9th Chemistry, Ch 1 - Lecture 11 - Types of Molecules

Molecule:-

Molecule is formed by chemical combination of atoms. These atoms may be same or different. Molecule is the smallest unit of element or compound. There are different types of molecules depending upon the number and types of atoms combining. Some types of molecules are as follows:-

Atoms jb chemically milte hn to molecule bnate hn. Ye atoms ek jese b ho skte hn or different b. Compound ya element k smallest particle ko molecule bolte hn. Number of atoms or kind of atoms ki bases pr molecules ko different types me divide kiya jata ha.

Monoatomic molecule:-
A molecule madeup of only one atom is called monoatomic molecule.
For Example:- Inert gases helium(He), neon(Ne) and argon(Ar).

Aase molecules jin me sirf 1 atom ho unhe hm monoatomic molecules bolte hn.

Diatomic molecule:-
A molecule madeup of two atoms is called diatomic molecule.
For Example:- hydrogen(H2), oxygen(O2), chlorine(Cl2) and hydrogen chloride(HCl).

Aase molecules jo k 2 atoms k milne se bnte hn inhe hm diatomic molecules bolte hn.

Triatomic molecule:-
A molecule madeup of three atoms is called triatomic molecule.
For Example:- H2O, CO2.

Molecules jo k 3 atoms k milne se bnte hn inhe hm triatomic molecules bolte hn.

Polyatomic molecule:-
A molecule madeup of many atoms is called polyatomic molecule.
For Example:- CH4, H2SO4, C6H12O6.

Molecules jin me bht sare atoms majood hon unhe hm polyatomic molecules bolte hn.

Homoatomic molecule:-
A molecule madeup of same type of atoms, is called homoatomic molecule.
For Example:- H2, O2, S8, P4.

Ase molecules jo k 1 hi trha k atoms k milne se bnte hn unhe homoatomic molecules khte hn.

Heteroatomic molecule:-
A molecule madeup of different kinds of atoms, is called heteroatomic molecule.
For Example:- CO2, H2O and NH3.

Molecules jo k different atoms k milne se bnte hn unhe hm heteroatomic molecules bolte hn.

Written By:- M.Ashir Azeem

9th Chemistry, Ch 1 - Lecture 10 - Differences

Difference between Atoms and Ions

1.Atom:-
Atom is the smallest particle of an element.

Element ka sb se chota particle atom hota ha.

1.Ion:-
Ion is the smallest unit of an ionic compound.

Ionic compound ka sb se chota unit ion hota ha.

2.Atom:-
Atom can or cannot exist independently and can take part in a chemical reaction.

Atom akela b rh skta ha or group ki shakl me b or atom chemical reactions me b hissa leta ha.

2.Ion:-
Ion cannot exist independently and is surrounded by oppositely charges ions.

Ion akela ni rh skta ye hmesha group ki form me majood hota ha. or hr ion k apne opposite charge wale ions se ghira rhta ha.

3.Atom:-
Atom is electrically neutral.

Atom electrically neutral ha mtlb k atom me se electricity pass ni kr skti.

3.Ion:-
Ion has a net charge on it.

Ion k uper net charge hota ha, jo k positive b ho skta ha or negative b.

Difference between Molecule and Molecular Ion

1.Molecule:-
It is the smallest particle of an element or compound which can exist independently and shows all the properties of that compound.

Element ya compound k sb se chote particle ko hm molecule bolte hn jo k independently b mil skta ha oe compound ki sari properties show krta ha.

1.Molecular Ion:-
It is formed by gain or loss of electrons by a molecule.

Jb koi molecule electrons lose krta ha ya phir electrons add krta ha to wo molecular ion bnata ha.

2.Molecule:-
Molecule is always neutral.

Molecule hmesha neutral hota ha.

2.Molecular Ion:-
It can have negative or positive charge.

Molecular ion pr positive charge b ho skta ha or negative b.

3.Molecule:-
It is formed by the combination of atoms.

Molecule atoms k milne se bnta ha.

3.Molecular Ion:-
It is formed by the ionization of molecule.

Molecule ki ionization krna se molecular ion bnte hn.

4.Molecule:-
Molecule is a stable unit.

Molecule stable rhta ha.

4.Molecular Ion:-
It is a reactive species.

Molecular ions reactive hote hn.

