nature of matter science, ix. module objectives introduction structure of matter historical...

Nature of MatterScience, IX

Module Objectives

• Introduction• Structure of Matter• Historical background and different law’s.• Modern Periodic Table• Chemical Equation• Balancing Chemical Equation• Types of Chemical Equation• Chemical Reactions and Types• Chemical Bond and Types

Introduction

• The entire universe is made of two things: matter and energy. For the time being we will concern ourselves with matter only.

• Objects that take up space and have mass are called matter.• mass characterizes an object's resistance to a change in its

motion.• Everything around you is made up of matter. Chocolate cake is

made up of matter. You are made of matter.• Remember all objects that take up space and have mass are

called Matter.• What isn’t Matter? : Light , Carrot , Water

Structure of Matter

• ATOMS: The basic building blocks of everything you can see . ATOMS are indivisible part of anything you see around.

• Atom contains proton , neutron and electron.

• ELEMENT: Any material that is composed of only one type of atom is called element

• The atoms in oxygen are identical to each other. The atoms in hydrogen are identical to each other. However, the atoms of oxygen are different from the atoms of hydrogen.

Structure of Matter

• Molecule: A molecule is formed when two or more atoms join together.

• A compound is a molecule that contains at least two different elements.

• Molecular hydrogen (H2), oxygen (O2) and nitrogen (N2) are not compounds because each is composed of a single element.

• Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element.

• Isotope: Element with same number of protons but differs in neutrons , Ex. Carbon -12 , Carbon -13

Structure of Matter

• Classification of elements are done based on the properties it possessed..

• Atomic number : Number of protons in an atom , Represented as A

• Atomic Mass : Protons + Neutrons , Represented as Z

• Valence electrons : electrons in the outermost level and they are highly reactive

• Monovalent : Atom which contains single valence electron

Dobereiner's Law of triads

• Classified elements into group of three and called them as triads.

• Placed elements in ascending order of atomic mass and observed similarity in properties

• Atomic mass of the middle element of the triad is equal to the mean of the atomic masses of the other two elements of the triad

Drawbacks of Dobereiner's Law

• All the then known elements could not be arranged in the form of triads.

• Law was not holding good for very low mass or for very high mass elements, the

• Take the example of F, Cl, Br2

Element A Z

F 9 18.99

Cl 17 35.5

Br 35 80

Newlands law of octaves

• Ocata means Eight

• Elements were arranged in the ascending order of the their atomic mass , the eighth element resembled the first element in its properties

• properties of lithium and sodium are similar

• Drawbacks • It was not valid for elements that had atomic

masses higher than Ca.• When more elements were discovered, such

as elements from the noble gases such as He, Ne, Ar, they could not be accommodated in his table.

Mendleev’s Periodic Table

• Mendleev considered both atomic mass and similarity of properties

• Arranged elements in ascending order of atomic mass in horizontal rows

• He starts with the new horizontal row once he finds the element with the similar properties.

• Sometimes this method of arranging elements meant there were gaps in his horizontal rows or 'periods'. But he considered them as uncovered elements

Modern Periodic Table

• Based on Atomic Number

• Properties of the elements are the periodic functions of their atomic number

• A periodic table is a tabular display of the chemical elements, organized on the basis of their atomic numbers, electron configurations, and recurring chemical properties.

• Horizontal 7 rows are called periods

• Vertical 18 columns are called Groups

Chemical Equation

Symbol Meaning

Left Hand Side Molecular Formula of reactants

Right Hand Side Molecular Formula of Products

Reactants are joined by Plus ( +) Sign

Reversible Chemical Reaction

Above the arrow Reaction Conditions

Gases

Precipitates

Example

Balancing Chemical Equation

• During Chemical Reaction position of atom changes

• Law of Conservation of matter : Matter can neither be created nor destroyed

• Hence Number of atoms present in reactants should be equal to products

Balancing Chemical Equation

Types of Chemical reaction

• Chemical combination

• Chemical decomposition

• Chemical displacement

• Chemical double decomposition or double Displacement

Decomposition

Double Displacement

Chemical Combination

• Two or more reactants combine chemically to form a single product

Chemical Decomposition

• Single reactants decomposes to form two or more product

Chemical Displacement

• Element present in compound is displaced by another element

Example

Chemical Double Decomposistion

• Reactants will exchange mutually their radicals to form two new compoundsExample

Chemical Bond

• Factor which determines the properties of Compound

• Strong linkage which binds atoms to form its molecules

• Its not a attraction or repulsion

• Equilibrium between attraction and repulsion , so that the atoms are held at particular distance

Ionic or Electrovalent Bond

• Examples : Salt (NaCl) , Washing Soda (Na2 Co3), blue vitriol (CuSo4 , 5H2O),Ammonium Chloride (NH4Cl) , Baking Soda(NaHCO3)

• Melting and Boiling points are very high

• Soluable in water but not in organic solvents.

• Good Conductors of electircity in molten state also

Ionisation

• Its Process , in Which Ionic compounds dissolve in water and disassociate into their ions.

• Its reversible process

Types of Ions

• Positively Charged Ions or Cations

• Negatively Charged Ions or Anions

Covalent Bond

• A covalent bond is the chemical bond that involves the sharing of pairs of electrons between atom

• Covalent bond between atoms of same element forms molecule of that element

• Ex. H2 , Cl2

• Covalent bond between atoms of different elements forms molecule of covalent compound

• Ex. Methane , Wax,Hydrageon Chloride (HCl2 )• If electron distributions are equal then its

called as equal nuceli covalent bond or non polar covalent compound

Ionic Vs Covalent

Polar / Dipole Bond

• Polar Bond : A type of covalent bond between two atoms in which electrons are shared unequally

• Polar Molecule : Molecule in which one end has a positive electrical charge and the other side has a negative charge

• H2O is called polar molecule .

Behavior of Metals

• Posses smooth and lustrous surface

• Light cannot pass through thin metal foils

• Good conductors of head and electricity

• Malleable and Ductile

• Thermo ionic in nature meaning they emit electrons on heating

• Cooking Vessels are made using metals

Metallic Bond

• Reaction between molecules within metals called alkali reactive force

• It is the sharing of a sea of delocalized electrons amongst a lattice of positive ions

Hydrogen Bond

• attractive (dipole-dipole) interaction between an electronegative atom and hydrogen atom bonded to another electronegative atom.

• This bond always involves a hydrogen atom• Hydrogen bonds can occur between molecule or within parts of a single

molecule.• weaker than covalent or ionic bonds