topic 1- atomic structure and periodic table Flashcards
State what is meant by two arrows in the same box when expressing electronic configuration? (1)
electrons with opposite spin or two electrons in the same orbital with opposite spin
explain why iodine and chlorine have many similar chemical reactions (2)
iodine also has 7 electrons in its outer shell
electron configurations/number of electrons in the outer shell govern their chemical reactions
explain why the first ionisation energy of magnesium is higher than that of sodium (3)
nuclear charge
magnesium has more protons/ has a great nuclear charge than sodium
Shielding
Shielding in mg similar to shielding in na
attraction
so the force of attraction between the nucleus and the outer electron is greater in magnesium
write the equation, including state symbols, to show the third ionisation energy of magnesium (1)
Mg2+ (g) —> Mg3+ (g) + e-
a student suggested that the difference in the rates of reaction of strontium and barium with water is due to the difference in the sum of their first and second ionisation energies.
discuss this suggestion. (6)
barium loses its outer electrons more easily
barium has a larger atomic radius
barium has more shielding
this outweighs barium’s greater nuclear charge
barium reacts faster/is more reactive
Explain the trend in the values of the first ionisation energies for group 6 (3)
first ionisation energy decreases down the group because although the number of protons is increasing
the electron being removed is further from the nucleus
giving more shielding from the nucleus
explain why the first ionisation energy of sulphur is lower than that of chlorine (2)
because in sulphur the nuclear charge is less
and the electron being removed is from the same sub-shell
explain why the first ionisation energy of sulphur is lower than that of phosphorus (2)
in sulphur the electron is being removed from an orbital containing two electrons
(resulting in an increase in) repulsion between electrons (so electrons lost more easily)
the sequence of the first three elements in the periodic table in hydrogen, helium and then lithium.
explain why the first ionisation energy of hydrogen is less than that of helium, but greater than that of lithium (4)
H < He
He has a greater nuclear charge than H
in helium the outer electrons lost is in the same shell as hydrogen
H > Li
in lithium the outer electrons lost is further from the nucleus
and is shielded by inner electrons
explain why the first ionisation energy of sodium is greater than that of potassium (3)
the outer electrons lost in a sodium atom is closer to the nucleus
less shielding from inner electron shells
these outweigh the greater nuclear charge in potassium
explain why the difference between the second and third ionisation energies of calcium is much larger than the difference between the first and second ionisation energies (2)
the third electron is lost from a shell closer to the nucleus
first and second electrons removed from the same shell (so experience similar shielding)
give a reason why the logarithm of the ionisation energy, rather than just the ionisation energy, is used to plot a graph (1)
the range of numbers is too large to fit on a graph
logarithms make it easier to plot the numbers
give a reason why the successive ionisation energies increase (1)
same number of protons is attracting a decreasing number of electrons
electron is removed from an increasingly positively charged ion
electron removed is closer to the nucleus
the electron removed is experiencing less electron-electron repulsion
state what is meant by the term first ionisation energy (3)
energy required
to remove an electron
from one mole
of gaseous atoms
Explain why the first ionisation energy of oxygen is lower than that of nitrogen (3)
oxygen loses a paired electron/electron lost from a full orbital
nitrogen loses an electrons from a singly occupied orbital/ half-filled subshell
there is more repulsion between paired electrons
State what is meant by the term relative atomic mass (2)
the average/mean mass of an atom of an element
compared to 1/12th the mass of an atom of carbon-12
give the reason why, despite the difference in atomic structure, isotopes have the same chemical reactions (1)
they have the same electronic configuration/structure
state how the relative abundance of two isotopes can be found (2)
compare the intensity of signal/number of particles of each isotope detected
in a mass spectrometer
state what is meant by the terms ‘relative isotopic mass‘ and ‘relative atomic mass’ (3)
relative isotopic mass refers to the mass of an atom of that isotope
relative atomic mass refers to the weighted average/mean mass of an atom
both are relative to 1/12th the mass of a c-12 atom
state what is meant by the term isotopes (1)
atoms with the same number of protons but different numbers of neutrons
give a reason why the mass spectrometer must be operated under vacuum (1)
to prevent collisions with gas/air molecules/particles (that would deflect the ions)
Give the meaning of the term ‘periodicity’
Illustrate your answer by referring to the atomic radii of the period 2 and 3 elements. (3)
a trend/pattern of repeating (physical and chemical) properties (with increasing atomic number)
atomic radii decrease from left to right/ across the period
the pattern/atomic radium trend is repeated in period 3
Hydrogen can be placed in several different positions in periodic tables. One is immediately above lithium in Group 1. Another is in the centre of the first row, as shown in the Periodic Table on the back cover. Criticise the position of hydrogen immediately above lithium by giving one reason in favour and two against. (3)
electronic structure of hydrogen is 1s1/has one electron in s orbital
the rest of group 1 are (Alkali) metals (hydrogen is not)
hydrogen does not react in the same was as the rest of group 1/ has different chemical properties
froms a H- ions
explain the trend in melting temperatures across the elements of period 2 in terms of their structure and bonding (6)
Li to Be the bonding is metallic
metallic bonding gets stronger as the charge on the cation decreases
B and C have a giant structure of atoms
a lot of energy is needed to break (strong) covalent bonds, (in graphite and diamond)
N to Ne are simple molecules
weak London forces between molecules
A student stated that ‘the elements scandium and zinc are d-block elements but are not transition metals’.
Discuss this statement, using appropriate electronic configurations to support your answer. (4)
both elements have the last added electron in the d-sub shell/orbital
but neither forms a (stable) ion with an incomplete d orbital
electronic configuration for zinc ion and scandium ion
A student suggested that the difference in the rates of reaction of strontium and
barium with water is due to the difference in the sum of their first and second
ionisation energies. Discuss this suggestion.
(6)
- the sum of the first two ionisation energies for barium is
lower / barium loses (its outer) electrons more easily - barium is a bigger atom/barium has a larger atomic
radius/barium has more shells of electrons - barium has more shielding
- these outweigh/exert a greater influence than
- barium has more proton/greater nuclear charge
- barium reacts faster/barium is more reactive
cliticise the position of hydrogen being immediately above lithium by giving one reason in favour and 2 againts
- forms a H- ion
- rest of group 1 are metals
- electronic structure of hydrogen is S1
- hydrogen reacts differently to group 1 and has different chemical properties
in terms of atomic structure, give two reasons why oxygen is more electronegative than carbon
- more protons /greater nuclear charge
- has a smaller atomic radius than carbon atoms