Difference between Ions and Free Radicals

1.Ions:-
Ions are the atoms which have some charge.

Ions aase atoms ko bolte hn jin pr koi charge majood ho.

1.Free Radicals:-
Free Radicals are the atoms that have odd number of electrons.

Aase atoms jin me odd number of electrons majood hon unhe hm free radical bolte hn.

2.Ions:-
Ions exist in solution or in crystal lattice.

Ions solution ki form me b milte hn or crystal lattice ki form me b.

2.Free Radicals:-
They can exist in solution as well in air.

Free radicals solution me or hawa me b majood hote hn.

3.Ions:-
Their formation is not affected by the presence of light.

Ions k bnne me light k hone ya na hone se kuch fark nhi prta.

3.Free Radicals:-
They may form in the presence of light.

Free radicals light ki majoodgi me bnte hn.

Written By:- M.Ashir Azeem

9th Chemistry, Ch 1 - Lecture 9 - Chemical Species

Ions:-
Atoms or group of atoms having some charge on it, is callen an ion.

Atoms ya group of atoms k uper agr kuch charge ho to ise hm atom ni bl-k ion bolen ge. Ye charge positive b ho skta ha or negative b.

Cation:-
An Atom or group of atoms having positive charge on it, is called cation.
For Example:- Na+, K+

Atom ya group of atoms pr agr positive charge ho to ise hm cation bolte hn jesa k uper example me dekhaya gya ha. Atom k uper positive charge tb ata ha jb atom k outermost shell me se electrons bahir nekl jyn.

Anion:-
An atom or group of atoms having negative charge on it, is called anion.
For Example:- Cl-, O-2

Atom ya group of atoms pr agr positive charge ki jga negative charge aa jy to isy hm anion bolte hn jis ki examples uper di gien hn. Atom k uper negative charge tb ata ha jb bahir se koi electron us atom me add ho jy.

Molecular Ion:-
When a molecule gains or loses an electron, it forms a molecular ion.
For Example:- He+, N+

Jesa k hmne uper prha k agr kisi atom me koi electron add kiya jy ya phir us atom me se koi electron nikala jy to use hm ion bolte hn. Isi trha agr kisi molecule me se hm koi electron bahir nekalen ya us molecule me electron ko add kren to phir ise hm molecular ion bolen ge.

Free Radicals:-
Atoms or group of atoms having odd number of (unpaired) electrons, are called free radicals.
For Example:- H•, Cl•, H3C•

Agr kisi b atom ya group of atoms me odd number of unpaired electrons majood hon to unhe hm free radicals bolte hn. Free radicals ko atom ya group of atoms k symbol k uper right side pr dot se zahir kiya jata ha. Free Radicals tb bnte hn jb koi bond equally divide krta ha. Free Radicals bht hi reactive hote hn or ye bht hi jldi apna octet pura kr lete hn

Written By:- M.Ashir Azeem

9th Chemistry, Ch 1 - Lecture 8 - Empirical and Molecular Formula

Empirical Formula:-
The simplest whole number ratio of atoms present in a compound is called empirical formula.

Kisi b compound k formula ko me majood components ko simple ratio k sath likha jy to usy hm empirical formula bolte hn.
For Example:- Glucose me carbon, hydrogen or oxygen majood hote hn or in ki simple ratio 1:2:1 ki hoti ha to is liay glucose ka empirical formula CH2O ha.

Formula Unit:-
The simplest whole number ratio of ions, as present in the ionic compound, is called formula unit.

Empirical formula me majood ions ki simple ratio ko hm formula unit bolte hn.
For Example:- Common Salt ka empirical formula NaCl ha or is k formula unit me 1 Na+ ion or 1 Cl- ion majood hota ha.

Molecular Formula:-
The formula that show actual number of atoms of each element present in a molecule of that compound, is called molecular formula.

Aasa formula jo kisi b compound k molecule me majood tmam elements k actual numbers ko show kre use hm molecular formula bolte hn.
For Example:- Benzene ka molecular formula C6H6 ha. Jo k hme btata ha k benzene k molecule me 6 carbon k atoma or 6 hi hydrogen k atoms majood hn. Benzene ka ye molecular formula is k empirical formula se nekala gya ha jo k CH ha. Molecular formula ko empirical formula se derive krne k liay hm is formula ko use krte hn.
Molecular formula = (Empirical formula) n
Where n is 1,2,3 and so on.

