower energy than the 3d sub shell.
What is an anomalous property in terms of paired electrons in ionisation energy ?
Oxygen has a paired electron (1s2 2s2 2p4) which requires less energy than removing an unpaired p electron in Nitrogen (1s2 2s2 2p3). This is due to repulsion theory.
Melting/boiling point of giant metallic lattice
Lots of energy required to break electrostatic attraction between cations and delocalised electrons.
Can giant metallic lattices conduct electricity ?
Can conduct as delocalised elections can move carrying charge.
Are giant metallic lattices malleable and ductile ?
Yes as layers of metal cation can slide over each other.
Are giant metallic lattices soluble ?
No as interactions with water and solvents would lead to reactions not dissolving.
Structure of Diamond as a giant covalent structure
Diamond is a tetrahedral shape with bond angles of 109.5. A carbon atom forms 4 bonds with other carbon atoms, so. o free electrons.
Structure of Graphite as a giant covalent structure
Graphite is a trigonal plane shape with bond angles of 120. A carbon atoms forms 3 bonds with other carbon atoms, so has free electrons.
Melting/boiling point of giant covalent structures
Intermolecular forces require little energy to break. However covalent bonds require large amounts of energy to break.
Can giant covalent structures conduct electricity ?
Doesn’t conduct except in graphene and graphite as they only form 3 bonds so have electrons that can move.
Are giant covalent structures soluble ?
Insoluble in almost all solvents as covalent bonds are too strong to be broken by the solvent.
