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answers were of gr88 help

Q...if [x-2]⁶ +[x-4]⁶ =64 then the equation has

a ] real and irrational roots

b] real and rational roots

c] two real and two irrational

d] none

Q..if p>2 and then the equation x³ -px+1=0 cannot have

a]rational roots b] integral roots

c]irrational roots d] none

Q..if a, b are the roots of x² +px+q=0 and x²ⁿ +pⁿxⁿ+qⁿ=0 and a/b,b/a are the roots of xⁿ +1+{x+1^}n=0 then n must be

a]even integer b]rational but not integer

c]odd integer d] none

where a and b are alpha and beta

movement of lone pairs away from -OH group is +r effect.

Q..let A{1,2},B{3,4},C{x,y}be a pt such that {x-1}{x-3} +{y-2}{y-4}=0 if

ar{triangleABC}=1 then max no of positions of positions of C in the xy

plane???

Q.. IF THE LINE ax+y+1=0, x+by+1=0 nd x+y+c =0{a ,b nd c being distinct nd different from 1 }are concurretnt then 1/1-a + 1/1-b + 1/1-c is equal to...

Q..A train A runs from east to west nd another train B of the same mass runs from

west to east at the same speed along the equator A presses with the force F₁

nd B presses the track with force F_2 ..

a} F₁ > F₂ b} F₁< F₂

c} F₁ = F₂ d} information is insufficient

Q..A rod of length 20cm pivoted near an end nd which is made to rotate in a horizontal
plane with a constant angular speed .A ball of mass m is suspended by a string also of
length 20cm from the other end of the rod if the angle made by the string with the vertical is 30⁰. find the angular speed of the rotation?

Q..A block of mass m is pushed against a spring of spring constant k fixed at one end to a wall the block can slide on a frictionless table. the natural length of the spring is L₀ it is compressed to half its natural length when the block is released.

Find the velocity of the block as a function of its distance x from the wall ??

very precise nd superbbbbbbbb

Q,.a >0 b>0 nd a+b =1 show that {a +1/a}²+{b + 1/b}²

25/2??

Q.find a three digit number such that its digits are in GP nd the digits of

the number obtained from it by subtrating 400 form an AP??

Q.. let a₁ a₂ ......a_n a_n+1 ......be an AP

S₁ =a₁ +a₂+ a₃+.....+a_n

S₂ =a_n+1 + a_n+2+......+a_2n

S₃= a_2n+1+a_2n+2+ ....a_3n

..............

prove that the sequences S₁ ,S₂ ,S₃ ...... is an arithmetic progression whose

common difference is n² times the common difference of the given progression.

Q.how much energy would be evolved when a helium nucleus combines with two

electrons to form the ground state helium atom ??

the first ionisation energy of He is 24.6 eV.

Q. For an e in a hydrogen atom the wave function y is proportional to e^-r/a0,where

a₀is the bohr's radius .what is the ratio of finding the e at the nucleus to the probability of finding it a_0.

but i can see them on my comp.

As we increase the number of protons, the number of electrons also increases.

As we start to get more and more negative electrons around the nucleus, they will start to repel each other (Electrons have the same charge, and remember that same charges repel). For this reason, the electrons that orbit the nucleus cannot be all bunched together. Like the protons in the nucleus they need to be kept apart. So electrons orbit the nucleus at different distances, forming layers or 'shells' of electrons. This is a little bit like the planets orbiting the sun.

In lithium, the 3 electrons are in shells: two in the first, and one in the second shell.

The first shell can hold 2 electrons before it is full, the bigger second shell can hold up to 8, the third shell up to 18. Because we know the maximum number of electrons in each shell, we can accurately draw the atomic structure of Oxygen (lets think of the nucleus as one blob in this diagram rather than drawing all the protons and neutrons).

Protons	Neutrons	Electrons	Element Name
8	8	8	Oxygen

Oxygen has 8 protons, therefore it must have 8 electrons. We know that 2 of these electrons can fit into the first shell, and the remaining 6 go into the second shell (which can hold 8).

When scientists write down a description of an element, they try to show all the information needed to draw the diagrams, and there is a method for doing this. Let's look at the standard way of writing Hydrogen, Oxygen, and Fluorine :

The letter is the CHEMICAL SYMBOL for the element.
The top number is the MASS NUMBER: the sum of the protons and neutrons.
The bottom number is the ATOMIC NUMBER: the number of protons or the number of electrons (as there are the same number of protons and electrons in an atom).

Using these descriptions we can work everything out for the third example, fluorine, even though we have not talked about flourine yet.

Flourine has the chemical symbol F. The ATOMIC number tells us that It has 9 protons and 9 electrons. The MASS number, representing protons and neutrons, is 19. We already know that there are 9 protons, so the other 10 are neutrons. Try to work out the same answers for Hydrogen (H) and Oxygen (O).

