Ch 7: Electron Configuration and the Periodic Table

Question 1

The nuclear charge (Z) is simply the number of…

Answer 1

….protons in the nucleus of an atom.

p. 290

Question 2

Effective nuclear charge (Z_eff) is the actual ________ __ ______ ______ that is “experienced” by an electron in the atom. The phenomenon of shielding happens when a many-electron atom is partially shielded from the positive charge of the nucleus by the other electrons in the atom.

Answer 2

magnitude of positive charge

Question 3

Within an isoelectronic series, the higher the effective nuclear charge, the _______ the ionic radius.

Answer 3

smaller

Question 4

K has a lower IE₁than Ca, but Ca has a lowerIE₂ than K because:

Answer 4

IE₁increases from left to right across a period. However, because K has only one valence electron,IE₂ for K involves the removal of a core electron − requiring significantly more energy.

Question 5

Looking at a periodic table, rank the following elements in order of decreasing ionization energy.

C, Mg, Si, O, Ca

Answer 5

O > C > Si > Mg > Ca

Question 6

Electron affinity is the energy released (the negative of the enthalpy change ΔH) when an atom in the gas phase _______ __ ______.

Answer 6

accepts an electron

p. 295

Question 7

Like ionization energy, electron affinity…

Answer 7

….increases from left to right across a period.

p. 295

Question 8

What is the equation which represent the electron affinity of S^- ?

Answer 8

S^- (g) + e^- → S^2- (g)

Question 9

What is trend in first ionization energy across the periodic table?

Answer 9

Ionization increases as you move up the periodic table, and also increases as you move from left to right. This is the same trend as electronegativity.

Question 10

Arrange the following in order of increasing first ionization energy:

F, K, P, Ca, Ne

Answer 10

K < Ca < P < F < Ne

Question 11

In spite of the known trend for first ionization energy across the periodic table, aluminum has a lower first ionization energy than magnesium. Why is this?

Answer 11

The group 3A elements, such as aluminum, all have a single electron in the outer most p subshell, which is well shielded from the nuclear charge by the inner electrons and the ns² electrons. Therefore, less energy is needed to remove a single p electron than to remove a paired s electron from the same principal energy level (such as for magnesium).

Question 12

Which of the following would you expect to have the highest electron affinity?

He, K, Co, S, Cl

Answer 12

Cl