periodicity, structure and bonding in elements Flashcards
(23 cards)
what’s covelant radius
measure of the size of an atom
- can be explained by no of occupied shells and nuclear charge
what’s the first ionisation energy
energy required to remove one mole of electrons from one mole of the gaseous atoms
what’s the seconds and further ionisation energies
energies required to remove further moles of electrons
trends in ionisation and electronegativity can be measured by…
atomic size, nuclear charge and screening effect
what’s electronegativity
measure of the attraction an atoms involved in a bond has for the atoms in the bond
metallic elements
- good conductors of heat and electricity due to presence of delocalised electrons
- high mp and bp indicating strong
- high density - atoms closely packed
what’s the relationship between no of outer electrons and strength of metallic bonding
more outer electrons –> stronger bonding
monatomic
atoms that don’t form bonds with other atoms
when are LDF detectable
at low temp when the atoms have low kinetic energy and close to each other
how is LDF formed
- electrons are uniformly distributed over the volume of the atom due to the continual movement of electrons
- this results in one side having a slight positive charge and the other having a slight negative charge
how is an induced temp dipole formed
- when atom w temp dipole is close to another atom affecting the distribution of atoms in the neural atom
- slight negative charge of temp dipole repels electrons on neutral atom pushing them to other side of atom
- results in formation of temp dipole
why do boiling points increase going down a group
more electrons give a bigger temp dipole causing them to require stronger LDF. more energy is required to overcome them
covenant energy structure
lattice, regular repeating pattern
- requires a lot of energy to break the bonds resulting in high mp and bp
the 3 elements that have covenant network structure
boron network, carbon (Dimond) network, silicon network, graphite
difference between graphite and Dimond
graphite:
- soft and can more paper, due to layers of carbon being able to slide over each other as weak LDF are broken
- can conduct electricity due to delocalised electrons
Dimond:
- doesn’t conduct as outer electrons used to make covenant bonds
- very hard due to the covelant bonding extending in 3 dimensions
periodicity
the repeating pattern of chemical and physical properties
as nuclear charge increases
the electrons feel a greater pull from nucleus
as no of occupied electron shells increase
outermost electrons become further away from nucleus
why do atoms get smaller across a period
bc the electron shells containing electrons remains the same and positive charge of nucleus increases
- increased positive charge pulls electrons closer to nucleus
ionic radius
distance between nucleus and electron in the outermost shell
going down a group…
increasing covelant radii
increasing ionic radii
decreasing first ionisation energy
decreasing electronegativity
going across a row…
decreasing covelant radii
decreasing ionic radii
increasing first ionisation energy
increasing electronegativity
Why is there a decrease in the size of atoms across the period from aluminium to sulfur
increasing nuclear charge