Molecular Mass:-
The sum of atomic masses of all the atoms present in one molecule of a substance, is called its molecular mass.
For Example:- Molecular mass of water (H2O) is 18 amu, of carbon dioxide (CO2) is 44 amu and that of chlorine (Cl2) is 71 amu.

Molecule me majood tmam atoms k atomic masses ko sum kren to is total mass ko hm molecule ka mass ya phir molecular mass bolte hn.
For Example:- Water (H2O) k molecule me 2 hydrogen or 1 oxygen ka atom majood ha or agr hn in sb atoms k atomic masses ko jma kren to hme water k 1 molecule ka mass mil jy ga jo k 18 amu hota ha. Isi trha carbon dioxide (CO2) me 1 carbon or 2 oxygen k atoms majood hn or is ka molecular mass 44 amu ha. Or isi trha chlorine (Cl2) me 2no hi atoms chlorine k hn or in k atomic masses ko sum krne se hmare pass chlorine molecule ka mass aa jata ha jo k 71 amu ha.

Formula Mass:-
The sum of masses of all the atoms present in one formula unit of a substance is called its formula mass.
For Example:- Formula mass of CaCO3 is 100 amu and that of sodium chloride (NaCl) is 58.5 amu.

Substance k formula unit me majood tmam ions k masses ko sum kren to hm is total mass of us substance ka formula mass bolen ge.
For Example:- CaCO3 k formula unit me 1 calcium, 1 carbon, or 3 oxygen majood hn is formula unit k sb masses ko jma krne se hme formula mass mil jata ha jo k 58.5 ha. Isi trha sodium chloride (NaCl) k formula unit me 1 Na+ ion or 1 Cl- ion ha in k masses ko jma kren to use hm formula mass bolte hn jo k 100 amu ha.

Written By:- M.Ashir Azeem

9th Chemistry, Ch 1 - How to write a chemical formula? - Lecture 7

How to write a chemical formula?

As you know that k elements are represented by symbols like that compounds are represented by chemical formulae.

Jis trha se hm elements ko symbols k zreay show krte hn isi trha compounds ko likhne k liay hm chemical formula likhte hn.

To write chemical formula following steps would be kept in mind.

1. In chemical formula of compound symbols of elements are written side-by-side, in the order of positive ion first and then negative ion.

Chemical formula me majood elements ko un k symbols se zahir kiya jata ha, jis me positive charge wale ion phle or negative charge wale ion ko bad me likha jata ha.

2. The valencies of each ion is written on the top right corner of its symbol, e.g, Ca+, Na+, Cl- and O-2.

Har ion ki valency us k symbol k upper right corner pr likhi jati ha. jesa k calcium ki valency +1 ha jo k is k symbol (Ca) k uper right corner pr likhi jy gi Ca+. or isi trha age negative ion ko dekhen to oxygen ki valency -2 ha to isy b O k uper right corner pr likhen ge O-2.

3. The valencies of each ion is brought to lower right corner by 'cross-exchange' method. e.g,

Chemical formula likhte huay ions ki valency ko un k symbol k niche right corner pr cross-exchange method k zreay shift kiya jata ha. jesa k uper example me btaya gya ha k NaCl me sodium ka positive ion chlorine k neche right corner pr or chlorine ka negative ion sodium k neche right corner pr cross-exchange method k zreay shift kiay gy hn. isi trha CaCl2 or CaO k ions ki valency ko b isi method k zreay shift kiya gya ha.

4. If the valency of both the ions are same then it is not written in the formula but if they are different then they will written at the positions which are described above.

Agr compound me majood dono ions ki valency same ho to un ki valency chemical formula likhte huay ni likhi jati. Jin ions ki valency different ho unhi ko cross-exchange method k zreay likha jata ha. jesa k uper example me b btaya gya ha k NaCl k dono ions ki valency 1 ha to is k chemical formula me 1 ko ni likha gya lakin CaCl2 me calcium ion pr +2 or chlorine k ion pr -1 charge ha, is liay cross-exchange method k zreay ions k valency in k nechy ki trf shift kr di gi ha.

5. If there is a radical in the compound instead of ion, which carry a net charge on it, it will also written as explained in the above points. For Example:- in Al2(SO4)3 , SO4 is a radical which has a net charge of -2 and the aluminum ion carry +3 charge, so both the valencies are shifted by cross-exchange method.

