11.5-11.6
Bohr’s model of the atom
Neils Bohr-1911 received his Ph D in physics
-was convinced that an atom has small positive nucleus with electrons orbiting around it like the planets orbit the sun
-suggested that electrons could jump to a different orbit by absorbing or emitting a photon of light with exactly the correct energy content = the difference between the orbitals
-incorrect as electrons don’t move in circular paths and the line spectrum ONLY worked for hydrogen BUT paved the way for future theories
Wave mechanical model of the atom
Schrodinger-electrons may have wave and particle characteristics
-electrons move in orbitals NOT orbits
-can mathematically only predict the probability of finding an electron at a given point in space around the nucleus
-NO information about when an electron is in a given point in space or how it moves
11.7 hydrogen orbitals
Orbital-representation of the space occupied by an electron
-probability of finding an electron decreases with greater distance from the nucleus but NEVER becomes 0
-edge of orbital “fuzzy” so no defined size
-electrons spend 90% time in orbital sphere
Hydrogen energy levels
Principle energy levels-discrete energy levels labeled with integers and subdivided into sublevels
?In a hydrogen atom, an electron undergoing which of the following transitions would emit light of the shortest wavelength?
n= 5 to n=1 or from n=4 to n=1
n=5 to n=1 because greatest distance back to ground state-probably would be blue or green light-higher energy
Level 1 = sublevel (1s)
Level 2 = 2 sublevels (2s,2p)
Level 3 = 3 sublevels (3s,3p,3d)
Level 4 = 4 sublevels (4s,4p,4d,4f)
Letters tell you the shape
s=spherical
p=2 lobbed
d=more than 2 lobes
x,y,z = tells along which coordinate the two lobes lie
-shape does not tell you about electron movement
Hydrogen orbitals
-hydrogen has 1 electron but three energy levels
-at ground state, it lies in the 1s orbital but can be excited to the 2s or 2p orbital
Pauli exclusion principle
-electrons that have the same spin cannot occupy the same orbital-they must have opposite spins and an orbital can only hold two electrons
11.9-11.10
Electron configuration
-electron arrangement
-most attractive orbital to an electron in an atom is the 1s because it is closer to the positively charged nucleus
Orbital or box diagram
-orbitals are represented by boxes grouped by sublevels(s,p,d,f) with small arrows indicating electrons
-remember to use opposite spins
Valance electrons-electrons in the outermost(highest) principal energy level of an atom and are the most important electrons to a chemist because they are the one involved with bonding electrons
Core electrons-inner electrons NOT involved in bonding atoms(they exist in a a full energy level)
-atoms of elements in the same group have the same number of electrons in a given type of orbital
?How many electrons can be in the 3d sublevel?
ten
Atomic properties and periodic trend
General
-chemistry is based on observed properties of substances
-atomic theory is an attempt to help us understand how these things occur so we can better control the chemical events that are so important in our lives
-properties of elements and trends that occur in these properties help us understand observed behavior of matter
Metals vs nonmetals
-metals-lustrous, malleable, conductors (sea of electrons)
-nonmetals- opposite properties
-chemical differences between metals and nonmetals occur because metals tend to lose electrons and nonmetals tend to gain electrons from opposite charges
-not all metals act exactly alike as some metals give up electrons easier than others
Cs>Rb>K>Na>Li
-down the group electrons are given up easier as they are further from the nucleus as Cesium’s valance electrons is in group 6s
-most active metals in lower left hand corner(Cs) and most active nonmetals in upper right(F) hand corner where electrons pulled away from metals the easiest
Atomic size
-down a group as energy levels increase as electrons distance from nucleus increases size increases
-across a period electrons are in outer most energy levels are in same principle energy level but as numbers of protons increases pulling electrons into them
?Which is the smallest atom in group 6?
oxygen
Ionization energy
-the energy required to remove an electron from an individual atom in the gas phase
-metals are low as it takes little energy to remove their valance electrons
-down a group this energy decreases so lowest energy in the lower left hand corner(easier to pull off at bottom)
-nonmetals have HIGH ionization energy and so the highest is the top right hand corner(F)
?Which of the following have the highest ionization energy?
K, Si, or O
-oxygen
?How did you know?
Closest to fluorine(highest energy)