Introduction

Made By :- Sanyam Ohra Class :- IXth A

Submit To :- Veer Sir Roll No :- 20

Particles

• Atoms• molecules

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

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

ATOMIC STRUCTURE

ATOMIC STRUCTURE

PropertiesParticle 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

Atoms

• Sub-atomic particles• Electrons• Protons• Neutrons

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

ELECTRONS

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

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

NEUTRONS:

• small particles with no charge • reside in the nucleus • along with the proton, make up most of the

mass of the atom

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

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

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

Molecules

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

EXAMPLES OF MOLECULES

Examples of molecules

Representing molecules

• Names: ethanol, ethyl alcohol

•Formulas: C2H8O, C2H5OH, CH3CH2OH

•Structural drawings

•Models