Frequency and wavelength are mathematically related to each other by the equation: c = λν.

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1 Chemistry I Unit 3: Electron Configurations and the Periodic Table Properties of Light The Wave Description of Light Electromagnetic radiation- a form of energy that exhibits wavelike behavior as it travels through space. All the forms of electromagnetic radiation form the electromagnetic spectrum. 7 Types of Electromagnetic Radiation 1. Gamma Rays 2. X- Rays 3. Ultraviolet 4. Visible Light 5. Infrared Light (Infrared radiation) 6. Microwaves 7. Radio/TV waves Properties/Characteristics of Waves Wavelength (λ) is the distance between corresponding points on adjacent waves. Frequency (ν) is defined as the number of waves that pass a given point in a specific time, usually one second. Frequency and wavelength are mathematically related to each other by the equation: c = λν. Amplitude height of the wave. Crest top of the wave Trough bottom of the wave

2 J.J. Thomsen s Plum pudding" Model Atomic Models throughout History The electrons and protons are uniformly mixed throughout the atom. Rutherford s Atomic Model Atoms consisted of a diffuse cloud of negatively charged electrons surrounding a small, dense, positively charged nucleus. Bohr Model of the Hydrogen Atom Niels Bohr proposed an atom model that said the electron can circle the nucleus only in allowed paths, or orbits. The energy of the electron is higher when the electron is in orbit farther from the nucleus.

3 The Heisenberg Uncertainty Principle The Heisenberg uncertainty principle states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle. Electrons do not travel around the nucleus in neat orbits; they exist in certain regions called orbitals. Orbital- three- dimensional region around the nucleus that indicates the most likely location of an electron. Atomic Orbitals and Quantum Numbers Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals. 4 Quantum Numbers Principle quantum number- n- main energy level (values 1-7) Angular momentum quantum number- l- shape of the orbital (# of sublevels, values s, p, d, f) Magnetic quantum number- m- orbitals in the sublevels s has 1 orbital p has 3 orbitals d has 5 orbitals f has 7 orbitals The spin quantum number,s, spin of the electron (+1/2, 1/2 or up or down) Electron Configurations The arrangement of electrons in an atom is known as the atom s electron configuration. Rules Governing Electron Configurations Aufbau principle an electron occupies the lowest- energy orbital that can receive it (developed by Bohr and Pauli). Pauli exclusion principle no two electrons in the same atom can have the same set of four quantum numbers. Hund s rule- - orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin. Orbital Notation A line represents an unoccupied orbital, with the orbital s name written underneath the line. 1s

4 An orbital containing one electron is represented as: é 1s An orbital containing two electrons is represented as: é ê 1s The lines are labeled with the principle quantum number and sublevel letter: Noble- Gas Notation The Group 18 elements (He, Ne, Ar, Kr, Xe, and Rn) are called the noble gases. A noble- gas configuration refers to an outer main energy level occupied, in most cases, by eight electrons (an octet). Mendeleev and Chemical Periodicity Mendeleev arranged the elements in order of increasing atomic mass and noticed certain similarities in their chemical properties appearing at regular intervals. Repeating patterns are referred to as periodic. Mendeleev grouped elements with similar properties together a periodic table of the elements. Mendeleev placed all the known elements in his periodic table, leaving empty spaces. Moseley and the Periodic Law 1911, Henry Moseley discovered that the elements fit into patterns better when arranged by atomic number, rather than atomic weight. The Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers. The Modern Periodic Table The Periodic Table is an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group. Periods and Blocks of the Periodic Table Elements are arranged vertically in the periodic table in groups that share similar chemical properties. Elements are also organized horizontally in rows, or periods. The periodic table is divided into four blocks, the s, p, d, and f blocks.

