The following table gives the atomic numbers of elements V, W, X, Y and Z.
| Element |
V |
W |
X |
Y |
Z |
| Atomic number |
11 |
16 |
18 |
19 |
24 |
(a)Which of the elements: (i) belong(s) to group 1?
(ii) is/are riotle gas(es)?
(iii) form(s) coloured compound(s)?
(iv) form(s) an anion?
(v) react(s) with water to liberate hydrogen?
(vi) react(s) with water to form alkaline solution?
(b) What is the:
(i) charge on the ion formed in
(a)(iv) above?
(ii) group of the element(s) in (a)(i) above?
(c)(i) Write the formula of the compound formed between element V and element W.
(ii) Sate the type of bond formed in (c)(i) above. Explain your answer.
(d)(i) What is a covalent compound?
(ii) Give two factors that influence covalent bonding.
(iii) State the type of bond that exists in each of the following substances: MgO, \( \mathrm{NH_3} \) and Fe.
(iv) What are intermolecular forces?
First identify each element from its atomic number, then place it in the Periodic Table.
| Element | Atomic number | Identity | Group / block |
|---|
| V | 11 | Sodium, Na | Group 1 |
| W | 16 | Sulfur, S | Group 6 |
| X | 18 | Argon, Ar | Group 8 (noble gas) |
| Y | 19 | Potassium, K | Group 1 |
| Z | 24 | Chromium, Cr | Transition (d-block) metal |
(a)
- (i) Group 1: V and Y (sodium and potassium). Each has a single electron in its outermost shell.
- (ii) Noble gas: X (argon). Its electron configuration 2,8,8 is a complete, stable octet.
- (iii) Coloured compound(s): Z (chromium). Transition metals have partly filled d-orbitals, so d-d electron transitions absorb visible light and give coloured compounds.
- (iv) Forms an anion: W (sulfur). With 6 outer electrons it gains 2 electrons to complete its octet, forming S2-.
- (v) Reacts with water to liberate hydrogen: V and Y (sodium and potassium).
- (vi) Reacts with water to form an alkaline solution: V and Y. They form NaOH and KOH respectively, which are alkalis.
The reaction of a Group 1 metal with water is illustrated by:
\[2\text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq) + \text{H}_2(g)\]
(b)
- (i) The ion in (a)(iv) is the sulfide ion S2-; its charge is 2- (a double negative charge).
- (ii) The elements in (a)(i) belong to Group 1.
(c)
- (i) V is Na (forms Na+) and W is S (forms S2-). Balancing the charges gives the formula Na2S.
- (ii) The bond is ionic (electrovalent). Sodium, a Group 1 metal, loses one electron to become Na+; sulfur, a Group 6 non-metal, gains two electrons to become S2-. The complete transfer of electrons from the metal to the non-metal, and the strong electrostatic attraction between the oppositely charged ions, is the mark of ionic bonding.
(d)
- (i) A covalent compound is a compound in which the atoms are held together by the sharing of one or more pairs of electrons, usually between non-metallic atoms.
- (ii) Two factors that influence covalent bonding:
- High ionisation energy of the combining atoms (they hold their electrons too tightly to transfer them, so they share instead).
- A small difference in electronegativity between the atoms (electrons are shared rather than fully transferred).
- (iii) Type of bond in each substance:
| Substance | Bond type |
|---|
| MgO | Ionic (electrovalent) |
| NH3 | Covalent |
| Fe | Metallic |
- (iv) Intermolecular forces are the relatively weak forces of attraction that exist between separate molecules of a substance, as distinct from the strong bonds that hold atoms together within a molecule.
First identify each element from its atomic number, then place it in the Periodic Table.
| Element | Atomic number | Identity | Group / block |
|---|
| V | 11 | Sodium, Na | Group 1 |
| W | 16 | Sulfur, S | Group 6 |
| X | 18 | Argon, Ar | Group 8 (noble gas) |
| Y | 19 | Potassium, K | Group 1 |
| Z | 24 | Chromium, Cr | Transition (d-block) metal |
(a)
- (i) Group 1: V and Y (sodium and potassium). Each has a single electron in its outermost shell.
- (ii) Noble gas: X (argon). Its electron configuration 2,8,8 is a complete, stable octet.
- (iii) Coloured compound(s): Z (chromium). Transition metals have partly filled d-orbitals, so d-d electron transitions absorb visible light and give coloured compounds.
- (iv) Forms an anion: W (sulfur). With 6 outer electrons it gains 2 electrons to complete its octet, forming S2-.
- (v) Reacts with water to liberate hydrogen: V and Y (sodium and potassium).
- (vi) Reacts with water to form an alkaline solution: V and Y. They form NaOH and KOH respectively, which are alkalis.
The reaction of a Group 1 metal with water is illustrated by:
\[2\text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq) + \text{H}_2(g)\]
(b)
- (i) The ion in (a)(iv) is the sulfide ion S2-; its charge is 2- (a double negative charge).
- (ii) The elements in (a)(i) belong to Group 1.
(c)
- (i) V is Na (forms Na+) and W is S (forms S2-). Balancing the charges gives the formula Na2S.
- (ii) The bond is ionic (electrovalent). Sodium, a Group 1 metal, loses one electron to become Na+; sulfur, a Group 6 non-metal, gains two electrons to become S2-. The complete transfer of electrons from the metal to the non-metal, and the strong electrostatic attraction between the oppositely charged ions, is the mark of ionic bonding.
(d)
- (i) A covalent compound is a compound in which the atoms are held together by the sharing of one or more pairs of electrons, usually between non-metallic atoms.
- (ii) Two factors that influence covalent bonding:
- High ionisation energy of the combining atoms (they hold their electrons too tightly to transfer them, so they share instead).
- A small difference in electronegativity between the atoms (electrons are shared rather than fully transferred).
- (iii) Type of bond in each substance:
| Substance | Bond type |
|---|
| MgO | Ionic (electrovalent) |
| NH3 | Covalent |
| Fe | Metallic |
- (iv) Intermolecular forces are the relatively weak forces of attraction that exist between separate molecules of a substance, as distinct from the strong bonds that hold atoms together within a molecule.
