Topic 1 - Matter and Energy - Revsworld

Topic 4 – Chemical .
Bonding
Topic outline
In this topic, you will learn the following concepts:
. Chemical bonds and stability of atoms . Molecular substances and molecular polarity
. Chemical bonding and energy . Intermolecular forces
.Types of chemical bond between atoms
Introduction
. Types of substances and their properties
1. Chemical bonding and stability: How and why atoms bond
Atoms bond so they can attain a full valance shell and become stable.
Octet of electrons is when an atom has a full valance (outermost) shell with 8 electrons
NOTE: Not every atom needs eight (8) valance electrons to be stable.
An atom can get a full and stable valance shell configuration by :
A) Transferring or Accepting electrons (ionic bonding)
or
B) Sharing electrons (covalent bonding)
RECALL that noble gas atoms have full valance shell configurations and they are very stable.
. The electron configuration of a bonded atom is similar to that of the nearest noble gas (Group 18) atom
. Therefore, an atom is more stable when it is bonded to other atoms than when it is by itself
2. Chemical bonding and atom stability: Determining the Noble gas atom a bonded atom resembles
Concept Task: Be able to determine which noble
gas element an atom (or atoms) in
a bond resembles.
To determine which element a bonded atom
Lesson 1: Chemical bonding Stability of atoms
bonds
Chemical bonding is the simultaneous attraction of two positive nuclei to negative electrons.
Chemical bonding is said to be the “glue” that holds particles (atoms, ions, molecules) together in
matter.
When atoms bond they become much more stable than when they are in their free states. Since most
atoms do not have a full valance shell, they are unstable. In other for these atoms to attain a full valance
shell and be stable, they must bond with other atoms.
In this lesson, you will learn how and why atoms bond.
resembles
Locate the element in question on the Table
and note its atomic number.
Choose a Group 18 atom that is closest (in
atomic number) to the element
in the question.
. .
LOOKING Back: Topic 3- Atomic Structure
You had learn about
Configurations of ions.
Example 1
When a sulfur atom bonds with sodium atoms to
form the compound Na 2 S, the configuration of
sulfur atom is similar to which element?
1) Na 2) O 3) Ne 4) Ar
Answer: Choice 4: Because the closest noble gas to
sulfur (atomic number 16) is
Argon (atomic number 18)
Example 2
The electron configuration of Sr and H ions in the
formula SrH 2 are similar to those of elements
1) Kr and He 3) Ar and Ne
2) Rb and He 4) Ca and Li
Answer: Choice 1 . On the Periodic Table:
The closest Group 18 atom to Sr (# 38) is Kr (# 36).
The closest Group 18 atom to H (# 1) is He (# 2)
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