5 Group 1 Alkali metals. Ø All are soft silvery metals Ø All very reactive with water Ø Never uncombined in nature Ø Usually form +1 ions Image Source: sciences.com/wp- content/uploads/2014/10/alkali- metals- 2.jpg. Retrieved October 24, 2014 Group 2 Alkaline- earth metals. Ø Group 2 metals are slightly less reactive than the alkali metals Ø Never uncombined in nature Ø Usually form +2 ions Image Source: table- alkaline- earth- metals.png. Retrieved October 24, 2014

6 The d- block elements metals with typical metallic properties transition elements. Ø malleable Ø ductile Ø luster Ø form + ions Image Source: files/transition- metals.jpg Retrieved October 24, 2014 Noble Metals d block metals that are highly resistant to corrosion and oxidation in air. These are usually precious metals due to their rarity in the Earth s crust. Most noble metals are also considered precious metals because they have high economic value. Ø Ruthenium (Ru) Ø Rhodium (Rh) Ø Palladium (Pd) Ø Silver (Ag) Ø Osmium (Os) Ø Iridium (Ir) Ø Platinum (Pt) Ø Gold (Au) Ø Some sources also consider Mercury (Hg) and rhenium (Re) noble metals as well. Image Source: content/uploads/2014/07/precious.png. Retrieved October 24, 2014

7 The p- block elements of Groups except helium. Ø All of the nonmetals except hydrogen and helium. Ø All six of the metalloids are also in the p block. Ø Eight p- block metals. Ø main- group elements- s- block and p- block elements together. Image Source: synthesis.com/webbook/34_qn/ptqm5.png. Retrieved October 23, 2014 Group 17 The halogens. Ø Most reactive nonmetals. Ø React with most metals to form salts. Ø Usually form - 1 ions Ø The metalloids located between nonmetals and metals in the p block (on stair- step line: B, Si, Ge, As, Sb, Te). Image Source: Retrieved October 23, 2014 Group 18- The Noble Gases

8 Ø All unreactive gases at room temperature Image Source: table- noble.gif Retrieved October 23, 2014 f- block elements Rare Earth Elements Ø Lanthanides, the first row of the f- block (4f), are shiny metals similar to the Group 2. Ø Actinides, the second row of the f- block (5f). All are radioactive. Image Source: wiki.wikispaces.com/file/view/periodictable.gif/ /385x352/periodictable.gif Retrieved October 24, 2014

9 Periodic Trends (Patterns Associated with the Periodic Table) Atomic radius is one- half the distance across an atom. Ø Atoms decrease in size across a period. Ø Atoms increase in size down a group. Image Source: Retrieved October 23, Ionization Energy Ø Ionization energies of the main- group elements increase across each period. Ø Ionization energies generally decrease down the groups. Image Source: IE.GIF Retrieved October 23, 2014

10 Ion atom or group atoms that has a positive or negative charge. Ø Ions are formed when atoms gain or lose electrons. Ø Any process that results in the formation of an ion is referred to as ionization. Ø A positive ion is known as a cation. A cation is formed by the losing one or more electrons. Ø Metals usually form + ions. Oxidation loss of electrons o Na à Na + + 1e - Image Source: chemistry- class.com/aluminium- ion.jpg. Retrieved October 23, Ø A negative ion is known as an anion. An anion is formed by the adding one or more electrons. Ø Nonmetals usually form ions. Reduction gain of electrons o F + 1e - à F - Image Source: batz.wikispaces.com/file/view/slide6%20anion%20formation.jpg/ /404x188/slide6%20anion%20formation.jpg Retrieved October 23, 2014 Ø More about ions in later units

11 Valence Electrons Ø Chemical compounds form because electrons are lost, gained, or shared between atoms. Ø The electrons that interact in this manner are those in the highest energy levels. Ø The electrons available to be lost, gained, or shared in the formation of chemical compounds are referred to as valence electrons. Image Source: Retrieved October 23, 2014 Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound. Ø Electronegativities tend to increase across periods, and decrease or remain about the same down a group. Image Source: Retrieved October 23, 2014

12 Electron Affinity the energy required to remove an electron. Metals have low electron affinities and nonmetals usually have higher electron affinities. Image Source: Electron_affinity_periodic_table.svg.png Retrieved October 23, 2014