U1- Electron arrangement and the periodic table Flashcards
*atomic radius
half the distance between two nuclei of a diatomic molecule, assuming a single covalent bond between two identical atoms
core charge ( + calc)
measure of the net attractive force felt by valence shell electrons towards the nucleus
no. of protons in nucleus - no. of electrons in then inner shell
how does core charge change across a period explanation
increases because as you go across the period, nuclear charge increases but electron shielding doesn’t change t/f increased attraction between valence e and nucleus
how does core charge change down a group
stays the same because while nuclear charge increases, electron shielding equally increases
*electronegativity
the strength with which atoms of an element attract electrons when they are chemically combined with another element
(large imbalances could result in covalent bond polarity or ion formation)
how does atomic radius change across a period
decreases because core charge increases while the number of occupied electron shell stays the same t/f increased attraction of valence electrons to the nucleus
electronegativity is higher when….
the atomic radius is low
and
the core charge on the atom is high (should be split up into nuclear charge and electron shielding)
electronic configuration of copper
1s2 2s2 2p6 3s2 3p6 4s1 3d10
electron configuration of chromium
1s2 2s2 2p6 3s2 3p6 4s1 3d5
Hund’s Rule
Hund’s Rule of Maximum Multiplicity:
electrons in a partially filled sub shell will arrange themselves so as to form the maximum number of half filled orbitals
Aufbau Principle
sub shells are filled in order from lowest energy to highest energy and that lower-energy sub shell will be filled completely before elections move into a higher-energy sub shell
Pauli’s Exclusion Principle
only a max of 2 e in a given orbital and electrons will have opposite spin if orbital is filled
*orbital
region of space in which up to two electrons are likely to be located. Orbitals may also be empty
Bohr model of the atom
an electron in a given orbit has constant energy and
can only occupy fixed energy levels (cannot exist between two levels)
electron shielding
the repulsive force exerted by inner shell electrons on outer shell electrons pushing them away from the nucleus
sub shell
a subdivision of an electron shell containing a fixed no. of orbitals at the same energy level
how many orbitals can each sub shell hold
s- 1 (spherical shape)
p-3 (petal shape)
d-5
f-7
how does the light emission spectra work?
as an element is heated, electrons absorb energy and can be promoted to an excited state
when electron relapses to ground state a photon is released
electrons can return via different pathways each producing its own particular wavelength in the electron spectrum
the more electrons, the more relapse pathways possible
how does atomic radius change down a group
increases because core charge stays the same while the number of occupied electron shell increases t/f decreased attraction
how does electronegativity change across a period
increases because core charge increases while the number of occupied electron shell stays the same thus the atomic radius decreases t/f increased attraction between valence electrons and the nucleus
how does 1st ionisation energy change across a period
increases because core charge increases while the number of occupied electron shell stays the same thus the atomic radius decreases, causing valence e to be more strongly attracted to the nucleus t/f more energy is required to remove an electron
how does reactivity in metals change across a period
decreases because core charge increases while the number of occupied electron shell stays the same t/f increased attraction between valence e and the nucleus thus general increase in energy required to remove an electron
how does reactivity in non metals change across a period
increases because core charge increases while the number of occupied electron shell stays the same thus the atomic radius decreases t/f increased attraction between valence e and the nucleus
how does electronegativity change down a group
decreases because while core charge stays the same, the number of occupied electron shells increases, increasing the atomic radius t/f attraction decreases between valence electrons and the nucleus
how does 1st ionisation energy change down a group
decreases because while core charge stays the same, the number of occupied electron shells increases, increasing the atomic radius as attraction between valence electrons and the nucleus decreases t/f less energy is required to remove an electron
how does reactivity in metals change down a group
increases because while core charge stays the same, the number of occupied electron shells increases, increasing the atomic radius t/f attraction decreases resulting in general decrease in the energy required to remove an e
how does reactivity in non-metals change down a group
decreases because while core charge stays the same, the number of occupied electron shells increases, increasing the atomic radius t/f attraction decreases
*first ionisation energy
the amount of energy required to remove an electron form each of a mole of gaseous atoms (kJ mol-1)
which group has the highest 1st ionisation energy and why
noble gases/ g18/ g8 because they have the highest core charge of all the elements in the same period t/f smallest atomic radius
*relative isotopic mass
mass of tat isotope relative to 1/12 of the mass oof an atom of carbon-12 (ratio)
relative atomic mass
average mass of isotopes of that element weighted for their abundance relative to 1/12 of the mass of an atom of carbon-12
why does relative isotopic mass have no units
because it compares the mass of an atom of an isotope to the mass of an atom of carbon-12 as 12 units exactly, then this means that it is a ratio and therefore has no units
why do alloys composed of nanoparticles produce much stronger materials
bc nanoparticles have a very large surface area to volume ration, them the strength of inter particle bonding increases while the spaces between particles decrease therefore creating a stronger alloy
why do atomic radii moving across a period stay the same for transition metals eg actinides
bc e is added to the inner shell therefore while nuclear charge increases, electron shielding increases therefore cc stays the same tf atomic radii stays the same
