Zadanie 3a
Wzorowane na: Chemistry HL Paper 2, May 2026, TZ2, pytanie 3(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 3a-3c.
Magnesium and sodium are reactive metals with many practical uses.
Polecenie
(i) Describe the structure of solid magnesium and state the forces that hold it together.
(ii) Explain why a piece of magnesium can be hammered into a new shape without breaking.
(iii) Explain why the melting point of magnesium is higher than that of sodium.
(iv) State the electron configuration of the magnesium ion, Mg2+.
(v) Outline why the first ionization energy of boron is lower than that of beryllium.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
(i) Structure: «lattice of» Mg / positive ions / cations AND sea of / delocalized «valence» electrons ✔
Forces: electrostatic attraction «between the cations and the delocalized electrons» ✔
(ii) «layers of» cations slide over each other without breaking the bonding ✔
OR changing the positions of the atoms does not disrupt the bonding / forces of attraction
OR metallic bonds are non-directional
(iii) Mg has the higher charge density «Mg2+ has a higher charge and a smaller radius than Na+; two delocalized electrons per atom instead of one» ✔
stronger metallic bonding / electrostatic forces «in Mg, so more energy is needed to separate the particles» ✔
(iv) 1s2 2s2 2p6 ✔
(v) Be has its outer electrons in the 2s orbital / 1s2 2s2 AND B has an electron in a 2p orbital / 1s2 2s2 2p1 ✔
the 2p orbital has higher energy than 2s «so the electron is easier to remove» OR the 2p electron is more shielded «by the 2s electrons» ✔
Schemat punktowania
(i) [2] M1 lattice of cations AND delocalized electrons; M2 electrostatic attraction; do not accept ‘positive nucleus’ for cations. (ii) [1]. (iii) [2] M1 higher charge density of Mg; M2 stronger metallic bonding; do not accept ‘stronger intermolecular forces’. (iv) [1] accept [He] 2s2 2p6 or [Ne]. (v) [2] M1 sublevels of the outer electrons; M2 higher energy or greater shielding of the 2p electron; accept orbital diagrams showing 2s and 2p for M1.
Komentarz
In (v) the answer rests on the energy of the 2p sublevel; boron has the larger nuclear charge, so an answer based on nuclear charge or atomic radius alone does not explain why the ionization energy is lower.