Introduction to Chemical Bonding
Name/Number:______________________________
Why form Chemical Bonds?
Atoms seldom exist as independent particles in nature. The carbon dioxide you exhale,
the salt you put on your popcorn, nearly every other substance around you are made of combinations of atoms that are
held together by chemical bonds. A chemical bond is a force that holds two atoms together. In nature, the noble gases’
atoms do exist independently in nature. That is, in the balloons at a party, the helium sample is filled with individual
helium atoms moving around; none of the helium atoms are in a chemical bond with another. Why is this the case?
1. Write the electron configurations for neon and argon.
2. What do you notice about the s and p orbitals on the highest energy level?
3. What is a valence electron?
4. How many valence electrons do the noble gases [excluding helium] have?
5. Draw the electron-dot structures for neon, argon, krypton, and xenon.
6. What do the four electron-dot structures from question 5 have in common?
7. What is it about the noble gases that make them able to exist independently in nature?
Octet Rule
Elements that are not noble gases want to have the same number of valence electrons – in effect they
want to be just like the noble gases. This is known as the octet rule. The octet rule states that “chemical compounds
tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest energy
level.” By fulfilling the octet rule, each atom gains stability. Remember that the noble gases have a stable electron
configuration; this stable arrangement consists of a full outer energy level [s and p orbitals] and has lower potential
energy than other electron arrangements.
8. Which orbital types do the atoms want to have filled on their outermost energy level?
9. What three options do non-noble gas elements have to fulfill the octet rule?
10. Draw the orbital notation for sodium.
11. Remove the electron from the 3s orbital, showing that sodium lost the electron. How many protons does the
sodium atom have? After removing the electron, how many electrons does it now have? Is the atom neutral
anymore? What overall charge does sodium have?
12. What element does sodium have a configuration like now? Does this make sodium stable?
13. Draw the orbital notation for fluorine.
14. What can fluorine do to fill up the 2p orbital?
15. If fluorine gains the one electron from sodium, what charge will that fluorine atom have?
16. What element will fluorine be like after gaining that one electron?
____Check your answers with your teacher.
Types of Bonds For compounds, there are two major categories of bonds that exist – covalent and ionic. Knowing what
type of bond exists between the atoms in the compound will be incredibly important as we start naming compounds
and writing chemical formulas. Covalent bonds result from the sharing of valence electrons. Ionic bonds result from
transferring electrons between two atoms, which cause an attraction between oppositely charged particles.
17. Think about the sodium and fluorine atoms from the above section. If sodium gives the one electron that was
removed to fluorine, what type of bond will exist between the two atoms?
Bonding between atoms of different elements is rarely purely ionic or purely covalent. It usually falls somewhere
between these two extremes depending on how strongly the atoms of each element attract electrons. The degree to
which a compound is ionic or covalent can be estimated by calculating the difference in the elements’ electronegativity
values. Electronegativity is the ability of an atom in a compound to attract electrons. Below is a table that lists
electronegativity values for elements:
Using Electronegativity values If the difference in electronegativity is greater than 1.7, the bond is considered ionic. If
the difference in electronegativity values is 1.7 or less, it is classified as a covalent bond. Within covalent bonding there
are two types of bonds – nonpolar-covalent and polar-covalent. Nonpolar-covalent bonds occur when the electrons in
the bond are shared equally between the two atoms; these occur if the electronegativity difference between the two
elements is between 0.0 and 0.3. Polar-covalent bonds occur when the electrons are shared unequally between the
two atoms; these occur if the electronegativity difference between the two elements is between 0.3 and 1.7. This
difference in electronegativity values is how we classify the type of bond between two elements.
18. Define a polar-covalent bond.
19. Complete the following table.
Elements in the Bond
Electronegativity
Value for Element 1
Electronegativity
Value for Element 2
Difference in
Electronegativity
Values
Type of Bond –
Ionic, polar-covalent
or nonpolarcovalent
hydrogen and sulfur
cesium and sulfur
sulfur and chlorine
calcium and chlorine
oxygen and chlorine
nitrogen and nitrogen
sodium and chlorine
fluorine and fluorine
____Check your answers with your instructor.
Without Electronegativity values
What if you don’t have electronegativity values handy? With your partners you
will develop a quick way to determine whether a molecule is ionic or covalent.
20. Look at your table from question 19. Write the element combinations below that you classified as ionic. You can
just write the symbols of the elements, not the names.
21. Look at the first element for each compound in question 20. Are they metals or nonmetals? Circle one.
22. Look at the second element for each compound in question 20. Are they metals or nonmetals? Circle one.
23. Look at your table from question 19. Write the element combinations below that you classified as covalent
[either polar-covalent or nonpolar-covalent]. Again, you can write just the symbols of the elements.
24. Look at the first element for each compound in question 23. Are they metals or nonmetals? Circle one.
25. Look at the second element for each compound in question 23. Are they metals or nonmetals? Circle one.
26. Using your answers to questions 21-22 and 24-25, complete statements below to create general rules.
a. If a ________________ and a ________________ combine, the bond is ionic.
b. If a ________________ and a________________ combine, the bond is covalent.
____Check your answer with your instructor and obtain your homework paper.
Introduction to Chemical Bonding Homework
1. Define ionic bond. What happens to the electrons in an ionic bond?
2. What happens to the electrons in a covalent bond?
3. Define polar-covalent bond.
4. Define nonpolar-covalent bond.
5. Use electronegativity values to classify the bond type between the following elements as either nonpolarcovalent [NPC], polar-covalent [PC], or ionic [I].
a. potassium and nitrogen
b. hydrogen and hydrogen
c. hydrogen and oxygen
d. phosphorus and chlorine
e. calcium and bromine
6. What types of elements [metals, nonmetals] tend to form ionic bond? Which types form covalent bonds?
7. Classify the bond type [either ionic or covalent] between the following elements without using
electronegativity values.
a. copper and phosphorus
b. carbon and nitrogen
c. sodium and chlorine
d. hydrogen and phosphorus
e. potassium and iodine
f.
potassium and bromine
g. aluminum and nitrogen
h. tin and sulfur