Chapter 1: Chemical Bonding
Answers to the Questions relating to Atoms, Orbitals and Electron Configurations:

Atoms:

1.  How many electrons are there in N3-?
           N has 7 electrons so N3- has 7+3 = 10, 8 valence and 2 core

2.  What is the atomic mass unit for an atom of bromine?
           79.904 amu, this is a weighted average of the isotopic masses for 79Br and 81Br.

3.  How many protons and neutons are there is each of the following : 1H, 2H, 12C, 16O, 35Cl and 37Cl ?

The atomic number, Z, which defines the number of protons is defined by the elemental symbol. The mass numbers are given as superscripts before the atomic symbol. Note that because atoms are neutral, the number of positive protons also defines the number of negative electrons surrounding the nucleus.
Element
Atomic number
Mass number
Protons
Neutrons
1H
1
1
1
0
2H
1
2
1
1
12C
6
12
6
6
16O
8
16
8
8
35Cl
17
35
17
18
37Cl
17
37
17
20

Orbtials:

1.   Which quantum number defines an orbitals energy level ?

The principle quantum number, n, defines the energy level.
2.   What are the quantum numbers that describe a 3p orbital?

           First determine what quantum numbers are indicated by the name 3p.

            Any of the following 'sets' of quantum numbers will be valid:
 
 n
l
ml
3
1
1
3
1
0
3
1
-1
3.  How many occupied valence orbitals are there in Cl and I?
First consider their electron configurations (core, valence)


Both have a total of four, occupied, valence orbitals, one s orbital and three p orbitals.

4.  What are the quantum numbers for an electron in a 3s orbital?
First determine what quantum numbers are indicated by the name 3s.

Then note that you want the quantum numbers for an electron so ms must also be considered!
Any of the following 'sets' of quantum numbers are valid.

 
n
l
ml
ms
3
0
0
-1/2
3
0
0
+1/2
Electron Configurations:

Use the information given in the box below when answering the next three questions:
 

(a)  [Ar] (d)  1s22s22p63s23px23py1
(b)  1s22s22p63s1 (e)  1s22s22p63s23px13py13pz1
(c)  1s22s22p63s1  

1.  Which of the electron configurations above best describes the ground state electron configuration of Cl-? (a)
2.  Which of the electron configurations above is possible for the ground state of P?  (e)
3.  Which of the electron configurations above describes an excited state of Mg+? (c)

4.  Is the following electron configuration consistent with Hund's rule of maximum multiplicity?

Yes, all electrons unpaired before pairing

 5.  Is the following electron configuration consistent with Pauli's exclusion principle?

No, two electrons in a p orbital have the same four quantum numbers

 6.  What is the orbital energy diagram that best describes the core electron configuration of Si ?

Did you draw the core or did you draw the valence electron configuration by mistake ?
7.  What is the orbital energy diagram that best describes the valence electron configuration of O ?

Did you draw the valence or did you draw the core electron configuration by mistake ?