CHEM1011 Study Set – Threshold Questions With Complete Solutions

How is the wavelength of a photon related to its energy, frequency and wavenumber? correct answer: Energy - As the wavelength is shorter, there is more energy and vice versa Frequency - The frequency of photon increase, causing the wavelength to go down and vice versa Wavenumber - Is reciprocal to the wave length (1/a) Why are energy levels descrete correct answer: Because each energy level has its own energy pathway. How to calculate the wavelengths of light from one energy level to another energy level. correct answer: Use the formula 1/λ = RH(1/n^(first) - 1/n^2(second)) - Remember when an atom is ionising n=infinity What is the energy, in J, of the n = 2 level of the electron in the H atom, compared to the ground electronic state? correct answer: ANS: 1.63 x 10x^-18 J when a question asks for Determine which electronic transitions in the Balmer series (n1 = 2) of the H atom emit light in the ultraviolet region ( < 380 nm) of the electromagnetic spectrum. correct answer: Use Rydberg formula, and find n2 value. MAKE SURE TO CONVERT WAVELENGTH FROM NM TO METERS (x10^-9) What are nodes in 1D waves correct answer: Points where 'circles' meet on wave. where it crosses over what are nodes on 2d waves correct answer: points along the medium that appear to be standing still. These points, sometimes described as points of no displacement, are referred to as nodes. What is the second ionisation energy of magnesium formula correct answer: Mg⁺ + Energy --> Mg²⁺ + 2e⁻ what is first and second ionisation energy correct answer: First ionization energy: The energy needed to remove the outermost, or highest energy, electron from a neutral atom in the gas phase. Second ionization energy: The energy it takes to remove an electron from a 1+ ion (meaning the atom has already lost one electron and now removing the second). What does it mean when a substance such as Lithium and