Ionization Energy and Periodic Trends

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Which characteristic determines the block (S, P, D) an element belongs to in the periodic table?

• The number of valence electrons.

• The type of subshell where the outermost electrons are found.

• The total number of electron shells.

• The element's atomic mass.

Answer explanation

The type of subshell where the outermost electrons are found determines the block of an element in the periodic table. Elements in the S block have their outermost electrons in s subshells, P in p subshells, and D in d subshells.

What is the general trend for atomic radius as you move from left to right across Period 3 of the periodic table?

• It increases due to more electron shells.

• It decreases because the nuclear charge increases, pulling electrons closer.

• It remains constant as the number of electron shells is the same.

• It fluctuates unpredictably.

Answer explanation

As you move from left to right across Period 3, the atomic radius decreases. This is due to an increase in nuclear charge, which pulls the electrons closer to the nucleus, resulting in a smaller atomic size.

Considering elements in the same period, which factor primarily causes the change in atomic radius across that period?

• Increased electron shielding by inner electrons.

• Decreased nuclear charge.

• Increased electrostatic attraction between the nucleus and outer electrons.

• Increased number of inner electron shells.

Answer explanation

As you move across a period, the nuclear charge increases while the number of inner electron shells remains constant. This leads to increased electrostatic attraction between the nucleus and outer electrons, resulting in a smaller atomic radius.

What is the trend for electronegativity across a period, and what is the primary reason for this trend?

• It decreases because atomic radius increases.

• It increases because the nuclear charge increases and atomic radius decreases, leading to stronger attraction for bonding electrons.

• It remains constant because the number of valence electrons changes.

• It decreases due to increased electron shielding.

Answer explanation

Electronegativity increases across a period due to the increase in nuclear charge and decrease in atomic radius, which enhances the attraction for bonding electrons, making the correct choice the second option.

What is the general trend of electronegativity across a period in the periodic table?

• It increases

• It decreases

• It remains constant

• It varies unpredictably

Answer explanation

Electronegativity generally increases across a period in the periodic table due to increasing nuclear charge, which attracts electrons more strongly. This trend explains why the correct answer is 'It increases'.

What is the definition of ionization energy?

• The energy released when an electron is added to a gaseous atom.

• The energy required to remove a mole of electrons from a mole of gaseous atoms.

• The energy required to break a covalent bond.

• The energy released during the formation of an ionic bond.

Answer explanation

Ionization energy is defined as the energy required to remove a mole of electrons from a mole of gaseous atoms, making the second answer choice correct.

Which of the following factors contributes to the increase in electronegativity as you move up a group in the periodic table?

• Larger atomic size

• Nucleus further from bonding electrons

• Stronger shielding effect

• Stronger attraction between the nucleus and bonding electrons

Answer explanation

As you move up a group, the atomic size decreases, leading to a stronger attraction between the nucleus and bonding electrons. This increased attraction enhances electronegativity, making the correct choice 'Stronger attraction between the nucleus and bonding electrons'.

Why does the first ionization energy generally decrease from Magnesium (Mg) to Aluminum (Al) in Period 3?

• Aluminum has a larger atomic radius than Magnesium.

• Magnesium has a higher nuclear charge than Aluminum.

• The electron removed from Aluminum is in a p sub-shell, which is at a higher energy level and further from the nucleus than the s sub-shell electron removed from Magnesium.

• The electron removed from Magnesium experiences greater electron-electron repulsion.

Answer explanation

The first ionization energy decreases from Mg to Al because the electron removed from Al is in a higher energy p sub-shell, which is further from the nucleus compared to the s sub-shell electron removed from Mg, making it easier to remove.

Why is the first ionization energy of Aluminium lower than that of Magnesium?

• Aluminium has a larger atomic radius than Magnesium.

• The electron removed from Aluminium is in a p-subshell, which is at a higher energy level than the s-subshell electron removed from Magnesium.

• Aluminium has more protons than Magnesium, leading to stronger nuclear attraction.

• Magnesium has a more stable electron configuration due to its filled 3s subshell.

Answer explanation

The first ionization energy of Aluminium is lower because the electron removed is from a p-subshell, which is at a higher energy level than the s-subshell electron removed from Magnesium, making it easier to remove.