Chapter 5

12! Calculate the effective nuclear charge on a valence electron in a sulfur atom.

+6 (16 - 10) Sulfur has an atomic number of 16. There are 16 protons and 16 electrons in a sulfur atom. Sulfur has 6 valence electrons and 10 shielding electrons. Therefore, electrons in the valence shell will experience an effective nuclear charge of 6+.

11. Calculate the effective nuclear charge on a valence electron in a bromine atom.

+7 (35 - 28) Bromine has an atomic number of 35. There are 35 protons and 35 electrons in a bromine atom. Bromine has 7 valence electrons and 28 shielding electrons. Therefore, electrons in the valence shell will experience an effective nuclear charge of 7+.

14. The ground state electron configuration of a Se atom is:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴ (34 electrons) The element Se is a main-group element on the right-hand side of the periodic table (meaning it is in the p block) and the fourth row, so its electron configuration will end with 4p. The electron configuration of Se is 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴.

16. Which of the following is the electron configuration of a neutral Fe atom?

1s²2s²2p⁶3s²3p⁶4s²3d⁶ (26 electrons) The element Fe is a transition metal (meaning it is in the d block) and the fourth row; because elements in the d block have the quantum number n one less than their row in the periodic table, the electron configuration of Fe will end with 3d. The electron configuration of Fe is 1s²2s²2p⁶3s²3p⁶4s²3d⁶.

5. How many core electrons does an atom of beryllium (Be) contain?

2 Be has four electrons and an electron configuration of 1s²2s². The electrons in the 1st shell are in the core and the electrons in the outer shell are valence electrons.

1. For which atomic orbital does n = 3 and ℓ = 1?

3p Atomic orbitals are described by their principal quantum number (n) followed by a letter that corresponds to the value for the angular momentum quantum number (ℓ). Here, n = 3, so the atomic orbital symbol will begin with 3. The quantum number ℓ = 1 (s = 0, p = 1, d = 2, f = 3), which corresponds to p. Therefore, this is a 3p atomic orbital.

17! For an atom of carbon, which ionization will exhibit a very large increase in the energy relative to the preceding ionization?

5TH There are four valence electrons in an atom of carbon. The 5th ionization will require a very large increase in the energy relative to the preceding ionization.

10. Which of the following pairs of ions represent isoelectronic species?

Al³⁺ and O²⁻ (10 electrons) Isoelectronic species are elements/ions with the same electron configuration (and therefore the same number of electrons). Of the options given, the species Al³⁺ and O²⁻ both have the electron configuration of Ne (1s²2s²2p⁶), meaning they are isoelectronic.

9. The energy released in the reaction F(g) + e⁻ → F⁻(g) is known as the:

ELECTRON AFFINITY The electron affinity is the change in energy when an electron is added to a neutral gaseous atom to form an ion.

15. Which element has the electron configuration 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p²?

Ge (32 electrons) This electron configuration ends with 4p, meaning it is an element in the p block (a main group element on the right-hand side of the periodic table) in the fourth row. The 2 in 4p² indicates that it is the second element in this row, so the element must be Ge.

13! Which of the following radii comparisons is correct?

In³⁺ < In⁺ Cations are always smaller than the neutral atom from which it is derived. Anions are always larger than the neutral atom from which it is derived. Therefore, the smaller ion in a pair will be the one with fewer electrons.

3. What is the noble gas core in the electron configuration for Ru?

Kr The noble gas core for a given element is the last noble gas filled in the periodic table prior to the given element. Here, the last noble gas prior to Ru is Kr, so that is its noble gas core.

7. All of these are factors that affect the effective nuclear charge, Zeff, EXCEPT:

MASS NUMBER The Zeff is affected by the type of orbital an electron occupies, the number of core electrons, and the number of valence electrons.

6. Which of the following atom(s) below has/have five valence electrons?

N Elements in Group 15 have 5 valence electrons. These include: N, P, As, Sb, Bi, and Mc.

8. Rank the following atoms in order of increasing size (i.e., smallest to largest): Li, Al, Be, Ba, O.

O < Be < Li < Al < Ba In general, atomic radius decreases across a period and increases down a group.

2. True or false: two electrons can simultaneously occupy the same (n,ℓ,mℓ) orbital.

TRUE The Pauli exclusion principle states that no two electrons in a given atom can share the same set of four quantum numbers (n, ℓ, mℓ, ms). Two electrons may share the first three quantum numbers (n, ℓ, mℓ) as long as their ms (spin) quantum numbers are not the same, so this statement is true.