Inorganic Chemistry: ELECTRON ARRANGEMENT in Atoms.pptx

ELECTRON ARRANGEMENT in Atoms

1. ELECTRON ARRANGEMENT in Atoms FC 103 Inorganic and Analytical Chemistry

2. Bohr’s model (Solar System Model) introduced the concept of definite energy level or orbits around the nucleus at which electrons can be exactly located. But the development of a better model made by Louie de Broglie, Erwin Schrodinger and Werner Heisenberg following the light’s theory of Albert Einstein, which is thought of as a wave can also be thought of as a particle. Bohr’s Model Proton Neutron Electron Electron Orbit

3. developed by Werner Heisenberg “We cannot know exactly the position of an electron in the atom. The wave function will only inform us of the probability of finding an electron in a particular volume of space where an electron can most likely be found. This region of space is called ORBITAL .” Uncertainty Principle

4. Energy levels (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found. Energy levels are a little like the steps of a staircase. You can stand on one step or another but not in between the steps. The same goes for electrons. They can occupy one energy level or another but not the space between energy levels. Energy Levels

5. Electrons in energy level I (also called energy level K) have the least amount of energy. As you go farther from the nucleus, electrons at higher levels have more energy, and their energy increases by a fixed, discrete amount. Electrons can jump from a lower to the next higher energy level if they absorb this amount of energy. Energy Levels F irst four energy levels of an atom

6. Energy levels cannot all hold the same number of electrons. Some energy levels can hold a maximum of two electrons, while others can have several times more. The expression describes the maximum number of electrons in any energy level. This expression uses the symbol 𝑛 for level order . Example: Energy level K=1 2 x 2 x 1 2 K = 2 electrons   Energy Levels

7. The following table shows how we can use the expression to determine the maximum number of electrons for the first four energy levels.   Energy Levels Level Symbol Level Order ( n ) Maximum No. of Electrons K 1 1 2 2 L 2 4 8 8 M 3 9 18 18 N 4 16 32 32 Level Symbol Level Order ( n ) Maximum No. of Electrons K 1 1 2 2 L 2 4 8 8 M 3 9 18 18 N 4 16 32 32

8. The figure shows the electrons of the helium atom. The helium atom electrons have the lowest possible energy state because they fill the lowest energy level (K). The electrons would have a higher energy state if either one moved to a different energy level. Energy Levels

9. The three electrons in the lithium atom make it slightly different. One of its electrons must remain at a different energy level because it has too many for energy level K. With two in energy level K and one in L, the electrons of the lithium atom are at the lowest energy states possible. Energy Levels

10. The electron configuration of an atom is the representation of the arrangement of electrons distributed among the orbital shells and subshells. Electron Configuration

11. refers to a region of space with a high probability of finding the electron. depicted as a three-dimensional region with a 95% probability of tracing an electron. Atomic Orbital

12. Atomic orbitals are of four different types: s, p, d, and f . They are commonly denoted by a combination of letters and numerals, such as 1s, 2p, 3d, 4f, etc. The number of orbitals that each subshell can accommodate depends on the values of magnetic quantum number ( ) . The value of ranges from -ℓ to +ℓ , including zero, where ‘ℓ’ stands for azimuthal quantum number .   Types of Orbitals

13. s orbitals spherical shape 1 st energy level; spherical space encircling the nucleus The size of the orbital increases with the increase in principal quantum number (n). The order of size is 1s < 2s < 3s < 4s and so on every subshell has only one s-orbital Types of Orbitals

14. p orbitals dumbbell-shaped 2 nd energy level; two lobes or ballons tied at the nucleus, giving a dumbbell shape electrons can be found in either of the two lobes value for p orbital ranges from -1 to +1, i.e., -1, 0, +1 every subshell can accommodate three p-orbital   Types of Orbitals

15. d orbitals shaped like cloverleaf 3 rd energy level; there are five d-orbitals in each subshell values are -2,-1, 0, +1, +2 the size of this orbital also increases with an increase in the principal quantum number, such as 3d < 4d < 5d and so on   Types of Orbitals

16. f orbitals more complex shapes 4 th energy level, shape of double dumbbells values ranges from -3 to +3, i.e., -3, -2, -1, 0, +1, +2, +3 (here, ℓ = 3). every subshell can accommodate seven f-orbital size of f orbital can be arranged as 4f < 5f < 6f and so on   Types of Orbitals

