What is an Atom?
An Atom
Atoms are the smallest units of matter that have all the
characteristics of an element
•Protons
•Neutrons
•Electrons
•Shell
Protons, Neutrons and Electrons
Atomic Number & Mass Number
Number of neutrons = mass
number – atomic number
The Periodic Table of Elements
Drawing a Carbon Atom
No. of Protons?
6
No. of Neutrons? 12-6
No. of Electrons?
=6
6
Electron Configuration?
2, 4
Drawing an Argon Atom
No. of Protons?
18
No. of Neutrons? 40-18
No. of Electrons?
= 22
18
Electron Configuration?
2, 8, 8
Which Lithium
Atom is this?
What Atom is this?
3
2
1
Dmitri Mendeleev
The Periodic Table is an arrangement of elements in
order of increasing atomic number
Columns (Groups/Families) have similar properties
Isotopes of carbon
Isotopes are atoms which have the
same atomic number but different
mass number
Molecules are atoms that are chemically combined
or bonded
Elements
Compounds
An ion is a charged atom – i.e. an
atom which has lost or gained
electrons
• If an atom loses an
electron then it
becomes a positive
ion.
• If an atom gains an
electron then it
becomes a negative
ion.
Valency
Valency
2 Types of Bonds
Covalent
Ionic
A Hydrogen Molecule (H2)
This is an example of a Covalent Bond
where electrons are shared
A Covalent Bond
H2
A covalent bond is a bond formed by
different atoms sharing electrons in order
to have a complete outer shell
A Water Molecule (H2O)
This is an example of a Covalent Bond
where electrons are shared
A Water Molecule Covalent Bond
H 2O
Table Salt (NaCl) is an example of an
Ionic Bond
Table Salt (NaCl) is an example of an
Ionic Bond
In an Ionic Bond electrons are given and received
An Ionic Bond
Na+Cl-
An ionic bond is a bond formed by
the force of attraction between two
oppositely charged ions
Ionic Compounds
Covalent Compounds
Usually solid at room
temperature
High melting and boiling
points
Soluble in water
Usually liquid or gas at room
temperature
Low melting points
Conducts electricity
Do not conduct electricity
Undergo fast reactions
Undergo slow reactions
Insoluble in water
Chemical Equations