Warm-up For sulfur: 1. How many valence electrons does it have? 2. What ion does this typically form? 3. Write the electron configuration for the ion.

Warm-up For sulfur: 1. How many valence electrons does it have? 2. What ion does this typically form? 3. Write the electron configuration for the ion.

Nucleus Contains 99.9% of the mass of an atom Found at the center of the atom Diameter is only 1/10,000 of the entire atom

Protons and Neutrons Proton positively charged subatomic particle, number determines element s identity (atomic number) Neutron neutral subatomic particle Protons and neutrons have almost the same mass

Electron Negatively charged subatomic particle Electrons have almost no mass Move around the nucleus in a cloud

Changes to atoms Ions different number of protons and electrons Calculate the difference in charge Example: Chloride ion (Cl - ) has 17 protons (+) and 18 electrons (-) Cations are positively charged Anions are negatively charged Isotopes different number of protons and neutrons Add number of protons and neutrons to find the mass number of that specific isotope Example: Carbon-14 has 6 protons and 8 neutrons Atomic mass on the periodic table is an average of all of the isotopes of that element that exist *Worksheet*

History of Atomic Theory http://hi.fi.tripod.com/timeline/timeline.htm

Figure 11.17: The Bohr model of the hydrogen atom. Copyright by Houghton Mifflin Company. All rights reserved. 7

Figure 11.5: Electromagnetic radiation. Copyright by Houghton Mifflin Company. All rights reserved. 8

Figure 11.6: Photons of red and blue light. Copyright by Houghton Mifflin Company. All rights reserved. 9

Figure 11.10: An excited H atom returns to a lower energy level. Copyright by Houghton Mifflin Company. All rights reserved. 10

Figure 11.11: Colors and wavelengths of photons in the visible region. Because each element has a different electron configuration, each has a unique emission spectrum Copyright by Houghton Mifflin Company. All rights reserved. 11

Determining electron location Principle energy levels Represented by the letter n A whole number between 1 and 7 As n increases, energy increases and the electron is farther away from the nucleus Sublevel Shape of electron cloud s = spherical p = dumbbell 1st energy level has 1 sublevel -- s 2nd energy level has 2 sublevels s, p 3rd energy level has 3 sublevels -- s, p, d 4th energy level has 4 sublevels -- s, p, d, f

Determining electron location Orbitals Describes the orientation in space within a sublevel s = 1 orbital p = 3 orbitals d = 5 orbitals f = 7 orbitals

Electron Configuration Rules Aufbau Principle - electrons enter orbitals of lowest energy first. Pauli Exclusion Principle - an atomic orbital can hold a maximum of 2 electrons and those 2 electrons must have opposite spins Hund s Rule - When electrons occupy orbitals of equal energy (same sublevel), one electron enters each orbital with parallel spin before pairing oppositely.

Valence Electrons Electrons in the outermost occupied principle energy level of an atom Electrons that are NOT in the outermost principle energy level are known as core electrons

Periodic trends Atomic size/radius - Tends to increase down a column (group) - Tends to decrease across a row (period) Ionization energy - energy required to remove an electron from an individual atom (gas) Tends to decrease down a column (group) Tends to increase across a row (period) Electronegativity - tendency for an atom to attract electrons to itself when bonded to another element Tends to decrease down a column (group) Tends to increase across a row (period)

Periodic table Write principle energy level for each period (1-7) Label the representative groups (1-8) For each group list: Metal, nonmetal, or metalloid? Special name (if it has one, such as alkali metals) Number of valence electrons General valence electron configuration (s 1, s 2 p 3 ) Do the elements typically form a cation or anion? What is the usual charge on the ion?