b Formula of different Molecules Specific Aim To appreciate the idea of Formula and its Significance to appreciate the rules followed in writing the Formula of a Molecule to become familiar with the formulae of different ID: 920048
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Slide1
Introduction
Teaching Points: (a) Definition of Formula
(
b)
Formula of different Molecules
Specific Aim
: To appreciate the idea of Formula and its Significance, to appreciate the rules followed
in
writing the Formula of a Molecule, to become familiar with the formulae of different
Molecules
.
Slide2Questions & Answers
Question
:
Give the definition of Symbol.
Answer
:
The short form used to refer to an element is called a Symbol.
Question
:
How the symbol for an Element is written?
Answer
:
Each Element is represented by the first letter of its name written in capitals.
e.g. Hydrogen is written as H, Oxygen is written as O etc.
If two elements have names beginning with the same letter, then a second letter in lowercase is
written
with the first letter of the name.
e.g. Calcium is written as
“
Ca
”,
Chlorine is written as
‘
Cl
’
etc.
Slide3Questions & Answers
Question
:
Give the Symbols of
Aluminium
, Gold, Mercury, Sodium, Zinc.
Answer:(Student)
Aluminium
-Al, Gold-Au, Mercury-Hg, Sodium- Na, Zinc-Zn.
Question
:
What is the Short form of a molecule of an Element or Compound is called?
Answer:
Formula
Question
:
Are there any rules to be followed in writing the short form of a molecule of an Element or Compound?
Answer:
Yes, There are some rules--
Slide4Introduction
You know cadets;
Like Symbols, we have short form of a molecule of an Element or Compound.
In writing the short form of a molecule of an Element or Compound, we have to follow certain rules.
Today, we shall discuss about Formulae, the rules to be followed and examples.
Slide5Formulae:
Formulae:
The short form of a molecule is known as its formula (Plural: Formulae
).
Note:
Molecules
are represented by a combination of symbols and numbers.
Each molecule of an Element or a Compound has its formula.
The atoms in a molecule are held together by strong forces of attraction called Chemical Bonds
.
Rules:
Formula of a molecule of an Element is represented by its symbol, with a number beside it representing how many atoms are involved in the formation of the
molecule
e.g
. Molecular formula of Oxygen is written as O
2
. Two atoms of Oxygen are involved in the formation of one molecule of Oxygen
.
Formula of a molecule of a Compound is represented by the symbols of its constituent Elements, the number representing the contribution from each of the Element’s atoms is written beside the respective symbols.
e.g
. A molecule of Water is made up of two atoms of Hydrogen and one atom of Oxygen. So, the formula for one molecule of Water is H
2
O.
Slide6Formulae of some compounds:
Formulae of some compounds:
Compound
Formulae
Compound
Formulae
Oxygen
O
2
Carbon-di-Oxide
CO
2
Chlorine
Cl
2
Water
H
2
O
Nitrogen
N
2
Nitrogen-di-Oxide
NO
2
Sodium Chloride
NaCl
Nitrogen-Tri-Oxide
NO
3
Hydrogen Chloride
HCl
Sulphuric Acid
H
2
SO
4
Carbon Mono-Oxide
CO
Nitric Acid
HNO
3
Slide7Some Questions & Answers
Question
:
What is Formula?
Answer
:
The short form of a molecule is known as its formula (Plural: Formulae).
Question
:
What are the rules to be followed in writing the formula of a molecule?
Answer
:
Formula of a molecule of an Element is represented by its symbol, with a number beside it representing how many atoms are involved in the formation of the molecule.
e.g. Molecular formula of Oxygen is written as O
2
. Two atoms of Oxygen are involved in the formation of one molecule of Oxygen
.
Formula of a molecule of a Compound is represented by the symbols of its constituent Elements, the number representing the contribution from each of the Element’s atoms is written beside the respective symbols.
e.g
. A molecule of Water is made up of two atoms of Hydrogen and one atom of Oxygen. So, the formula for one molecule of Water is H
2
O.
Slide8Some Questions & Answers
Question
:
Give the formulae for
Sulphuric
acid and Nitric acid.
Answer:(Student)
Sulphuric
Acid- H
2
SO
4
, Nitric acid- HNO
3
Question
:
What is a Chemical Bond?
Answer
:
The
atoms in a molecule are held together by strong forces of attraction called Chemical Bonds.
Slide9Question?
Question
:
Give one examples each of molecules that are made up of (
i
) three atoms (ii) five atoms (iii) seven atoms
Answer
:
Three atoms: CO
2
(Carbon-di-Oxide)
Five atoms: HNO
3
( Nitric Acid)
Seven atoms:
H
2
SO
4
(
Sulphuric
Acid)