رابعا الجدول الدورى :- Atomic Number :- the - TopicsExpress

رابعا الجدول الدورى :- Atomic Number :- the number of protons found in the nucleus of an atom or No. of electrons surrounding the nucleus of an atom . Atomic weight :- the number of proton and neutrons in the nucleus of an atom Isotops :- the elements of the same number of protons but different number of neutrons . Metals They are solids at room temp except mercury Non- metals Some are solid , but many are gases , and Bromine is liquid the first scientist publish an organized periodic table was Mendeleev . * the periodic table arranged by increasing in atomic number . * Atoms with similar properties appear in groups ( vertical columns ) , they similar because they have the same number of valence electrons . * there are 18 group ( each element increase by one energy level from the previous element ) * there are 7 periods ( each elements increase by one electron from the previous element ) . (1) Atomic size ; radius : is the distance from the center of the nucleus to the “ edge “ of the electron cloud . In period : the atomic size decrease by going from left to right . لان العدد الذرى ف الدورةبيزيد فبالتالى شحنة النواه الموجبة هتزيد فيزداد جذبها للالكترونات فيقل نصف القطر ويقل الحجم الذرى In group : the atomic size increase by going from up to down . جاوبها انت واسال Why The cation is much smaller than its atom ?? Why Anions are larger than their parent atoms ?? (2) Ionization Energy :- Energy required to remove the most loosely bound electron from a gaseous atom or ion . ( KJ/mol ) هى الطاقة اللازمة لازالة ابعد الالكترونات عن النواة يعنى لو كان حجم النواة صغير فهتشد الالكترون بقوة يبقى انى ازيل الكترون هيبقى صعب فهحتاج طاقه اعلى فطاقة التأين هتزيد وده تفسير زيادة طاقة التأين ف الدورة Across aperiod from left to right , the first ionization energy increases When we go down in a group , the first ionization energy decreases . Why ?? Due to shielding effect as in groups the radius increases So, the number of shields which make the nucleus effect is negligible So, the energy needed to remove an electron decreases So, ionization energies decrease down a group Shielding effect :- is the effect where core electrons screen or shield valence electrons from the nuclear charge . تأثير حاجز ده بيحصل لما اضيف مستوى طاقة كامل بين النواة وبين ابعد الكترون عنها يعنى بحجب تأثير النواة عن الالكترون ده بستارة من الالكترونات اللى هى المستوى الكامل وطبعا دى مش هتظهر الا ف المجموعة لانى بزود مستوى كامل وانا نازل ف المجموعة لاسفل (3) Electron affinity :- The energy released when an extra electron is added to a neutral gaseous atom . الميل الالكترونى :الطاقة المنطلقة عند اضافة الكترون للذرة المفردة يعنى م الاخر الذرة دى عندها امكانية اكتساب الكترون ولا لا طب امتى تقدر تكتسب الكترون اكيد لو قوتها كبيرة يعنى لو نص قطرها صغير فتأثيرها هيكون قوى على الالكترون وتقدر تجذبه وده سبب زيادتها ف الدورة In a period : the electron affinity increase across a period . Why ? because of filling of the valence shell of the atom . In a group : the electron affinity decrease as we go down . Why ? 1. Increase the radius of the atom 2. Increase the number of energy level So, the valence electrons become farther So, it is difficult to the nucleus to attract new electron ملحوظة Nobel gases have no affinity, because they have full valence shells and by adding or taking away electron they become unstable . (4)Electronegativity :- the tendency of an atom to attract electrons to itself when combined in a compound . السالبية الكهربية هى قدرة الذرة على جذب الكترونات الرابطة هتقدر تشد الالكترون ناحيتها ولا لا In a group: electronegativity decrease . Why ? Because, Atoms have bigger radius , the positive charge of the nucleus is further away from the bonding electrons and is shielded by extra electron shells . In a period : electronegativity increase . Why ? Because the charge in the nucleus increases across a period So, the attraction for bonding electrons is greater . ثابت shielding effct م الاخر نص القطر بيقل ف الدورة والباقى كله عكسه هيزيد وا ف الدورة لانى مبزودش مستوى طاقة كامل shielding effectوف المجموعة نص القطر بيزيد والباقى كله عكسه بيقل بس ال هيزيد مع نص القطر #Catalyst #MB

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