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Elements are arranged in the periodic table in order of increasing atomic number - Scottish Highers Chemistry - Question 1 - 2023
Question 1
Elements are arranged in the periodic table in order of increasing atomic number. Many physical and chemical properties of the elements show periodic trends. (a) Fi... show full transcript
Worked Solution & Example Answer:Elements are arranged in the periodic table in order of increasing atomic number - Scottish Highers Chemistry - Question 1 - 2023
Step 1
Explain why there is an increase in first ionisation energy from elements d to k in the diagram.
Answer
The increase in first ionisation energy from elements d to k can be attributed to the greater nuclear charge experienced by the outer electrons. As we move from d to k, the number of protons in the nucleus increases, resulting in a stronger attractive force on the electrons. This means that more energy is required to remove an electron from the outer shell.
Step 2
Step 3
Explain fully the large increase between the first and second ionisation energies of sodium.
Answer
The large increase between the first and second ionisation energies of sodium can be explained by the removal of different shells of electrons. The first ionisation removes one electron from the outer shell, resulting in a Na<sup>+</sup> ion. However, removing the second electron involves removing it from a full inner shell, which is much closer to the nucleus and more stable. This requires significantly more energy due to the increased attraction from the larger effective nuclear charge experienced by the electron being removed.
Step 4
Use the information in the table to determine the enthalpy change, in kJ mol<sup>-1</sup>, for the following reaction.
Answer
The enthalpy change for the reaction can be calculated by taking the difference between the second and first ionisation energies. Therefore, the enthalpy change = 4562 kJ mol<sup>-1</sup> (second) - 496 kJ mol<sup>-1</sup> (first) = 4066 kJ mol<sup>-1</sup>.
Step 5
Step 6
Explain fully why electronegativity decreases going down a group.
Answer
Electronegativity decreases going down a group due to the increased distance between the nucleus and the valence electrons as additional electron shells are added. This increases electron shielding, which reduces the effective nuclear charge felt by the valence electrons and, therefore, their ability to attract bonding electrons.
Step 7