periodic table and energy Flashcards
what is the periodic table? (3)
the arrangement of elements by:
1) increasing atomic (proton) number
2) periods showing repeating trends in physical and chemical properties (periodicity)
3) in groups having similar chemical properties
what is the definition of first ionisation energy?
energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous + ions.
what does ionisation energy measure?
measures how easily an atom loses electrons to form positive ions
what factors affect ionisation energy? (3)
1) no. of electron shells/ atomic radius
2) nuclear charge
3) electron shielding (inner electron shells blocking charge from the nucleus)
what is the first ionisation energy equation for sodium?
Na (g) –> Na+(g) + e-
what is the general rule in successive ionisation energies?
no. of electrons = ionisation energies
every time an electron is removed… (3) (successive ionisation energy)
1) there is a greater nuclear attraction
2) atomic radius is slightly smaller
3) successive ionisation energies will increase
how can you tell the electronic structure of an element from data which gives ionisation number and energies? (2)
1) name where the jump in energy occurs
2) say how many electrons are in its outer shell from that
what do trends in 1st ionisation energy provide evidence for?
the existence of shells and sub shells
what is the trend in first ionisation energies down a group? (3)
1) first ionisation energy decreases down a group
2) atomic radius increases down a group
3) so shielding increases meaning it is easier for the electron to be lost as attraction is weaker between the nucleus and electron
what is the trend in first ionisation energies across period 2? (3)
1) general increasing trend along the period
2) due to decreasing atomic radius and increasing nuclear charge meaning outer electrons are held more strongly
3) which requires more energy to overcome
why is boron an exception to the trend in first ionisation energy across period 2? (2)
1) Boron has a lower first ionisation energy than expected due to the energy difference between 2s and 2p sub shells / new sub shell shielding
2) the electron is being removed from a higher energy level that is further from the nucleus so the electron is held less strongly.
why is oxygen an exception to the trend in first ionisation energy across period 2? (3)
1) oxygen has a lower first ionisation energy than expected by the general trend due to repulsion within the 2p orbital
2) two electrons with opposite spins are placed in the same orbital
3) allows electron to be removed from oxygen more easily as the repulsion is destabilising
what is the trend in first ionisation energies across period 3? (3)
1) general increasing trend
2) due to decreasing atomic radius and increasing nuclear charge
3) meaning outer electrons are held more strongly
why is aluminium an exception to the trend in first ionisation energy across period 3? (3)
1) aluminium has a lower first ionisation energy due to the energy difference between the 3s and 3p sub shells
2) the electron is being removed at a higher energy level which is further away from the nucleus
3) held less strongly so requires less energy to remove
why is sulfur an exception to the trend in first ionisation energy across period 3? (3)
1) lower first ionisation energy than expected due to the electron repulsion in the 3p sub shell
2) electrons with opposite spins held in the same orbital
3) allows electron to be removed from sulfur more easily as the repulsion is destabilising
what is the general trend for first ionisation energy down a group? (3)
1) first ionisation energy decreases down a group
2) more electron shells lead to increasing atomic radius so weaker nuclear attraction
3) shielding also increases down a group which further reduces attraction
what is the general trend for first ionisation energy across a period? (4)
1) first ionisation energy increases across a period
2) due to a decreasing atomic radius due to extra nuclear charge
3) greater nuclear attraction to overcome
4) more nuclear charge because of an extra proton
what 3 things affect first ionisation energy? describe the trend in these across a group and down a period (3)
1) atomic radius (increases down a group, decreases across a period)
2) nuclear charge (increases across a period, decreases down a group)
3) shielding (constant across a period, increases down a group)
why does shielding remain constant across a period?
the number of energy levels is the same
why does atomic radius decrease across a period? (2)
1) elements gain an extra proton for the same number of electron shells, which increases nuclear charge
2) attracting the electron closer which decreases atomic radius
how are atomic radius and nuclear charge linked?
A higher nuclear charge causes greater attractions to the electrons, pulling the electron shells closer to the nucleus which results in a smaller atomic radius.
what is the periodic trend in electron configurations across Periods 2 and 3? (2)
1) across period 2, the 2s sub shell fills with 2 electrons and then the 2p subs shells fill with 6 electrons
2) in period 3 the pattern repeats itself with the 3s and 3p sub-shells.
How are elements classified into SPDF block elements?
classification is based on the name of orbitals which receive the last electron.