Transcript EXPLORING THE NATURE OF MATTER

EXPLORING THE
NATURE OF MATTER
DIVERSITY OF OBJECTS IN
NATURE
 Nature
has an unlimited variety of
living and non-living objects
UNDERSTANDING THE BASIC
CONSTITUENTS
 Scientists
have been trying from a
long
time
to
understand
the
composition of different objects.
 One
of the scientists who have made
great contribution in this direction is
-John Dalton
Dalton’s Findings
Law of Constant Proportions:
Dalton found that no matter which sample of a
particular substance was chosen, the proportion
by weight of its elementary constituents
remained the same.
e.g. Water taken from any place is composed of
Hydrogen and Oxygen. The proportion in it by
weight of hydrogen and oxygen is always 1:8.

Dalton’s Findings Contd…

Law of Multiple Proportions: Whenever two
elements combine to form more than one
compound, the different masses of one element
that combine with the same mass of the other
element are in the ratio of small whole numbers.
In Water H20, 1g of Hydrogen
combines with 8g of oxygen
In Hydrogen Peroxide H202, 1g of
Hydrogen combines with 16g of
oxygen
The ratio of oxygen combining with the same amount i.e. 1g of
hydrogen is 8:16 or 1:2 between water and hydrogen peroxide- a
small integral ratio.
Dalton Proposed the following..



All matter is made of very tiny indivisible
particles called atoms.
An element is a substance that has the same kind
of atoms in it i.e., all atoms of an element are
identical.
Atoms of an element combine in many ways to
create the variety and complexity we see around
Examples of Elements
 Hydrogen
 Oxygen
 Silver
 Copper
RELATIONSHIP BETWEEN ELEMENTS,
ATOMS AND MOLECULES
Atoms
 Atom
consists of electrons, protons
and neutrons.
Atomic Mass
 Atomic
mass of an atom is the sum
of the masses of its protons and
neutrons.
 For
example , Mercury has atomic
mass =80+120 = 200 atomic mass
units (a.m.u.)
Atomic Number
 Atomic
number of an atom is only
the number of protons the atom has.
 For
example, the atomic number of
mercury(Hg) is 80.
Arrangement of Electrons around
the Nucleus
 Electrons
move around the nucleus
in shells or orbits.
Number of electrons in each shell
 The
first i.e. the innermost shell can
take on only two electrons
 Maximum eight electrons can move
in the second shell.
Neon
Shells contd..
 The
next shell can take maximum of
8 electrons.
 Beyond
this, the size of shells
increases, thus they have smaller
shells called sub-shells
Order of filling shells
 The
shells are filled from innermost
to the outermost.
Neon
Sodium
Magnesium
Inertness


When a shell gets
filled,
the
atom
becomes
chemically
inert.
Helium, Neon, Argon
have their shells full, so
they are chemically
unreactive.