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Consider the data given in the table about the elements chlorine, argon and potassium - Leaving Cert Chemistry - Question 5 - 2021
Question 5
Consider the data given in the table about the elements chlorine, argon and potassium. | Element | Year discovered | First ionisation energy (kJ mol⁻¹) | Second ion... show full transcript
Worked Solution & Example Answer:Consider the data given in the table about the elements chlorine, argon and potassium - Leaving Cert Chemistry - Question 5 - 2021
Step 1
Why does an individual atom not have a definite boundary?
Answer
An individual atom does not have a definite boundary due to the uncertainty principle. According to this principle, it's impossible to know both the position and velocity (or momentum) of an electron at the same time. This inherent uncertainty means that electrons exist in a probability cloud rather than at fixed positions, leading to an atom lacking a well-defined boundary.
Step 2
How is atomic (covalent) radius defined?
Answer
The atomic (covalent) radius is defined as half of the distance between the nuclei (centers) of two identical atoms when they are bonded together by a single covalent bond. It provides a measure of the size of an atom that forms part of a covalent bond.
Step 3
Step 4
Account for the general decrease in atomic (covalent) radii of the elements down the group and the periodic table from sodium to chlorine.
Answer
The general decrease in atomic (covalent) radii down the group is due to the effective nuclear charge increasing as the number of protons in the nucleus increases. As a result, the atomic number increases, causing the outermost electrons to be pulled closer to the nucleus. Furthermore, the shielding effect becomes less significant as the inner core electrons do not shield effectively against the increased positive charge.
Step 5
Why is establishing an atomic (covalent) radius for argon problematic?
Answer
Establishing an atomic (covalent) radius for argon is problematic because argon is a noble gas and does not readily form covalent bonds. As a result, there are no reliable measurements of bond lengths that could provide a basis for defining its atomic radius.
Step 6
Step 7
Why is the first ionisation energy of potassium lower than that of argon or chlorine?
Answer
The first ionisation energy of potassium is lower than that of argon or chlorine because potassium has its outermost electron in the fourth energy level (shell), which is further away from the nucleus compared to the outer electrons of argon and chlorine. This increased distance results in a weaker attraction from the nucleus, making it easier to remove an electron.
Step 8
Why is the second ionisation energy value for each element in the table bigger than its first ionisation energy value?
Answer
The second ionisation energy value for each element in the table is higher than its first ionisation energy value because after the removal of one electron, the remaining ions have a greater positive charge and hence a stronger attraction to the remaining electrons. Consequently, more energy is required to remove a second electron.
Step 9
Why is the second ionisation energy of potassium very significantly bigger than its first?
Answer
The second ionisation energy of potassium is significantly higher than its first because removing the second electron means removing it from a stable noble gas configuration after the first electron has been removed. This requires significantly more energy due to the increased effective nuclear charge and the reduced electron shielding from the remaining electrons.