Electrons & Atoms

Quantum Mechanical Model Electrons: probabilities vs. points of matter The probability of finding an electron within a space can be represented by a fuzzy cloud. These shapes are where scientists believe the electrons will stay 90% of the time.

ENERGY LEVELS The model designates energy levels of electrons by principal quantum numbers. Each quantum number refers to a major or principal energy level in the atom (n=1,2,3,4..)

ENERGY SUBLEVELS Within each principal energy level, the electrons occupy energy sublevels. (They are not ORBITS because the electron is not confined to a fixed circular path.) Because electrons within the sublevels occupy specific cloud-shaped regions, the cloud shapes are called atomic orbitals. The atomic orbitals are denoted by letters (s, p, d, f, . . . .)

QM Electron Structure Principal Energy Level # of Sub-Levels Sublevels (# orbitals within a given sublevel) # of Electrons in Principal Energy Level (n=1) 1 s(1) 1x2=2 2n2=2 (n=2) 2 s(1), p(3) (1+3)x2=8 2n2=8 (n=3) 3 s(1), p(3), d(5) (1+3+5)x2=18 2n2=18 (n=4) 4 s(1), p(3), d(5), f(7) (1+3+5+7)x2=32 2n2=32

Key Things to Remember At most, only __ electrons exist in any single orbital. An orbital within a higher energy level is larger than the same type of orbital for a lower energy level (i.e. the 3s orbital is larger than the 2s orbital which is larger than the 1s orbital). Electrons in _____ energy levels are further from the nucleus. The principal quantum number (energy level) = # sublevels within that principal energy level.

d Orbitals http://www.uky.edu/~holler/html/orbitals_2.html

f Orbitals http://www.uky.edu/~holler/html/orbitals_2.html

Electron Energy and Orbitals In general, electrons in orbitals for higher levels have more energy. Orbital energy by type: f > d > p > s However, as the atom gets larger (# or electrons increases), there is some overlap between orbitals and principal energy levels.