Agr compound k chemical formula me ion ki jga radical majood ho, jis pr net charge likha jata ha to use b same isy process k zreay likha jata ha jo k uper k points me smjaya gya ha. For Example:- Al2(SO4)3 , me SO4 ek radical ha jis ks net charge -2 ha or is k sath wale aluminium k ion pr +3 ka charge ha, jinhe cross-exchange method k zreay shift kr diya gya ha. jesa k uper wale points me smjaya ja chuka ha.

Written By:- M.Ashir Azeem

9th Chemistry, Ch 1 - Atomic and Mass Number - Lecture 6

Atomic Number:-
Atomic number of an element is equal to the number of electrons, or protons present in the nucleus of the atom of that element. It is represented by 'Z'.

Element k atom k nucleus me majood protons ki tadad ko hm atomic number bolte hn or atomic number ko 'Z' se represent kiya jata ha.

All the atoms of an element have same number of protons in their nucleus. It means that every element have its specific atomic number and it is also termed as the identification of the element.
For Example:- All atoms of hydrogen have 1 proton in their nucleus so the atomic number of Hydrogen is 1. Same like that, Carbon atoms have 6 protons in their nucleus and oxygen have 8 protons, So the atomic number of carbon and oxygen is 6 and 8 respectively.

Kisi b element me majood tmam atoms k nucleus me majood protons ki tadad ek jesi hoti ha. Iska mtlb ha k har element ka ek fixed atomic number hota ha. Jis number se hm us element ko asani se phchan sekte hn. Isi number ko hm atomic number bolte hn.
For Example:- Hydrogen k nucleus me 1 proton majood hota ha is liay hydrogen ka atomic number 1 ha. Isi trha carbon k nucleus me 6 protons or oxygen k nucleus me 8 protons hote hn is liay carbon ka atomic number 6 or oxygen ka atomic number 8 hota ha.

Mass Number:-
Mass number of an element is equal to the sum of the number of protons and neutrons present in the nucleus of the atoms of that element.It is represented by 'A'.

Element k atom k nucleus me majood protons or neutrons dono ki tadad ko hm mass number bolte hn or mass number ko 'A' se represent kiya jata ha.

Most of elements have same number of protons and neutrons in their atom but not all the atoms.
For Example:- Hydrogen atoms have 1 proton and no neutron, So its mass number will be 1. Carbon atom has 6 protons and 6 neutrons, So its mass number will be 12. Sodium atom has 11 protons and 12 neutrons, So its mass number will be 23.

Elements k atoms k nucleus me protons or neutrons dono ki tadad ko hm mass number bolte hn. Protons or neutrons ki ye tadad kuch elements me same b hoti ha or kuch elements me in dono ki tadad mukhtlif b hoti ha.
For Example:- Hydrogen k atom k nucleus me 1 proton hota ha jb k koi b neutron nhi hota, is liay hydrogen ka mass number b is k atomic number ki trha 1 ha. Is k ilawa carbon k atom me 6 protons or 6 hi neutrons majood hote hn is liay carbon ka mass number 12 ha.

Relative Atomic Mass:g

The relative atomic mass of an element is the average mass of the atoms of that element as compare to the 1/12th the mass of an atom of carbon-12 isotope.

Atomic Mass Unit:-
The unit of relative atomic mass is 'atomic mass unit'. It is represented as 'amu'.

1 amu = 1.66 × 10(-24)g

As you know that the side of an atom is very small. So, it can not be determined practically. That's why scientists gives a way to determine the size of an atom by comparing the size with the atom of carbon-12 isotope. So, by comparing the sizes with C-12 we can easily determine the size of any atom.

Jesa k apko pta ha k atom ek bht hi chota particle ha jise hm aam ankh se dekh b nhi skta, to itne chote particle ka structure maloom krna yakeenan bht mushkil kam ha, is liay scientists ne atom k structure ka pta krne k liay ek method nekala ha jise hm Relative atomic mass bolte hn. Is process k zreay hm kisi b atom k mass ko carbon-12 isotope k mass k sath compare kr k maloom kr skte hn. Relative atomic mass k unit ko atomic mass unit bolte hn jise 'amu' likha jata ha. 1 amu = 1.66 × 10(-24)g

Written By:- M.Ashir Azeem