Have you ever thought about orbitals? Why orbitals have definite shape? How many types of orbitals are present? Which orbital have the highest energy? To answer the above question First of all we need to know about What is an orbitals in chemistry?
In atomic theory and quantum mechanics, an atomic orbital is a mathematical function describing the location and wave like behaviour of an electron in an atom.
Mathematical function - mathematical function is a binary relation between two sets that associates that every element of the first set to exactly one element of the second.
Typical example are function from integer to integer or from the real number to real number.
Functions were originally the idealization of how varying quantity depends on another quantity.
For example the position of a planet is a function of time.
This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus.
The term atomic orbital may also refer to the physical region or space where electron, can be calculated or predict by the particular mathematical form of the orbital.
Each orbital in an atom is characterized by a unique set of values of the three quantum number n, l and m which respectively correspond to the principle quantum numbers ( Which shows electrons energy), angular momentum and magnetic quantum number(Vector component).
Each orbitals can be occupied by a maximum of two electrons, each with its own value of spin ms
Atomic orbitals are the basic buildings blocks of the atomic orbital model.
The probability at any point around the nucleus is calculated using Schrodinger wave equation and is represented by the density of the points.
Note:-A mathematically described region around a nucleus in an atom or molecule that may contain zero, one or two electron. Electrons arrange themselves in cloud like region around the nucleus called orbitals.
When a planet moves around the sun, you can plot a definite path for it which is called an orbit. A simple view of the atom looks similar and you may have pictured the electrons as orbiting around the nucleus.
The truth is different, and electrons in fact inhabit regions of space known as orbitals.
Orbits and orbitals sound similar, but they have quite different meanings. It is essential that you understand the difference between them.
Difference between orbits and orbitals:
To plot a path for something you need to know exactly where the object is and be able to work out exactly where it's going to be an instant later. You can't do this for electrons
To understand above paragraph Heisenberg gives Heisenberg Uncertainty Principle says -loosely-that you can't know with certainity both where an electron is and where it's going next.
(What is actually says is that it is impossible to define with absolute precision, at the same time, both the position and the momentum of an electron) That makes it impossible to plot an orbit for an electron around a nucleus.
Is this a big problem? No, if something is imlos7, you have to accept it and find a way around it.
The impossibility of drawing orbits for electrons because orbit is a path of moving electron.
Orbitals Notation
Orbitals have been given names, which are usually given in the form
X type^y
where X is the energy level corresponding to the principle quantum number n : type is a lower case letter denoting the shape or subs hell of the orbital, corresponding to the angular quantum number l : and y is the number of electron in that orbital.
For example, the orbital 1s² ( pronounced as the individual numbers and letters "one's 'was''two"') has two electrons and is the lowest anergy levels (n=1) and has an angular quantum number of l=0, denoted as s.
Why orbitals called SPDF?
What does SPDF stands for - the orbitals names given to groups of line originally noted in the spectra of the alkali metals. These lines groups are called sharp, principal, diffuse and fundamental.
What the orbitals shape means?
The electronic configuration of an atom denoted the distribution of electrons among available shells. At any point in time, an electron can be anywhere, but it's probably contained somewhere in the volume described by the orbital shape.
Electrons can only move between orbitals by absorbing or emmiting a packet or quantum of energy.
The standard notation lists the subs hell symbols, one after another. The number of electrons contained in each subs hell is stated explicitly.
For example the electronic configuration of Boron, with an atomic number of 5, is 1s² 2s² 2p1 or [He]2s² 2p1. The superscript is the number of electrons in the level. For boron, there are two electrons in the 1s orbital and 2 electron in 2s orbital and one orbital in 2p.
The number in front of the energy level indicated relative energy.
For example, 1s is lower energy than 2s, which in turn is lower energy than 2p. The number in front of the energy level also indicates it's distance from the nucleus. The 1s is closer to the atomic nucleus than 2s.
Why s - orbital is spherical?
Orbitals with subs hell quantum number l=0 are called s - orbitals. All s-orbitals are spherical in shape and have spherical symmetry.
This means that the wave function will depend only on the distance from the nucleus and not on the direction.
In any atom, the size of the s-orbital increases as the principal quantum number of the orbital increases but the geometry remains spherical.
The electron density also tends to extend further. Other orbital behave in the same way as the principal quantum number of the orbitals increases.
Which factor decided the shape of orbital?
The quantum mechanical treatment of electrons in atoms gives a clear picture of the energy levels associated with every atomic orbital which can be defined by a set of four quantum number.
Chemist find it convenient to describe the location of electron in atomic and molecules in term of this type of shape.
These representation of orbital shape are those which are said to contain 99% or 95% of the electron density of the orbital.
The value of all four quantum number influence the location of an electron, or in the terminology just introduce the distribution of electron density in space or the shape of an orbital, but the effects of the four different number are not the same.
The Principle quantum number n affects primarily the size of the orbital and has a lesser influence on its shape. The subs hell quantum number l affects primarily the shape of the orbitals. The magnetic quantum number m affects primarily the orientation of the orbital increases three dimensional space.
The spin quantum numbers has little effect upon the location of the orbitals of an isolated atom, but does have an influence on orbital interaction when the orbitals of different atoms impinge upon each other.
Why and which orbitals has the highest energy?
The energy of an electron versus it's orbital - Within a given principal energy level, electrons in p orbitals are always more energetic than those in s orbital, those in d orbital are always more energetic than those in Paris orbitals and electrons in fact orbitals are always more energetic than those in d orbital.
For example, within the fourth principal energy level, we have
4s<4p<4d<4f
In addition, the energy associated with an orbitals increases as the number of the principal energy level of the orbital increases.
For instance, the energy associated with a 3p orbital is always higher than that associated with a 2p orbital, and energy of 4d orbital is always higher than that associated with a 3d orbital. The same is true for s orbital
1s<2s<3s<4s<5s
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