Each energy level is occupied by a fixed number of electrons: The 1st energy level is occupied by a maximum of two electrons
6 The 2nd energy level is occupied by a maximum of eight electrons The 3rd energy level is occupied by a maximum of eight electrons( or eighteen electrons if available) The 4th energy level is occupied by a maximum of eight electrons( or eighteen or thirty two electrons if available) This arrangement of electrons in an atom is called electron configuration / structure. By convention the electron configuration / structure of an atom of an element can be shown in form of a diagram using either cross(x) or dot(●) to Practice examples drawing electronic configurations a)11H has - in nucleus1proton and 0 neutrons - 1 electron in the 1st energy levels thus: Nucleus Energy levels Electrons(represented by cross(x) Electronic structure of Hydrogen is thus: 1: b) 42He has - in nucleus 2 proton and 2 neutrons - 2 electron in the 1st energy levels thus: Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Helium is thus: 2: c) 73Li has - in nucleus 3 proton and 4 neutrons - 2 electron in the 1st energy levels -1 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Lithium is thus: 2:1 Kommentar [s1]:
7 d) 94Be has - in nucleus 4 proton and 5 neutrons - 2 electron in the 1st energy levels -2 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Beryllium is thus: 2:2 e) 115B has - in nucleus 5 proton and 6 neutrons - 2 electron in the 1st energy levels -3 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Boron is thus: 2:3 f) 126C has - in nucleus 6 proton and 6 neutrons - 2 electron in the 1st energy levels -4 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Carbon is thus: 2:4 g) 147N has - in nucleus 7 proton and 7 neutrons - 2 electron in the 1st energy levels -5 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x)
8 Electronic structure of Nitrogen is thus: 2:5 h) 168O has - in nucleus 8 proton and 8 neutrons - 2 electron in the 1st energy levels -6 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Oxygen is thus: 2:6 i) 199F has - in nucleus 9 proton and 10 neutrons - 2 electron in the 1st energy levels -7 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Fluorine is thus: 2:7 i) 2010Ne has - in nucleus 10 proton and 10 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels thus Nucleus Energy levels Electrons (represented by cross(x) Electronic structure of Neon is thus: 2:8 j) 2311Na has - in nucleus 11 proton and 12 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels
9 -1 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Sodium is thus: 2:8:1 k) 2412Mg has - in nucleus 12 proton and 12 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -2 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Magnesium is thus: 2:8:2 l) 2713Al has - in nucleus 13 proton and 14 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -3 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Aluminium is thus: 2:8:3 m) 2814Si has - in nucleus 14 proton and 14 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -4 electron in the 3rd energy levels thus Nucleus Energy levels
10 Electrons (represented by dot(.) Electronic structure of Silicon is thus: 2:8:4 n) 3115P has - in nucleus 14 proton and 15 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -5 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Phosphorus is thus: 2:8:5 o) 3216S has - in nucleus 16 proton and 16 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -6 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Sulphur is thus: 2:8:6 p) 3517Cl has - in nucleus 18 proton and 17 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -7 electron in the 3rd energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Chlorine is thus: 2:8:7 p) 4018Ar has - in nucleus 22 proton and 18 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -8 electron in the 3rd energy levels thus Nucleus
11 Energy levels Electrons (represented by dot(.) Electronic structure of Argon is thus: 2:8:8 q) 3919K has - in nucleus 20 proton and 19 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -8 electron in the 3rd energy levels -1 electron in the 4th energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Potassium is thus: 2:8:8:1 r) 4020Ca has - in nucleus 20 proton and 20 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels -8 electron in the 3rd energy levels -2 electron in the 4th energy levels thus Nucleus Energy levels Electrons (represented by dot(.) Electronic structure of Calcium is thus: 2:8:8:2
12 B.PERIODIC TABLE There are over 100 elements so far discovered. Scientists have tried to group them together in a periodic table. A periodic table is a horizontal and vertical arrangement of elements according to their atomic numbers.