Electrons If all atoms are composed of the same fundamental building blocks, how is it that different atoms have vastly different chemically behaviors?

Structure of the atom 3 subatomic particles: proton (p + ) neutron (n 0 ) electron (e - ) Atomic number (Z) Number of electrons? Isotopes Atomic mass

What does an atom look like?

The best model – Electron Orbitals Orbital: 3-D area in space where you are 90 % likely of finding an electron. These areas are defined by a wavefunction equation. 2 electrons maximum can fit in an orbital.

Electron energies and locations are best described with math formulas called wavefunctions. When graphed, the solutions to these formulas describe “probable locations” of the electrons. These probable locations are called orbitals. sometimes called “electron clouds”

Wavefunction graphs 3-D graphs show “probability densities” for electrons in different orbitals. Quantum theory can only specify location 90% of the time.

s sublevels have spherical orbitals. p sublevels have dumb-bell orbitals. Orbital Shapes

d sublevels have clover-leaf orbitals. More Shapes

Energy Levels, Sublevels and Orbitals Each orbital is assigned to a level and a sublevel. As orbitals occupy higher energy levels, the orbital size gets bigger (so that its area is further from the nucleus) 2s

Energy Levels, Sublevels and Orbitals Energy order of first 16 sublevels: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s The energy level is represented by the number. The larger the number, the further the orbital is from the nucleus. Electrons in high-level orbitals are not tightly held to the atom, and are easily lost to other atoms. The letter represents the sublevel of the orbital, as well as the orbital shape. s sublevels have 1 orbital, p sublevels have 3, and d have 5.

When is a sublevel filled? LevelSublevels available Maximum # of electrons in level 1s2 2s, p8 3s, p, d18 4s, p, d, f32

What does an electron configuration “look like?” Sodium atoms have 11 electrons: 1s 2 2s 2 2p 6 3s 1 What would Aluminum look like? e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

Electron Configurations No need to memorize the order of levels and sublevels! Use the PT!

Are all of an atom’s electrons involved in chemical bonding? Electron configurations can be “shortened” to emphasize the valence electrons with the Noble Gas Shortcut. Ex: Magnesium: [Ne] 3s 2 Bromine: [Ar] 4s 2 3d 10 4p 5 Noble Gas Shortcut

Only the electrons located away from the nucleus are used in making a chemical bond. Valence electrons: electrons found in the highest energy level of an atom. – This level only contains s and p electrons, so 8 valence electrons maximum. Noble gas shortcut emphasizes an element’s valence electrons. Don’t forget to count s and p electrons as valence! Valence electrons

Orbital Diagrams Each box represents an orbital. Arrows represent electrons. 3 rules: Aufbau, Hund, Pauli

Predicting Charge Octet rule: Atoms gain or lose electrons to achieve a filled outer energy level of electrons. This is most often 8 electrons in the outer energy level. General rules: Atoms with 3 or fewer valence e - lose those electrons, forming a positive ion, or cation. Atoms with 5 or more valence e - gain electrons, forming a negative ion, or anion.

Positively charged ions Result from loss of valence electrons. Ex: Magnesium: [Ne] 3s 2 will lose its 2 valence electrons, to result in Mg 2+ ion. Cations achieve noble-gas or pseudo noble gas electron configuration. Named _____________ ion. insert element name Cations

Negatively charged ions Result from gain of valence electrons from another atom. Ex: Nitrogen: 1s 2 2s 2 2p 3 will gain 3 valence electrons from another atom, to result in N 3- ion. Anions achieve noble-gas electron configuration. Named ____________ -ide insert element name, dropping last syllable Anions

Primarily negatively charged ions, but there are some positive ones. They are molecules that carry a charge. The back of your PT lists the ones used in this course. Their names end in –ate or –ite for the most part. Polyatomic ions

Bohr Model Only specific energy level values are allowed. – Quantization of energy Energy is gained and lost when transitions occur. See it: Bohr/applet_files/Bohr.html Bohr/applet_files/Bohr.html