Chemistry Homework: Advanced Concepts in Atomic Structure and Bonding

This chemistry homework assignment delves into several core concepts of atomic structure and chemical bonding. The solutions begin with arguments for and against increased funding for atomic structure research, discussing the potential benefits in medical advancements like MRI technology versus the rising costs and limited accessibility of such technologies. The assignment then explores Niels Bohr's atomic model and the energy differences in electron transitions, followed by an analysis of zirconium's electronic configuration and ion stability. Further sections cover orbital overlap diagrams in ammonia, drawing Lewis structures and structural formulas for various molecules, and determining the type of hybrid orbitals in ammonia. Electronegativity differences are calculated to determine the ionic or molecular nature of compounds and their ranking based on ionic character. Electron dot diagrams and structural formulas are drawn to predict the shapes and polarities of molecules like IO3- and CHCl3. Finally, the assignment examines the bond angles in water and methane and the suitability of carbon dioxide as a solvent in dry cleaning, including its pros and cons. The assignment concludes with an explanation of the boiling point trends in halogens and the forces related to the number of electrons.

Surname 1
Name
Professor
Course
Date
Chemistry Questions
Question 1
Argument for:
More funding for atomic-structure research will allow scientists and researchers to have a
detailed understanding of how sub-atomic particles interact in different conditions and the
products of these interactions. For instance, further research on MRI will enable researchers to
discover more advanced tools and methods that can be used for noninvasive imaging of the body,
surgery and diagnosis of different health complications. The researchers will be able to
understand what exactly happens when a patient’s body absorbs radio waves emitted by an MRI
machine with precise hydrogen atom nucleus frequency and the impacts of this to the body.
Therefore the funding is essential as it will help examine the structure of atoms and use the
information to discover several tools and methods for treatment of various diseases thus saving
millions of lives worldwide.
Argument against:
Statistics show that the cost of quantum mechanics research has by skyrocketing over the years
and this is a major concern that affects funding of atomic-structure research. Unfortunately, these
are complaints that despite the large amount of money invested in MRI research, only a selected

Surname 2
few people (a particular demographic) can still have access or afford the technology for the
treatment of their health complications. Additionally, the scope and objectives of MRI research
are usually affected by new discoveries and ideas. This has left findings on the interactions of
electrons and atoms from previous studies to be observational only. It therefore means that
predictions made from these observations are less accurate especially in cases where larger and
more sophisticated systems are involved. Therefore the increasing costs of these researches, the
limited number of persons who can use the technology and the less accurate predictions made
from these researchers are making more funding in further atom-structure research of no value.
For these reasons, the funds should be put in more useful projects such as improving preventive
care and provision of essential needs for people living in underdeveloped and less developed
countries.
Question 2
According to Niels Bohr’s model of the atom, electrons emit colours found in the line spectra.
The difference in energy between these lines is attributed to electrons moving between different
levels of orbitals – from higher to comparatively lower orbitals. For the case of the line in the
visible light spectrum, an electron can be said to be moving from the fifth orbital to the second
orbital. While for the case of the line in the ultraviolet spectrum, an electron can be said to be
moving from the sixth orbital to the second orbital. This means that the electrons in each
spectrum is moving from a different origin to the same destination. As a result, the electrons
responsible for producing light in the ultraviolet spectrum emits more energy compared to those
producing light in the visible light spectrum.
Question 3

Surname 3
a) Energy-level diagram and electronic configuration
Zirconium has 5 energy levels. The energy-level diagram of zirconium is provided in the figure
below
The electronic configuration of zirconium is given as: 1s22s22p63s23p63d104s24p64d25s2
b) Why the Zr+4 ions exit
The atomic structure of zirconium contains 40 electrons. The closest inert gas to this element is
krypton, which has 36 electrons. Therefore Zr4+ ion exists because zirconium loses all the four
electrons from its outer shell so as to gain a stable electronic configuration (to become
chemically stable) similar to that of krypton. In other words, Zr4+ exists because zirconium loses
the four electrons (represented as Zr4+) so as its outer shell to become full and its electronic
configuration stabilized.
c) Stability of Zr atom and Zr ion
Zr ion is a more stable than Zr atom because the former has a completely filled valence shell.
This means that the probability of Zr ion reacting is very low, which increases its stability. The

Surname 4
electron configuration of Zr ion is the same as that of an inert gas krypton. Zr is also more stable
because it is a charged ion hence it loses four electrons so as to gain the electron configuration of
an inert gas. On the other hand, the valence shell of Zr atom (a neutral atom) is not completely
filled (it has two free valence electrons) making it more reactive thus less stable because it can
easily react by losing the two electrons so as to become stable.
Question 4
The orbital overlap diagram representing the bonding in ammonia is provided in the figure below
Question 5
Draw the Lewis structure and structural formula for HCN and SO32-
a) HCN
Lewis structure

Surname 5
Structural formula
H−C≡N
b) SO32-
Lewis structure
Structural formula
Question 6
a) Energy-level diagram
The energy-level diagram of NH3 is provided below

Surname 6
b) Type of hybrid orbitals
NH3 contains four sp3 hybrid orbitals. Out of these four, only three hybrid orbitals (bonding pair)
will take part in bonding. This is because the fourth hybrid orbital is already filled (chemically
stable – lone pair or non-bonding orbital) whereas the other three hybrid orbitals need an extra
electron so as to become stable (for their valence shell to become completely filled) hence they
have to bond or react so as to gain the extra electron and become stable like the inert gas neon.
c) Energy-level diagram of hybrid orbitals
The energy-level diagram of hybrid orbitals is provided below
Bonding with an N atom will differ with that with a C atom because N atom contains four
incomplete orbitals and five outer electrons. Three of the four incomplete orbitals of N contain
one electron each while the fourth has two electrons. Each of the 2p orbitals of N atom contains
3 electrons. On the other hand, the C atom also contains four incomplete orbitals but its 2p
orbitals have only 2 electrons and the third 2p orbitals does not have any electron. Therefore the

