Connecting Atoms
Overview
Handouts and Worksheets
for Chapters 4,5,6
• ‘The Chemical Investigator’ 12 – 20
• Naming ionic compounds practice
worksheet
• Lots of ionic naming practice problems
• Mixed Ionic/Covalent compound naming
• More naming practice
• Review sheet – molar mass and naming
• Review – naming ionic compounds
Introducing Chemical Bonds
• Many crystals of minerals and gemstones
consist of ionic compounds in which metal
and non-metal atoms are joined by ionic
bonding.
• All forces of attraction leading to chemical
bonding between atoms are electrical in
nature.
Introducing Chemical Bonds
• The electron structure of the atoms helps to
understand how the atoms bonds and the
characteristics of properties of the
substances that are formed.
• Most spontaneous changes in nature occur
to reach a more stable state. Free atoms are
seldom found in nature because atoms
undergo changes in structure to become
more stable. (Bonding)
Introducing Chemical Bonds
• Sometimes atoms bond with atoms of the
same kind (eg hydrogen gas H2) and
sometimes atoms of a different kind (eg
hydrochloric acid HCl)
• Only noble gases may exist as free atoms.
This behaviour can be explained by an
atom’s electron configuration.
Electron configuration and
Stability
• Which group on the periodic table is most
stable? Why?
• Atoms of other elements become more
stable by gaining or losing electrons to
achieve a complete outer shell configuration
Electron configuration and
Stability
• Atoms can become more stable in one of
three ways
– By giving electrons to another atom
– By taking electrons from another atom
– By sharing electrons with another atom
Types of Chemical Bond
• When atoms combine to achieve more
stable structures, three types of bonding are
possible
– Ionic Bond – results when metallic atoms
combine with non-metallic atoms to form and
ionic lattice
– Metallic Bond – results when metallic atoms
combine to form a metallic lattice
– Covalent Bond – results when non-metallic
atoms combine to form either molecules or
covalent lattices.
From Atoms to Ions
• Atoms that gain or lose electrons to achieve
a more stable outer shell configuration are
called ions.
• When an atom becomes an ion it is no
longer neutrally charged since the number
of electrons is not equal to the number of
protons.
From Atoms to Ions
• An atom that has lost electrons becomes
positively charged and is called a cation
• (eg Na+ Sodium ion)
• An atom that gains an electron becomes
negatively charged and is called an anion
• (eg Cl- Chloride)
From Atoms to Ions
• Whether an atom gains or loses electrons to
achieve stability depends on its
electronegativity (its electron attracting
power)
• When an atom gains or loses an electron it
becomes charged
• Electrovalency is the charge on an ion
From Atoms to Ions
Metallic elements
The metallic elements are those on the left hand side of the staircase.
These elements generally have low electronegativities.
They will lose electrons to achieve a noble gas configuration in their
outer shells.
aqueous
Metals in columns
NonMetals in
1, 2, 3 are electron
columns 5, 6, 7
donors.
receive Electrons.
From Atoms to Ions
Metallic elements lose an electron to form cations
• Eg
– The Li atom has
• + + + 3 protons
• - - - 3 electrons
• = neutral charge
• The Li+ ion has
• + + + 3 protons
• - - 2 electrons
= one proton
unmatched
= 1 + charge
From Atoms to Ions
• The group 2 and 13 metals contain two and
three valence electrons respectively. They
lose their outer shell electrons to form ions
with charges of 2+ and 3+ respectively.
• Note – in naming a metallic ion we use the
full name of the metal, followed the word
‘ion’ to distinguish it from the uncharged
metal.
From Atoms to Ions
Non metallic elements
• Non metallic elements are shown on the right hand side of
the staircase. These elements generally have high
electronegativity. They will gain electrons to achieve a
noble gas configuration of eight electrons in their outer
shells (with the exception of hydrogen)
Metals in columns
NonMetals in
1, 2, 3 are electron
columns 5, 6, 7
donors.
receive Electrons.
From Atoms to Ions
Non metallic elements gain an electron to form anions
Eg
The O atom has
+ + + + + + + + 8 protons
- - - - - - - - 8 electrons
The O2- ion has
++++++++
8 protons
- - - - - - - - - - 10 electrons
= 2 electrons unmatched
= neutral charge
= 2- charge
From Atoms to Ions
Non metallic elements
• It is convention in chemistry to indicate the
ions of non-metallic elements with the
suffix – ide.
• Hence in the previous example the oxygen
atom has become an oxide ion.
• Work through the Sample Problem on page
72
Review
• Complete the revision questions page 72 (1
– 4)