Electrons in Atoms: Electron Configuration Chemistry EQs: What is the relationship between matter and energy? How does the behavior of electrons affect the chemistry of atoms?

SC3 Students will use the modern atomic theory to explain the characteristics of atoms. b. Use the orbital configuration of neutral atoms to explain its effect on the atom’s chemical properties. f. Relate light emission and the movement of electrons to element identification. GPS

Vocabulary Aufbau Principle Pauli Exclusion Principle Hund’s Rule Electron Configuration Valance Electron Energy levels Lewis Structure Ground state Excited state Orbitals Quantum Vocabulary

Excited Electrons

Bohr’s Model: electrons orbit the nucleus; only orbits in certain energies are permitted. Ground State- lowest E level Excited State- Higher than ground state. The e- are raised to the next level, then release light when they return to ground state Must have enough E to raise to next level or won’t happen. Niels Bohr, a young Danish physicist working in Rutherford’s lab, proposed a quantum model for the hydrogen atom that correctly predicted the frequencies of the lines in hydrogen’s AES. *Bohr’s model demonstrated that a hydrogen atom has certain Energy states that are allowed; where the orbits represent the energy levels. An atom with excess energy is said to be in an excited state. The lowest possible energy state of an atom is called its ground state. Bohr Model of the Atom:

Bohr Model

Bohr Model of the atom

DeBroglie- Quantum Mechanics- light behaves as wave & particles Visible objects (baseball) have  too small to see, need very small object to detect   Heisenburg Uncertainty Principle- Can’t know the position & speed of electron at the same time Electrons

Bohr Model  Quantum Model E- do not fall towards nucleus E- reside in electron clouds called orbitals

Energy levels- region around nucleus where e- likely to be found (electron density is high) Quantum- amount of energy for e- to jump levels Continuous- ramp, no units Quantitized- fixed levels, fixed units Electrons

Schrodinger- estimates the probability of e- to be in certain area; electrons are like a fuzzy cloud, but more dense= more likely to find e- 90% of the time in a particular location Orbitals-Wave functions with corresponding densities (shape and energy) **orbital is NOT the same as Bohr’s orbit

Electron configuration Row=Period=Energy Level => horizontal Column= Group/ Family=> vertical Elements in the same family have the same # of valence electrons & share similar chemical properties. Valence electrons= e- in to last energy level. Valence e- correspond w/ group # (does not include transition elements): Group 1A= 1 valence e- Group 2A= 2 valence e- Group 3A (13) = 3 valence e- Group 4A (14) = 4 valence e- Group 5A (15) = 5 valence e- Group 6A (16) = 6 valence e- Group 7A (17) = 7 valence e- Group 8A (18) = 8 valence e-  FULL SET; STABLE

Electron Configuration Tells the arrangement of electrons around the nucleus of an atom Written in ground state, which is the lowest energy & most stable arrangement e- arrange from lowest to highest E level

Electron configuration . Orbital: the 3-D space around the nucleus that describes an electrons probable location. Energy Level (n): indicate the relative sizes & energies of atomic orbitals. As n increases, the orbitals become larger, and the e- spends more time farther from the nucleus. n = major energy levels; n = 1-7; correspond w/ the 7 rows on the P.T. Sublevel: energy levels contained w/in a energy level; s, p, d, f Electron configuration .

Electron Configuration

What shape are the orbitals? s and p Orbitals What shape are the orbitals?

Electron Configuration Tells the arrangement of electrons around the nucleus of an atom Written in ground state, which is the lowest energy & most stable arrangement Follows 3 rules: Aufbau Principle Pauli Exclusion Principle Hund’s Rule

Each electron will occupy the lowest available energy level 1st, then higher energy levels. Aufbau Principle

Pauli Exclusion Principle A maximum of 2 electrons with opposite spins can fit in an orbital (No more than 2 e- can occupy orbitals). e- in the same orbital must have opposite spin (repulsion); Show each orbital w/ its own box One is spinning clockwise & the other is counter clockwise, Show this with one arrow going up & one pointing down. NOT   

Hund’s Rule Single electrons with the same spin must occupy each equal energy level before additional electrons with opposite spins can be added e- enter orbitals singularly, then pair up Example: when filling the p sublevel with 4e-, each box gets 1 before doubling up one box NOT   

Electron Configuration-   Using the PT: The principal quantum number , n = period. There are 4 blocks: (s, p, d, f) Noble gases:full s & p level making them inert (stable). Alkali Metals- s1 Alkaline Earth Metals- s2 Transition Elements- d1-d10 Inner Transition Elements- f1-f14 Electron Configuration-

Electron Fill Sequence

Electron Configuration

Electron Sequence Model Follow the yellow brick road 1s 2s 3s 4s 5s 6s 7p 6p 5p 4p 3p 2p 6d 5d 4d 3d 4f 5f 7s Electron Sequence Model

Electron Configuration Examples: F 1s22s22p5 Cl 1s22s22p63s23p5 Al 1s22s22p63s23p1 Br 1s22s22p63s23p64s23d104p5 Electron Configuration

Orbital Diagrams” Uses boxes to represent orbitals   1s 2s 2p 3s 3p 4s 3d 4p   1s 2s 2p 3s 3p 4s 3d 4p   1s 2s 2p 3s 3p 4s 3d 4p   1s 2s 2p 3s 3p 4s 3d 4p Orbital Diagrams” Uses boxes to represent orbitals

Noble Gas Notation Simplified version of writing e- configurations Noble gas is placed in brackets [ ]

When doing configurations for large numbers of electrons, we can take a short cut using noble gases. (yay!) Example, lets try Sulfur: (16 electrons) The noble gas that comes before Sulfur is: Neon Noble gas is placed in brackets [ ] Place noble gas in bracket to represent the e- configuration up to that noble gas. Write the rest of the e- config. for that element. So we could shortcut by writing: [Ne] 3s2 3p4 Now you try: Manganese and Strontium Noble Gas Shortcut

Electron Configuration and Orbital Notation

e- in the outer most energy level that determines chemical properties Lithium = 1s2 2s1 Bromine = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 Aluminum = [Ne] 3s2 3p1 Family Number VE are the electrons available to form chemical bonds w/ other elements. Valence Electrons

Lewis Dot Structure: Electron Dot Chemical symbol & valence electrons of atom Valuable in showing how atoms share electrons in covalent bonds We can draw Lewis structures for every element using valence electrons Count the # of valence electron, then arrange then around the symbol for the atom one at a time; up to 8 electrons. Arrange 1/ side around the symbol, then couple up if more than 4 electrons.

Lewis Dot