Aufbau principle

Aufbau principle
The electrons are filed up in the empty orbitals of an atom from the lowest energy
orbital to the higher energy orbital.
Pauli exclusion principle
We have seen that three quantum numbers n, I and m are needed to defna an orbital.
Each orbital may hold up to two electrons, provided they have opposite spins.Thus
,an extra quantum number is required to defna the spin of an electron in an orbital
Thus four quantum number are needed to defne the energy of an electron in an atom. The paulis exclusion principle states that no two electrons in one atom can accomodate a maximum of to two electrons of opposite spin.

Hund’s rule

Accoriding to this rule , the degenerate orbitals ( i.e orbirals having same energy ) will be filed by one electron eachhaving same spain and then only pairing of electrons will take place . Alternatevily , the filling up of electron in in the degeneratere orbitals will take place in such a way that the multipilicy (M)value will be maximum where M is defned as follows :
MS=+21||
Where S= total spin value of all electrons in degenerate orbitals .

PERIODIC TABLE

Historically, elements with similar or related propirties were grouped togher into family of elements.for example, lithium,sodium and potassium formed the family of noble metals.Based on the systematicrealitionships among the elements,a chart known as periodic table evolved that refected systematic trends in physical and chemical properties of elements.Periodic table is the arrangement of elements in a tabular form on the basis of their properties that facilitates the systematic study of properties of elements.
Genesis of periodic classification .The early attempts at classificatoin of elements were based known at that time .Dobereiners triad in 1869 ,German chemist Dobereiner was able to indenfity several groups of theere elements that showed similarity in physical and chemical properties.He observed that in the set of three elements having having similar properties ,the atomic weight of the middle elements of is the arithmetic mean of the atomic weights of other two elements
In the periodic table,so constructed ,the elements in the same families (e.g,lithium,sodium,potassium) were arranged in the vertical columns 1,2,3,4,5,6,7,8,.The horizantal rows were referred to as series .
Mendeleevs periodic table was later modified after the discovery of inert gases and several other elements .The inert gases were placed in new Group 0.Each long period was divedid into two series , named as odd and even depending on the serial number. The first seven elements formed the even series and the last seven elements formed the odd series.

Aubau printsipi

Elektronlar atomning bosh orbitallarida eng past energiyali orbitaldan yuqori orbitalga uchadi.
Pauli istisna printsipi
Kordikki ,orbitalni aniqlash uchun uchta n,l va m kvant bolishi mumkin qarama-qarshi spinlarga ega bolishi sharti bilan ikkita elektrongacha ushlab turadi .Shunday qilib energiyani aniqlash uchun tortta kvant soni kerak boladi .Paulining istisno qilish printsipi shuni korsatadiki ,bitta atomdagi ikkita elektron bir xil qiymatga ega bololmaydi tortta kvant soni yoki pastki qavatdagi orbital maksimal ikki elektronni sigdira oladi.
Yuqoridagi qoidagi asoslanib ,har bir asosiy energiyaga joylashishi mumkin bolgan elektronlar soni darajasini kvant sonlarini almashtirish orqali hisoblash mumkin.
Hund qoidasi
Ushbu qoidaga kora degeneratsiyalangan orbitallar bitta elektron tomonidan otadi. Ularning har biri bir xil spinga ega va keyin faqat elektronlarning juftlashishi sodir boladi .Shu bilan bir qatorda yuqoriga kotarilish .Degeneratsiyalangan orbitallardagi elektron koplik (M) qiymati maksimal boladigan tarzda sodir boladi .Bu yerda M quyidagi tarzda aniqlanadi:
M S= +2 1 //
Bu yerda S=degeneratsiyalangan orbitallardagi barcha elektronlarning umumiy spin qiymati .
DAVRIY JADVAL
Tarixiy jihatdan oxshash yoki oxshash xususiyatlarga ega elementlar bolgan elemenlar oilasiga birlashtirilgan .Masalan, litiy,natriy,va kaliy faol metallar oilasini tashkil etdi mis,kumush va oltin zadogonlar oilasini tashkil qilgan metallar.Elementlar ortasidagi tizimli munosabatlarga asoslanib, davriy jadval deb nomlanuvchi diagramma paydo boldi.(elementlarning fizik-kimyoviy xossalarining tizimli tendentsiyalari) Davriy jadval – bu elemntlarning xusuyatlariga kora jadval korinishidagi joylashuvi, bu jarayonni osonlashtradi. (elementlarning xossalarini tizimli organish )Davriy tasnifning genezisi .Elementlarni tasniflshning dastlabki urinishi quyidagicha asoslanadi osha paytda malum bolgan cheklangan miqdorgadi elementlar boyicha eksperimental kuzatish .
1829 yilda nemis kimyogari Dobereyner aniqlay oldi oxshashlikni korsatgan uchta elementlarning bir nechta guruhlari fizik va kimyoviy xossalari.U buni toplamda kuzatdi .Oxshash xususiyatlarga ega bolgan uchta element triadal deb ataladi.
Davriy jadvalda shunday tuzilgan ,bir xil oiladagi elementlar masalan litiy,natriy,kaliy 1,2,3,4,5,6,7,8,guruhlar sifatida belgilangan vertikal ustunlarga joylashtirilgan vertikal ustunlarga joylashtirilgan.Garizontal qatorlar qator deb atalgan.Mendelev davriy jadvali keyinchalik inert gazlar va bir qancha boshqa elementlar kashf etilgandan keyin ozgartirildi .inert gazlar yangi guruh 0 ga joylashtirildi .Har bir uzoq davr ikkiga bolingan seriya raqamiga qarab toq va juft deb nomlanadi.Birinchi yetti elementni tashkil etdi.Juft qator va oxirgi yetti elementni tashkil etdi .