chapter 7 periodicity Flashcards
(32 cards)
how are elements arranged in the morden periodic table?
arranged in order of atomic number in 7 periods and 18 groups
how was the early periodic table arranged?
in order of atomic mass by mendeleev who also grouped elements with similar properties together and left gaps for elements yet to be discovered
what is periodicity?
a repeating trend in properties of the elements across each period of the periodic table.
what properties are considered in periodicity?
electron configuration, ionisation energy, structure, melting points.
why do elements in the same group tend to have similar properties?
same number of electrons in outer shell
how are the blocks of the periodic table named?
they are called S-block/P-block/D-block/F-block as their outermost electron is in the corresponding lettered sub shell
what are the specific names for some groups?
group 1 - alkali metals
group 2 - alkaline earth metals
groups 3-12 - transition metals
group 17 - halogens
group 18 - noble gases
state the outer shell electron configuration for a group 13 element?
nS2, nP1
state the general outer electron configuration for lead.
nS2, (n-2)F14, (n-1)D10, nP2
what is ionisation energy?
it measures how easily an atom loses electrons to form positive ions
what is first ionisation energy?
the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of 1+ ions
write the second and third ionisation energies for calcium.
Ca^+(g) -> Ca^2+(g) + e-
Ca^2+(g) -> Ca^3+(g) + e-
which electron is lost first and what are the factors affecting I.E?
the outermost electron will be lost first as it experiences the least attraction and the factors effecting this are: atomic radius, nuclear charge, electron shielding.
what is the general trend in ionisation energy down a group?
atomic radius increases, nuclear attraction decreases, shielding increases so first I.E. decreases
what is the general trend in ionisation energy across a period?
nuclear charge increases, shielding stays the same, atomic radius decreases so attraction increases and first I.E. increases
how many successive ionisation energies are there and why does each one increase from the last?
there are as many I.E.s as there are electrons in an atom and they increase because each time an electron is lost nuclear attraction increases because the protons in the nucleus have the same force but have to attract less electrons
what does a major increase from the previous ionisation energy mean?
a major increase shows that a main principle electron shell has been lost.
why are there some decreases in first I.E across the second period and where are they?
Be/B because boron is the first element in the second period to have electrons in the 2p subshell so is slightly shielded by the 2s subshell.
N/O because oxygen is the first element in the 2p subshell to have paired electrons so the electrons repel each other which makes it easier to lose
what is ionic bonding?
the electrostatic force of attraction between +/- ions.
what is covalent bonding?
the strong electrostatic force of attraction between the positive nuclei of bonded atoms and the shared pair of electrons.
what is metallic bonding?
the electrostatic force of attraction between positive metal ions and delocalised electrons.
describe the electrical conductivity of ionic compounds.
they cannot conduct electricity in solid form because the charged ions are in fixed lattice positions. however when molten or dissolved they can conduct electricity because the ions are free to move so can carry charge.
compare the electrical conductivity of diamond and graphite.
diamond is an allotrope of carbon where each carbon atom is bonded to 4 other carbon atoms so there are no delocalised electrons meaning it cannot conduct electricity. however graphite is an allotrope of carbon where each carbon atom is bonded to 3 other carbon atoms so there are delocalised electrons present to carry charge meaning it can conduct electricity.
do metals conduct electricity?
yes they have delocalised electrons
