IB DP Chemistry Structure 2.2 The covalent model HL Paper 2- Exam Style Questions - New Syllabus
Question
(Electronegativity of iron \(= 1.8\); electronegativity of sulfur \(= 2.6\))
(First ionization energy of iron \(= 762\,\text{kJ mol}^{-1}\); Planck constant \(h = 6.63 \times 10^{-34}\,\text{J s}\); speed of light \(c = 3.00 \times 10^{8}\,\text{m s}^{-1}\); Avogadro constant \(N_A = 6.02 \times 10^{23}\,\text{mol}^{-1}\))
Most-appropriate topic codes (IB Chemistry 2025):
• Structure 2.2: The covalent model — part (b)
• Structure 1.1: Models of the particulate nature of matter — part (c)
• Structure 1.3: Electron configurations — part (d)
▶️ Answer/Explanation
(a)
An element consists of only one type of atom and cannot be chemically broken down into simpler substances.
A compound contains atoms of two or more different elements that are chemically bonded together in a fixed ratio.
(b)
Using electronegativity values from the data booklet, the difference is \(\Delta EN = 2.6 – 1.8 = 0.8\), which lies in the polar covalent range, so electrons are shared unequally.
(c)
Iron is a good conductor of electricity, whereas solid iron(II) sulfide does not conduct electricity.
(d)
Energy per atom \(E = \dfrac{762 \times 10^{3}}{6.02 \times 10^{23}} = 1.27 \times 10^{-18}\,\text{J}\).
Frequency \(f = \dfrac{E}{h} = 1.91 \times 10^{15}\,\text{Hz}\).
Wavelength \(\lambda = \dfrac{c}{f} = 1.57 \times 10^{-7}\,\text{m}\).
\(\boxed{1.57 \times 10^{-7}\,\text{m}}\)