Surname 7
difference in the number of electrons in the 2p orbitals of these atoms makes their bonding to
differ.
Question 7
a) Difference in electronegativity
Difference in electronegativity (ΔEN) is determined by subtracting the smaller electronegativity
from the larger electronegativity of the molecule.
i) CaBr2
Ca = 1
Br2 = 2.96
ΔEN = 2.96 – 1.0 = 1.96
ii) Na3N
Na3 = 0.93
N = 3.04
ΔEN = 3.04 – 0.93 = 2.11
iii) CH4
C = 2.55
H4 = 2.20
ΔEN = 2.55 – 2.20 = 0.35
b) Ionic or molecular compound

Surname 8
A compound is ionic or molecular depending on its ΔEN. A compound in ionic when ΔEN >2
and a compound is molecular when ΔEN<2.0.
The ΔEN of CaBr2 is 1.96 (1.6 <ΔE<2.0) hence the compound is ionic since the compound
contains a metal (otherwise it would have been molecular if all the elements were non-metals).
The bond of the compound is polar covalent.
The ΔEN of Na3N is 2.11 (ΔE>2.0) hence the compound is ionic. The bond of the compound is
ionic.
The ΔEN of CH4 is 0.35 (ΔE<0.5) hence the compound is molecular. The bond of the compound
is nonpolar covalent.
c) Ranking
Ionic character is represented by the value of ΔEN. In this case, the compounds are ranked from
the one with the greatest value of ΔEN to the smallest value. The decreasing order of these
compounds in terms of their ionic character is as follows: Na3N (most ionic character), CaBr2
(medium ionic character) and CH4 (least ionic character). In this ranking order, compounds
containing metals are always found in the start of the order because they usually have higher
values of ionic character (ΔEN values).
Question 8
a) Electron dot diagram
The electron dot diagram of ion IO3 is provided below

Surname 9
The structural formula of ion IO3 is provided below
b) Predict shape
The predicted shape of the ion is trigonal pyramidal. This is because the central iodine atom of
the ion is surrounded by one lone pair and three bond pairs.
c) Polar or non-polar?
The ion is a polar molecule because it contains a lone pair and polar bonds. This means that the
distribution of its electrons are unequal, i.e., the electrons are not equally shared hence the bond
dipoles are not able to cancel out each other. The bonding oxygen electron pairs are repelled
downwards by the iodine lone pair to give the pyramidal shape. Thus the end of oxygen is
slightly negative while that of iodine is slightly positive.
Also, ΔEN values can be used as follows

Surname 10
I = 2.66
O = 3.44
ΔEN = 3.44 – 2.66 = 0.78
Since 0.5<ΔEN<1.6, the bond of the ion is polar covalent.
Question 9
a) Electron dot diagram
The electron dot diagram of molecule CHCl3 is provided below
The structural formula of molecule CHCl3 is provided below
b) Predict shape

Surname 11
The predicted shape of the molecule is tetrahedral. This is because the central carbon atom of the
molecule is surrounded by four bond pairs but does not have any lone pair.
c) Polar or non-polar?
The molecule is a polar because it contains unequal poles. The dipoles of the molecule do not
cancel out each other. The hydrogen side of the molecule is more positive than the carbon side
while the chlorine sides of the molecule are more negative than the carbon side. Therefore the
unequal poles of the molecule make it polar.
Question 10
The bond angles in water and methane molecules are not identical because these molecules
experience different degrees of repulsion dictated by the type of orbitals they have. All the
orbitals of methane are bonding orbitals (4 bonding pairs and zero lone pairs) that exhibit equal
magnitude of repulsion, giving tetrahedral angle. On the other hand, water contains 2 lone pair
orbitals and 2 bonding pairs. The lone pair orbitals have a greater repulsion that pushes the non-
bonding orbitals far from each other causing them to remain nearer to the central atom. This
causes the bonding orbitals to move closer to each other thus lowering the bond angle.
Question 11
a) Suitability of carbon dioxide
Carbon dioxide is a suitable solvent for use in dry cleaning because it is a non-polar molecule.
This implies that the distribution of bond dipoles around carbon dioxide molecule’s central atom
is symmetrical hence they cancel out and produce a molecule that does not have a net molecular
dipole. The main stains (including grease, fat and oil) are made of non-polar molecules hence

Surname 12
they can easily dissolve in liquid carbon dioxide. Therefore carbon dioxide is a suitable solvent
for use in cleaning because it will easily dissolve and remove different stains from the fabric
using its polar covalent bonds.
b) Pros and cons
Pros
The pros of using liquid carbon dioxide for dry cleaning include: it is non-toxic and does not
produce hazardous waste hence its use does not have harmful health or environmental problems,
and it is faster (reduces cleaning time by almost half) and more effective in eliminating non-polar
stains (such as oil, fat and grease) from the fabric because liquid carbon dioxide has a low
viscosity and is a non-polar solvent.
Cons
The cons of using liquid carbon dioxide for dry cleaning include: it has limited ability to dissolve
and remove polar molecules (such as grass and chocolate stains), and its use requires complex
airlock systems that increases the overall material cost of the dry cleaning process.
Question 12
a) Boiling point
The boiling point of halogens increases with the increase in the number of electrons (atomic
number) of the halogens. Halogens with less number of electrons are lighter and are more
electronegative thus they have a lower boiling point compared to halogens with more number of
electrons, which are heavier and less electronegative thus they have a higher boiling point. The
halogens are diatomic molecules whose intermolecular forces increase down the group (with the