chemistry-periodicity Flashcards
Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has
a higher melting point than phosphorus(V) oxide.
4 marker
(1)- silicon oxide has a giant covalent structure
(1)-many strong covalent bonds which require a lot of energy to overcome
(1)-phospohorus oxide is a simple covalent molecule
(1)- it has weak van der Waals between the molecule which are easy to overcome and break easily
This question is about atomic structure.
There is a general trend for an increase in ionisation energy across Period 3. Give one example of an element that deviates from this trend.
Explain why this deviation occurs.
3 marks
(1)- Aluminium
(1)- aluminiums outer electron is in a 3p orbital
(1)- this is slightly more shielded and further away than 3s
Identify element X.
Explain your choice.
3 marker
(1)-phosphorous
(1)-theres a large jump in ionisation energy for the 6th ionisation energy
(1)-this is because the electron is being removed from a lower energy level which is closer to the nucleus
Identify the element in Period 3, from sodium to argon, that has the highest
second ionisation energy.
Give an equation, including state symbols, to show the process that occurs
when the second ionisation energy of this element is measured.
2 marker
(1)- sodium
(1)- Na+(g) - Na2+(g) + e-
Explain why the atomic radius decreases across Period 3, from sodium to
chlorine.
2 marker
(1)- nuclear charge increases
(1)-shielding is similar so electrons are added to same shell
Identify the element in Period 4 with the largest atomic radius.
3 marker
(1)-potassium
(1)- smallest nuclear charge
(1)-similar shielding and same number of shells as other elements in period 4
Explain why the atomic radii of the elements decrease across Period 3
from sodium to chlorine.
2 marker
(1)-nuclear charge increases
(1)- attraction between nucleus and electrons increases as electrons are added to the same shell
Explain why the melting point of sulfur (S8) is greater than that of phosphorus (P4).
2 marker
(1)-s8 molecules are bigger than p4 molecules
(1)- therefore van der Waals forces between molecules are stronger in sulphur
more energy to overcome forces
State the meaning of the term periodicity
1 marker
repeating trends of physical or chemical properties
Explain, in terms of its structure and bonding, why nickel has a high melting
point.
2 marker
(1)-strong metallic bond
(1)-strong attraction between positive metal ions and delocalised negative electrons
Explain why the melting point of magnesium is higher than that of sodium.
3 marker
(1)- mg has more delocalised electrons
(1)-stronger attraction between positive metal ion and delocalised electrons
(1)- smaller ion
State the meaning of the term first ionisation energy of an atom.
2 marker
minimum energy required to remove 1 mole of electrons from 1 mole of atoms in a gaseous state
The Ne atom and the Mg2+ ion have the same number of electrons. Give two
reasons why the first ionisation energy of neon is lower than the third ionisation
energy of magnesium.
2 marker
(1)- mg atom is smaller
(1)- mg has a higher nuclear charge
There is a general trend in the first ionisation energies of the Period 3 elements, Na
– Ar. State and explain this general trend.
3 marker
(1)- increases
(1)- nuclear charge increases
(1)- shielding is the same so electrons are added to the same shell
Explain why the first ionisation energy of sulphur is lower than would be
predicted from the general trend.
2 marker
(1)- reference to electron pair in 3p sub level
(1)- repulsion between electrons in electron pair
In terms of atomic structure, explain why the van der Waals’ forces in liquid argon
are very weak.
2 marker
(1)-argon particles with electrons closer to the nucleus
(1)- cannot be easily polarised