17. The number of types of orbitals matches the energy level: 1 st energy level = 1 orbital (s) 2 nd energy level = 2 orbitals (s and p) 3 rd energy level = 3 orbitals (s, p and d) 4 th energy level = 4 orbitals (s, p, d and f) Types of Orbitals

18. Electrons fill orbitals in a way to minimize the energy of the atom. Therefore, the electrons in an atom fill the principal energy levels in order of increasing energy (the electrons are getting farther from the nucleus). The order of levels filled looks like this: Occupation of Orbitals

19. One way to remember the order of levels : Occupation of Orbitals

20. P Pauli Exclusion Principle states that no two electrons can have the same four quantum numbers. The first three ( n, l , and ) may be the same, but the fourth quantum number must be different.   Different Principles to determine the lowest energy arrangement of the electrons:

21. P Example: Hydrogen and Helium The first three quantum numbers of an electron are n =1, l =0, =0. Only two electrons can correspond to these, which would be either =-1/2 or =+1/2. We can conclude that these four quantum numbers refer to the 1s subshell. If only one of the values are given then we would have (denoting hydrogen) if both are given, we would have (denoting helium). Visually, this is be represented as:   Different Principles to determine the lowest energy arrangement of the electrons:

22. P Aufbau Process Aufbau from the German word " aufbauen " meaning "to build“ when writing electron configurations, orbitals are built up from atom to atom when writing the electron configuration for an atom, orbitals are filled in order of increasing atomic number Different Principles to determine the lowest energy arrangement of the electrons:

23. P Example: 3 rd row elements Following the pattern across a period from B (Z=5) to Ne (Z=10), the number of electrons increases and the subshells are filled. This example focuses on the p subshell, which fills from boron to neon. Different Principles to determine the lowest energy arrangement of the electrons:

24. P Hund's Rule when assigning electrons in orbitals, each electron will first fill all the orbitals with similar energy (also referred to as degenerate) before pairing with another electron in a half-filled orbital. atoms at ground states tend to have as many unpaired electrons as possible. Different Principles to determine the lowest energy arrangement of the electrons:

25. P Example: Nitrogen (Z = 7) atom: We can clearly see that p orbitals are half-filled as there are three electrons and three p orbitals. This is because Hund's Rule states that the three electrons in the 2p subshell will fill all the empty orbitals first before filling orbitals with electrons in them.   Different Principles to determine the lowest energy arrangement of the electrons:

26. Example: Oxygen (Z = 8) atom: Oxygen has one more electron than Nitrogen and as the orbitals are all half filled the electron must pair up.   Different Principles to determine the lowest energy arrangement of the electrons:

27. Orbital Diagrams a visual way to reconstruct the electron configuration by showing each of the separate orbitals and the spins on the electrons. done by first determining the subshell ( s, p, d , or f ) then drawing in each electron according to the stated rules above. Writing Electron Configurations

28. Example: Electron configuration of Aluminum Aluminum is in the 3rd period and it has an atomic number of Z=13. Now we shall look at the orbitals it will fill:   Writing Electron Configurations

29. spdf Notation The most common way to describe electron configurations is to write distributions in the spdf notation. Although the distributions of electrons in each orbital are not as apparent as in the diagram, the total number of electrons in each energy level is described by a superscript that follows the relating energy level. Writing Electron Configurations

30. Example: Electron configuration of Yttrium Start with the straightforward problem of finding the electron configuration of the element yttrium (refer to the periodic table). The element Yttrium (symbolized Y) is a transition metal, found in the fifth period and in Group 3. In total it has 39 electrons. Its electron configuration is as follows: In this case, 2+2+6+2+6+2+10+6+2+1= 39 and Z=39, so the answer is correct. Writing Electron Configurations

31. Noble Gas Notation called the noble gas notation, in which the noble gas in the period above the element that is being analyzed is used to denote the subshells that element has filled and after which the valence electrons (electrons filling orbitals in the outer most shells) are written. this looks slightly different from spdf notation, as the reference noble gas must be indicated. Writing Electron Configurations

32. Example: Electron configuration of Vanadium Vanadium is the transition metal in the fourth period and the fifth group. The noble gas preceding it is argon ( Ar , Z=18), and knowing that vanadium has filled those orbitals before it, argon is used as the reference noble gas. To find the valance electrons that follow, subtract the atomic numbers: 23 - 18 = 5. Writing Electron Configurations