1. Introduction
Made By :- Sanyam Ohra
Class :- IX th A
Submit To :- Veer Sir
Roll No :- 20

2. Particles
• Atoms
• molecules

3. What's an atom?
Definition:
A microscopic small particle that could not
be made any smaller and still behave as a
chemical system. Atoms are the smallest
particles that can exist and represent
elements identity. Atoms cannot be
created or destroyed

4. Atoms
• Atoms consist of protons, neutrons, electrons
• The atomic structure is shown in the diagram
below
• Protons have positive charge
• Electrons have negative charge
• Neutrons have no charge

5. ATOMIC STRUCTURE

6. ATOMIC STRUCTURE

7. Properties
Particle Mass (kg) Mass (amu)# Charge*
Electron 9.10939 x 10 -31 0.00055 = 0 -1
Proton 1.67262 x 10 -27 1.00728 = 1 +1
Neutron 1.67493 x 10 -27 1.00866 = 1 0

8. Atoms
• Sub-atomic particles
• Electrons
• Protons
• Neutrons

9. ATOMIC PARTICLES:
• Atoms consist of three subatomic particles:
• electrons
– electrons are negatively charged particles and their
properties are summarized in the following table
• protons
– protons are positively charged particles and their
properties are summarized in the following table
• neutrons
– neutrons have no charge and their properties are
summarized in the following table

10. ELECTRONS
• Small negatively charged particle
• Orbit, circle, around the nucleus
• Have no mass.
• Atoms are neutral.
• Number of electrons = number of protons

11. PROTONS:
• small, positively charged particles
• reside in the nucleus
• along with the neutron, make up most of the
mass of the atom
• the number of protons is what defines the
type of a particular atom.
• Atoms are neutral
• Number of protons = number of electrons

12. NEUTRONS:
• small particles with no charge
• reside in the nucleus
• along with the proton, make up most of the
mass of the atom

13. ATOMS--Dalton's Atomic Theory
• All matter (including elements) is composed of
atoms; each atom is a very small, chemically
indivisible particle
– the word 'atom' is from the Greek word "atmos"
which means "cannot be cut apart"
• elements are different because they are
composed of different types of atoms
• each type of atom has properties different
from other atoms

14. Atomic theory of matter
• Matter composed of atoms
• Atoms of given element have identical
properties
• Different elements have different properties
• Atoms combine in whole number ratios
• Not created or destroyed in ordinary chemical
reactions

15. What's a molecule?
Definition:
The smallest particles of an element or
compound that can exist and retain the
chemical properties of that element or
compound

16. Molecules
•Molecular formula gives composition:
number of atoms of each element
present
•Molecular mass= sum of masses of
atoms

17. EXAMPLES OF MOLECULES

18. Examples of molecules

19. Representing molecules
• Names: ethanol, ethyl alcohol
•Formulas: C2H8O, C2H5OH, CH3CH2OH
•Structural drawings
•Models