Chem100/11 Assignment 6 Solutions 2012/2013

Due to March 25

Electronic Structure of Atoms. Periodic properties of the Elements (Chapters 6 and 7)

1. {5}

(a) What is the wave length (in nm) of radiation that has frequency of 6.1 x 10¹⁴ s^-1 ? (c= 3.00 x10⁸ m/s) (hint: sample exercise 6.2)

(b) what part of the electromagnetic spectrum this radiation belongs to? (for example, X rays, Infrared, etc. Hint: chapter 6.1 in the text)

(a) λ = c/ ν = 3.00 x 10⁸ms^-1 /6.1 x 10¹⁴ s^-1 = 4.91 x 10^-7 m = 491 x 10^-9 m = 491 nm

(b) visible (blue)

2. {10}

a) there are __1___ orbitals in the first electron shell

b) there are __4___ orbitals in the second electron shell

c) there are maximum ___6__ electrons in the p-subshell

d) there are maximum ___14__ electrons in the f-subshell

e) the principle quantum number for the first d subshell is __3___

f) Each d-subshell can accommodate maximum __10____ electrons

g) A p_z orbital is degenerate with ____2_(p_y, p_x)_ orbitals in a many-electron atom

h) the 2p subshell in a ground state of atomic nitrogen contains __3___ electrons

i) there is/are ___2___ unpaired electrons in oxygen atom

j) [Ar] 3d²4s² is the electron configuration of a(n)__Ti ___ atom

3. {5}

Which of the following sets of four quantum numbers (n, l, m_l, m_s) are valid and which are not?

a) 2, 1, 0, 1 not valid

b) 2, 1, 0, -1/3 not valid

c) 3, 2, 0, ½ valid

d) 2, 1, 0, +1/2 valid

e) 2, 1, 2, -1/2 not valid

4. {10} For each atom/ion, write down the number of valence electrons and unpaired electrons in the ground state

a) (2) hydrogen 1,1

b) (2) carbon 4, 2

c) (2) nitrogen 5, 3

d) (2) fluorine 7, 1

e) (2) Fe²⁺ 6, 4

5. {5} Using the periodic table, write down the condensed ground state electronic configurations for Cl, Co⁺, Na, Br^- , and C.

Cl: [Ne]3s²3p⁵; Co⁺: [Ar] 3d⁷4s¹; Na: [Ne] 3s¹; Br^- : [Ar] 3d¹⁰4s²4p⁶= [Kr]; C: [He]2s²2p²

6. {5} Write down the condensed ground state electronic configurations for V and Cr and Ni and Cu. Briefly explain the singularities.

V [Ar] 3d³4s², Cr [Ar] 3d⁵4s¹ Cr has half-occupied d-subshell which is exceptionally stable

Ni [Ar]3d⁸4s², Cu [Ar] 3d¹⁰4s¹ Cu has fully-occupied d-subshell which is exceptionally stable.

7. {5} write down the following elements in order of increasing first ionization energies (IE₁). Briefly explain the singularities in the trend (hint: section 7.9) :

Cl, P, S, Al, Si, Na, Mg

Na, Al, Mg, Si, S, P, Cl

Mg has greater IE than Al due to exceptional stability of completely filled s-subshell; P has greater IE than S due to exceptional stability of half- filled p-subshell.

8. {10} An element, X, with the highest principal quantum number n = 4, has the following ionization energies, IE:

IE1= 1000 kJ/mol; IE2= 2252kJ/mol; IE3= 3357 kJ/mol; ; IE4=4556 kJ/mol; IE5=7004 kJ/mol; IE6=8496; IE7=27107 kJ/mol.

a) {4} Identify the element

Se

b) {3} Write down balanced reaction between the element and molecular oxygen. Show physical states.

2Se (s) + 3O₂ (g) à 2SeO₃ (g) (very low stability)

c) {3} Would you expect the product of the chemical reaction of the element with O₂ to be a basic, or an acidic oxide? Write down chemical equation for the reaction between the oxide and water.

Acidic properties :

SeO₃ (g) + H₂O (l) à H₂SeO₄ (aq) (strong acid)

9. {10} Write down empirical formula for the ionic compound that best fit the following descriptions:

(a) the alkali cation with the smallest radius and an anion with the smallest radius

LiF

(b) The alkaline earth metal with the highest ionization energy that combines in a 1:2 ratio with the element from Period 3.

BeCl₂

(c) The largest element from period 5 combined with the Group 16 element with the most negative electron affinity.

Rb₂S

(d) The compound formed from the elements of Period 3 that have the largest radius and most negative electron affinity.

NaBr

10. {10} Write balanced equations for the following reactions:

(a) potassium oxide with water

K₂O (s) + H₂O (l) à 2KOH (aq)

(b) diphosphorus pentoxide with water

P₂O₅ (s) + 3H₂O (l) à 2H₃PO₄ (aq)

(c) sulfur trioxide with solution of sodium hydroxide

SO₃ (g) + 2NaOH (aq) à Na₂SO₄ (aq) + H₂O

(d) magnesium with chlorine

Mg(s) + Cl₂ (g) à MgCl₂ (s)

(e) Fe (II) oxide with diluted hydrochloric acid

FeO (s) + 2HCl (aq) à FeCl₂ (aq) + H₂O (l)

11. {5} Write down the condensed electron configuration for the following ions:

K⁺, Mg²⁺, Cr³⁺, P³⁺, P^3-, N^3-, S^2-, F^-, I⁷⁺, Cu⁺.

K⁺ [Ar] Mg²⁺ [Ne] Cr³⁺ [Ar] 3d³ P³⁺ [Ne]3s² P^3- [Ar] N^3- [Ne] S^2- [Ar] F^- [Ne] I⁷⁺ [Kr] 4d¹⁰ Cu⁺ [Ar] 3d¹⁰

12. {10} write down the most common monoatomic ions formed from the following atoms:

Li, Ca, Al, H, O, F, Cl, S, Br, N

Li⁺, Ca²⁺, Al³⁺, H⁺ (H^-), O^2-, F^-, Cl^-, S^2-, Br^-, N^3-.

13. {5} arrange the following oxides in order of increasing basicity (from the most acidic to the most basic):

SO₃, CaO, Fe₂O₃, CO₂, Na₂O, H₂O

SO₃<CO₂<H₂O<Fe₂O₃<CaO<Na₂O

14. {5} Arrange the following atoms in order of increasing radius:

K, Ge, Rb, Br, F

F<Br<Ge<K<Rb

15. {5} Arrange the following atoms in order of increasing (more negative) electron affinities ( chapter 7.5) :

Cl, F, N, O, C, Be, Li, S, H, P

Be, N, Li, P, H, C, O, S, F, Cl (from Fig. 7.11)