Unit 1 Flashcards
First ionisation energy
the energy required to remove one mole of electrons from one mole of gaseous atoms
What type of reaction is ionisation energy
endothermic (positive) as it requires energy to break electrostatic attraction.
Trend in ionisation energy across the period
increases- increased nuclear charge, more energy required to remove electrons.
trend in ionisation energy down a group
decreases- increasing electron shells, inner shells shield outer shells from nuclear charge meaning less energy required to remove electron.
Why might the second ionisition energy of an atom be much higher than the first?
because an electron is being removed from a full, stable shell that is closer to the nucleus
Definition of covalent radii
half the distance between the nuclei of two covalenty bonded atoms
Trend in covalent radii across the period
decrease- increasing nuclear charge which pulls electron shells more closer to the nucleus
Trend in covalent radii down a group
increases- increasing electron shells
Definition of electronegativity
the measure of attraction an atom involved in a bond has for the electrons in that bond
Trend in electronegativity across the period
increases- nuclear charge increases which creates a stronger electrostatic attraction, electrons held more tightly
Trend in electronegativity down a group
decreases- increasing electron shells. inner shells shield outer shells from nuclear charge, electrons further from nucleus
What is metalic bonding?
positive metal ions surrounded by a sea of delocalised electrons
What are the properties of metalic bonding?
- lattice= hight mp and bp.
- can conduct due to delocalised electrons
What is covalent bonding?
shared pair of electrons between atoms.
What are the properties of covalent molecular bonding?
- discrete= low mp and bp
- weak intermolecular forces
- doesn’t conduct
What are the properties of covalent network bonding?
- network= high mp and bp
- strong covalent bonds
- doesn’t conduct (except graphite)
What is ionic bonding?
attraction between positive and negative ions
What are the properties of ionic bonding?
- lattice= high mp and bp
- free ions
- conduct when molten or in solution
What is intramolecular bonding?
forces within the molecule (covalent, ionic etc)
What is intermolecular bonding?
forces between molecules (LDF, pd-pd, hydrogen)
What bonding is there in the first 20 elements?
COVALENT MOLECULAR= diatomic (gas), P4, S8, fullerencs (C60)
METALIC= group 1 (except H), group 2, aluminium.
MONATOMIC= group 8/0
COVALENT NETWORK= Boron, Carbin, Silicon
LDF properties
-weakest
- Arise due to an uneven distribution of electrons, causing temorary dipoles, then causing induced dipoles in neighbouring atoms
- more electrons= stronger LDF
List the types if intermolecular bonding from weakest to strongest
LDF, Pd-Pd, Hydrogen
Pd-Pd properties
- stronger than LDF’s
- Arises when theres a difference in electronegativity
- can also arise due to an uneven structure
- Higher mp and bp