Stability.
Every atom wants to be stable, and stability for an atom is achieved by having the right number of electrons in its outermost shell. As we have seen, each shell has a maximum number of electrons that it can hold, but shells also have an ideal number of electrons. If the outermost shell of an atom contains this ideal number, it will be a stable atom.

If the outermost shell does not contain this ideal number, the atom will strive to achieve stability by gaining or losing electrons in their outer shell. If this cannot be achieved by shuffling their own electrons around, atoms interact or react with other atoms to take or share electrons to achieve their goal.

Atoms that already have the ideal number of electrons in their outer shell have no desire for more electrons, and don't want to lose any either. These atoms tend to be unreactive or inert. Atoms that that do not have the ideal number tend to be reactive, striving to get their hands on more, or get rid of some electrons.

The table below lists shells one to five, and shows the maximum number of electrons each shell can hold, but also the ideal number fot the atom to be stable if that shell is the outermost shell..

Shell	Can hold	is stable with an outer shell holding
1	2	2
2	8	8
3	18	8
4	32	8
5	50	8

Lets think about two atoms that we are familiar with: Helium and Oxygen.

Helium has 2 electrons in its outer shell.
This is the ideal number for the first shell, so as we would expect, Helium is unreactive and inert.

Oxygen has 2 electrons in the first shell, but only 6 in its second outer shell.
This is not the ideal of 8 electrons in the second shell. We would expect oxygen to do something about this, and try to get 2 more electrons from somewhere by reacting with another atom. This is indeed the case, and oxygen gets involved in many reactions with other atoms.

Wait a minute - where are the neutrons ?
We know that opposite charges attract each other, but the converse is also true - the same charges repel each other. When there is just one proton in the nucleus (like the Hydrogen we just looked at), there isn't a problem, but if we had two protons in the nucleus, lying side by side, they would repel each other. They need something to keep them apart. Enter the neutron. If we draw another element, with two protons in the nucleus, we have a different element - Helium.

It is the number of protons in an atom that determines which element it is.

Because Helium has 2 protons, it needs 2 electrons to be charge neutral (2 positives need 2 negatives). Also notice that Helium has 2 neutrons in the nucleus to keep the positive protons from repelling each other and breaking the atom apart. Because neutrons do not have a charge, they do not affect the overall charge of the atom.

We could carry on drawing bigger atoms with increasing numbers of protons, neutrons, and electrons. If we did this, we would draw the elements described in the table below :

Protons	Neutrons	Electrons	Element Name
1	0	1	Hydrogen
2	2	2	Helium
3	4	3	Lithium
4	5	4	Beryllium
5	6	5	Boron
6	6	6	Carbon
7	7	7	Nitrogen
8	8	8	Oxygen
9	10	9	Flourine

ATOMIC STRUCTURE

All things around us are made of atoms. The clothes we wear, the buildings we live in, the air around us, even our own bodies. Atoms are the microscopic building blocks of every solid, liquid or gas. If all the atoms in a substance are the same type - it is called an element. This means it cannot be broken down into any "ingredients". Oxygen (chemical symbol O) is a pure element. Oxygen is oxygen - it is not made up of anything else. If a substance contains more than one element, it is either a compound or a mixture. We will discuss these later, for now let's stick to elements.

We said before that elements have no "ingredients" - but actually they do. Even a tiny atom is built of smaller building blocks. All atoms are built of 3 basic things : Protons, Neutrons, and Electrons.

The simplest atom is Hydrogen. A hydrogen atom is built of one proton and one electron. The proton sits in the centre of the atom and forms the nucleus of hydrogen. The electron spins around the nucleus - a bit like a moon orbiting a planet. Hydrogen, as you can see in the diagram below, does not have any neutrons. Larger atoms have many protons and neutrons in their nucleus, and have many orbiting electrons.

So why doesn't the electron just spin off ? Why does it stay orbiting the nucleus?

The answer is that the electron is attracted to the nucleus because of its 'charge'. Electrons have a negative charge and protons have a positive charge (neutrons do not have a charge). Opposite charges attract each other.

Need help to understand charge attraction? This is why clothing taken from the drying machine 'clings'. A static charge is formed when the clothing rubs together in the machine, and this builds up a negative charge. The negative clothing is then attracted to more positively charged things around it.

The force caused by the spinning, which should cause the electron to spin off away from the nucleus, is balanced by the charge force attracting the electron towards the nucleus. So it doesn't fly off OR cling to the nucleus, it spins around being pulled equally in both directions.

Although the proton has a positive charge, and the electron has a negative charge, the atom itself has no charge - it is neutral. All atoms have the same number of negative orbiting electrons as they have positive protons in their nucleus (each '+' is cancelled out by a '-'). If you have trouble grasping this - just do the maths. Every proton is +1, every electron is -1, and the total of all protons and electrons has to be zero.

awesome gr888 work.......////

really wonderfull presentation