Locating Electrons

 Newtonian Mechanics – describes objects at ordinary velocities (classical mechanics)  Quantum Mechanics – describes particles at velocities near that of light (subatomic particles)  Quanta – a packet of nrg

 It is impossible to know both the location and velocity of an electron at the same time. ◦ To see an e- we would have to bounce light off of it which would change its velocity and in turn its position.  Ex: helium-filled balloon in a dark room

 In 1926, he treated e- as waves, giving us the e- cloud model. ◦ Radial Probability of Electrons The area of highest probability forms the e- cloud.

 Principle Quantum Number (n)  Sublevel (l)  Orbital (m)  Spin (s)

 Energy levels are a particular distance from the nucleus n = # e- =

 The maximum number of electrons in each nrg level is 2n 2 ◦ At n = 1, there can be 2(1) 2 = 2 e- ◦ At n = 2, there can be 2(2) 2 = 8 e- ◦ At n = 3, there can be 2(3) 2 = 18 e-

 Tells the shape  Each nrg level has a # of sublevels = to n Energy Level (n) # SublevelsSublevels 111s 222s, 2p 333s, 3p, 3d 444s, 4p, 4d, 4f

 The 3 rd quantum number (m) tells which orbital and electron occupies.  One pair (2e-) of electrons can occupy each orbital ◦ s sublevels have 1 orbital (2e-) ◦ p sublevels have 3 orbitals (6e-) ◦ d sublevels have 5 orbitals (10e-) ◦ f sublevels have 7 orbitals (14e-)  ** each orbital can hold UP TO 2 e-**

 Indicates direction of spin of e- ◦ -1/2, +1/2 (clockwise, counterclockwise)  Pauli Exclusion Principle states that no two electrons in an atom can have the same set of 4 quantum numbers. ◦ The two e- in an orbital must have opposite spins.

 Helium has 2 electrons ◦ n = 1 ◦ l = s ◦ m = 1 ◦ s = 1 up, 1 down  Helium’s electron configuration would be: Principle Quantum # # of e- Sublevel

 Li  N  Ne  Na

 Degenerate orbitals have the same nrg

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f - Sublevels fill in order of increasing nrg - 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

 What is the electron configuration for: ◦ Cl – 17 ◦ Pb - 82

 e- first occupy the lowest possible nrg level available.  Electron Dot Notation – show only valence e-, those in the outer most nrg level ◦ ONLY UP TO 8e- ◦ 8 e- = stable  Valence electrons – e- in the highest nrg levels ◦ These e- are what form bonds

 Examples:

 Only show valence electrons  Dots are either placed 1 on each side or in pairs. ◦ Never more than 2 per side  This is why lithium has only one dot and why carbon can have 2 dot notations.

 What would the electron dot notation be for titanium?  Ti = 22e- BUT only 2 valence e-  Electron Configuration Notation  Electron Dot Notation Valence e- -d’s are NEVER valence e-, they ALWAYS fill after a high nrg level -Same for f’s

 Show all orbitals with electrons  Electrons represented as up and down arrows  Arrows must be opposite within orbitals Nitrogen (7) Fluorine (9) 1s2s 2p

 Single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals.

Principle Quantum Number SublevelOrbitals Per Sublevel Orbitals Per Energy Level e- Per Sublevel e- Per Energy Level 1s1122 2spsp spdspd spdfspdf

 Quantum Mechanical Model – describes and electron as having a particular amount of energy, depending on its location.  Electron clouds give you the highest probability of locating and electron.

 Excited state – electrons in a higher than normal energy state.  Nitrogen: 1s 2 2s 2 2p 3 (ground state) 1s 2 2s 2 2p 2 3s 1 (excited state)

 Lose or gain e- ◦ Anions – are negatively charged, having gained e- ◦ Cations – are positively charged, having lost e- ** atoms will gain or lose e- to become more stable**

 Na: 1s 2 2s 2 2p 6 3s 1  Na + : 1s 2 2s 2 2p 6 ◦ Alkali metals, like Na, want to lose their 1 valence e- to become stable.  Cl: 1s 2 2s 2 2p 6 3s 2 3p 5  Cl - : 1s 2 2s 2 2p 6 3s 2 3p 6 ◦ Halogens, like Cl, want to gain a valence electron to become stable.

 Filled and half-filled sublevels are more stable than partially filled sublevels.  This Cr takes an e- from 4s to put one e- in each of its 3d orbitals and Cu takes a 4s to fill each of its 3d orbitals  Orbitals are stable when either full or half-full 1s 2s 2p 3s 3p 4s 3d