Particulate Nature of MatterMatter- anything that has mass and occupies

spaceParticle + particle = matter

Iron (Fe) from iron atom

NaCl from sodium ions and chloride ion

H2O from water molecules

Atomsan atom is the smallest particle of an element example : “O” for oxygen atom

Moleculescontains two or more atoms which are bonded together ( maybe same element or not )example : H2 and CCl4

Ions-ions are charged either positive or negative-are form in liquid or molten state-lose electron (+ ion),gain electron (- ion)example : Na+ , Mg2+ , Br-

Kinetic Theory of MatterSolids

- strong forces of attraction - particle only vibrate (fixed shape and volume)

Liquids- force of attraction weak than solid- particle can move around (follow container shape)

Gases- no attraction between particles- particle move faster and freely (zigzag)

Diffusion- example : perfume- light and small particle diffuse faster- heavy and large particle diffuse slow

The Atomic StructureDemocritus

Democritus proposed that if a piece of gold cut into smaller until cannot cut anymore, called atom.

John Dalton (1766-1844)

J.J.Thomson (1856-1940)

Ernest Rutherford (1871-1937)

Neils Bohr (1885-1962)

James Chadwick (1891-1974)

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John Dalton(1766-1844)In 1808, he proposed :1.All matter is composed of atoms.2.Atoms cannot be created or destroyed.3.All the atoms of an element are identical.4.The atoms of different elements are different.5.When chemical reactions take place, atoms of

different elements join together to form compounds.

J.J.Thomson (1856-1940)1. It was the first model of the atom.2. 1897- Thomson discovered the electron

(negatively- charged).3. Thomson suggested that an atom is a

positively- charged sphere with electrons embedded in it like a raisin pudding.

Ernest Rutherford (1871-1937)1. 1914- Rutherford discovered the proton2. Rutherford model was based on the alpha

particle scattering experiment3. He proposed

1) all the positive charge of an atom is concentrated in the nucleus2) an atom consists of a positively-charged nucleus with a cloud of electrons surrounding the nucleus

Neils Bohr (1885-1962)He was a student of RutherfordHe proposed

1) electrons are arranged in orbits (electron shells) around the nucleus of the atom2) electrons in a particular path have a fixed energy.

To move from one orbit to another, an electronmust gain or lose the right amountof energy

James Chadwick (1891-1974)He proposed that the nucleus of the atom

contains proton and neutron and the nucleus is surrounded by a cloud of electrons

Atomic structure of an atomAtoms are made of three different types of subatomic

particles called protons, neutrons and electronsProtons and neutrons are found in the nucleus and

they are known as nucleonsNucleus is positively charged because the protons

are positively charged and the neutrons are electrically neutral

Electrons rotate around the nucleus in a certain orbit called shells, just like planets rotate around the sun

SUBATOMIC PARTICLES

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proton

neutronshell

electron

{nucleon

THE PROPERTIES OF SUBATOMIC PARTICLESSubatomic particles

Proton Neutron Electron

Symbol p n e¯

Relative electric charge

+1 0 -1

Relative mass

1 1 _1__

1840

An atom is neutral when it has the same number of protons and electrons

PROTON NUMBERThe number of protons in an atom of an

element

Proton number = number of protons

NUCLEON NUMBERThe sum of protons and neutrons in an

atom element

Nucleon number = number of protons + number of neutrons

The number of protons, electrons and neutrons in a particular atom are given in the Periodic Table by the nucleon number and proton number

A : proton numberZ :nucleon number

X: symbol of an element

The number of protons, electrons and neutrons can be determined from the nucleon number and proton number

A

X Z

Example: (a) Aluminium

The symbol of the element above shows that it is aluminium

Nucleon number = 27Proton number = 13Number of neutron = Aluminium atom has 13 protons, 13 electrons and

14 neutrons

27

Al13

27 – 13= 14

Symbol of elementsMost symbols are taken from the English

name

Element Symbol

Hydrogen

Carbon

Nitrogen

Boron

H

C

N

B

Some symbol are made up of two letters

Some symbols are based on the Latin or Greek name

Zinc Zn

Aluminium Al

Calcium Ca

silicon Si

Silver Ag

Copper Cu

Iron Fe

Gold Au

Isotopes and their importanceAre atoms of the same element with the same

proton no. but different nucleon no. or neutron no.

Isotopes of an element have same chemical properties but different physical properties

Example: H1 H2 H3 , P31 P32

Uses of isotopesMedicine

-Cobalt-60 is a radioactive isotope of cobalt. It decays by giving out gamma radiation. In radiotherapy, maglinant cancer cells are killed by directing a beam of gamma rays towards cancer cells

Agriculture

-radiation from radioisotopes is used to sterilise pests such as insects that destroy crops.

-Fosforus 32 use as fertiliser.Industry

-Gamma radiation is used to detect whether canned food or bottled drink is completely or partially filled