Question 1

Define what is meant by electron affinity, and write a balanced chemical equation to represent the relevant process for element Y.

Accepted Answer

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Question 2

In neutral atoms, the 3d orbitals have higher energy than the 4s orbitals.

Accepted Answer

This is due to the increase in electron shielding as the energy level (n) increases, causing the outer 4s orbital to experience less effective nuclear charge than the inner 3d orbitals. As a result, the 4s orbital is filled before the 3d orbitals in neutral atoms.

Question 3

Hund's rule is used to predict the electron configuration of atoms in excited states.

Accepted Answer

Hund's rule is used to determine the ground state electron configurations of atoms and ions by filling degenerate orbitals to maximize the number of unpaired electrons with parallel spins in the same subshell.

Question 4

Elements in which the outermost electron has the same principal quantum number n, show similar chemical properties.

Accepted Answer

Elements with the same number of valence electrons (not necessarily the same principal quantum number n) show similar chemical properties because it is the valence electrons that determine an element's chemical behavior.

Question 5

Describe how the ionization energies of main group elements vary across a period in the periodic table, using a diagram if necessary.

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Question 6

Briefly describe how the atomic radii and ionization energies of group 1A(1) elements compare with those of group 8A(18). Also, explain why the values of these properties are so different between these two groups.

Accepted Answer

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Question 7

Elements in the same period of the periodic table have similar valence shell electron configurations.

Accepted Answer

Elements in the same period of the periodic table have the same principal energy level for their valence electrons but differ in the number of valence electrons, leading to different electron configurations.

Question 8

Write down the full electron configuration for ground state atoms of
a. element number 12.
b. element number 23.
c. element number 32.

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Question 9

Atomic size decreases across a period due to an increase in the effective nuclear charge, Z_eff.

Accepted Answer

The effective nuclear charge increases across a period because the number of protons in the nucleus increases, while the number of shielding electrons remains the same. This stronger attraction between the nucleus and the valence electrons causes the atomic radius to decrease across a period.

Question 10

In Mendeleev's version of the periodic table, the elements were arranged in order of increasing atomic number.

Accepted Answer

Mendeleev arranged elements in order of increasing atomic mass, rather than atomic number. The modern periodic table is arranged in order of increasing atomic number.

Question 11

Bigger atoms generally have smaller ionization energies.

Accepted Answer

Larger atoms have electrons further from the nucleus, making them easier to remove and thus having smaller ionization energies.

Question 12

State Hund's rule, and show how it applies to the ground state of phosphorus atoms.

Accepted Answer

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Question 13

Write down the full electron configuration for ground state atoms of
a. S (element 16).
b. Pd (element 46).

Accepted Answer

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Question 14

Moseley's measurements of nuclear charges of the elements provided the basis for arranging the elements of the periodic table in order of increasing atomic number.

Accepted Answer

This is a well-known fact in the history of the periodic table. Moseley's discovery of the relationship between atomic number and nuclear charge allowed for a more accurate arrangement of the elements.

Question 15

The maximum number of electrons in an atom with the same value of n is 2n².

Accepted Answer

This is the statement of Aufbau principle which states that the maximum number of electrons in an atom with the same value of n is 2n^2. The rest of the notation (²) is not relevant to this principle.

Question 16

According to the exclusion principle, two is the maximum number of electrons in an atom which can share the same four quantum numbers.

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Question 17

Define what is meant by ionization energy, and write a balanced chemical equation to represent the relevant process for element X.

Accepted Answer

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Question 18

First ionization energies of neutral atoms may be positive or negative.

Accepted Answer

The first ionization energy of a neutral atom is always positive because energy is required to remove an electron from the atom. It is not possible for the first ionization energy to be negative.

Question 19

Describe how the atomic radii of main group elements vary with position in the periodic table.

Accepted Answer

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Question 20

The difference in energies between the 1s and 2s orbitals is due to the penetration effect.

Accepted Answer

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Quiz 8: Electron Configuration and Chemical Periodicity