Electrons and the Periodic Table Cartoon courtesy of NearingZero.net

The periodic table is the most important tool in the chemist’s toolbox!

How the Elements Were Won Your Guide to the History of the Periodic Table and the Periodic Law

1829 Johann Dobereiner Model of triads -classified some elements into groups of three or triads. -elements in a triad had similar chemical and physical properties. (ex. Cl, Br, I and Ca, Sr, Ba) Model of triads 1780 - 1849

1868 Dmitri Mendeleev “Father of the Periodic Table” Arranged known elements in order of increasing atomic mass Noticed that similar properties repeated in regular intervals

Mendeleev’s Original Table How is it different from the one we use today?

Mendeleev and Periodic Solitaire Where gaps occurred, Mendeleev predicted the existence of new elements and their properties Mendeleev was right – three of the elements he predicted were discovered in his lifetime

1913 Henry Moseley He rearranged the elements in order of increasing atomic number to fix Mendeleev’s mistakes. 1887 - 1915

Henry Moseley His research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting in Gallipoli by a sniper’s bullet, at the age of 28. Because of this loss, the British government later restricted its scientists to noncombatant duties during WWII.

1944 Glenn T. Seaborg co-discovering 10 new elements, - moved the Actinide series out of the main body of the periodic table to their current location 1912 - 1999

Glenn T. Seaborg He is the only person to have an element named after him while still alive. "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize." Watch Island of Stability YT Vid

Modern Periodic Table still arranged by increasing atomic number This establishes the Periodic law When the elements are arranged in order of increasing atomic #, there is a periodic repetition of their physical & chemical properties

Stowe Periodic Table 7th

A Spiral Periodic Table

“Mayan” Periodic Table

Ch 6.2 – Classifying the Elements

On your copy of the periodic table label the following: Periods Groups Metals Nonmetals Metalloids Alkali metals Alkali Earth Metals Halogens Noble Gases Representative elements Transition metals Inner transition metals

The horizontal rows of the periodic table are called PERIODS.

The elements in any group of the periodic table have similar physical and chemical properties! The vertical columns of the periodic table are called GROUPS, or FAMILIES.

Metals, Nonmetals, and Metalloids Types of Elements Metals, Nonmetals, and Metalloids

Periodic Table: Metallic arrangement Layout of the Periodic Table: Metals vs. nonmetals Nonmetals Metals

Properties of Metals Good conductors of heat and electricity (sea of mobile e-) Malleable Ductile High mp Have luster Reactivity increases as move down a column. Tend to lose electrons to form cations (+)

Examples of Metals Potassium, K reacts with water and must be stored in kerosene Copper, Cu, is a relatively soft metal, and a very good electrical conductor. Zinc, Zn, is more stable than potassium Mercury, Hg, is the only metal that exists as a liquid at room temperature

Alkali Metals Group 1A (excluding hydrogen) 1 valence electron readily forms +1 cation [(+) ion] React violently with water Too reactive to be found in nature in pure Form.

Alkaline Earth Metals Group 2A Ca, Ba, and Sr react with water 2 valence electrons Readily form +2 cation Too reactive to be found in nature in pure form

Transition metals Good conductors of electricity Ions responsible for colors in solutions and gem stones Also, they are not very reactive. What would we do if gold (Au) was reactive?

Most Reactive Metal Easier to lose e- The farther it is from Nucleus (shielding)

Properties of Nonmetals Carbon (the graphite in “pencil lead”) is a great example of a nonmetallic element. Poor conductors Tend to be brittle Many are gases at room temp. Low mp dull Gain e- to become anions (-)

Examples of Nonmetals Microspheres of phosphorus, P, a reactive nonmetal Sulfur, S, was once known as “brimstone” Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

Halogens 7A or 17 Highly reactive group Most are gases 7 valence electrons from -1 anion [(-) ion]

Most Reactive Non Metal Easier to gain e- The closer it is to Nucleus

Noble Gases Group 8A or 18 Most stable group Full outer energy level Stable Octect Not completely inert Xe actually can react

Properties of Metalloids Metalloids straddle the border between metals and nonmetals on the periodic table. Have properties of both metals and nonmetals More brittle than metals, less brittle than most nonmetallic solids Semiconductors of electricity Some metalloids possess metallic luster

Silicon, Si – A Metalloid Has metallic luster Brittle like a nonmetal Semiconductor of electricity Other metalloids include: Boron, B Germanium, Ge Arsenic, As Antimony, Sb Tellurium, Te

Periodic Trends

Periodic Properties Perodicity = properties repeat in predictable patterns An element’s properties directly related to the number of valence electrons

Atomic Radii Atomic Radii Is always measured under the same conditions for each atom. Is always half the distance between the nuclei of identical atoms bonded together. If this is chlorine what is its radius? Chlorine Nucleus Atomic Radius = ? Chlorine Nucleus Distance between nuclei = 198pm

Atomic Radius Do you predict the size of the atoms will increase or decrease as you move right across a period?

Why do patterns appear? The # of energy levels remains the same The # of valence e- increases The # of protons in the nucleus increases resulting in greater effective nuclear charge (greater magnetic pull on the valence e-) Trends Across a Period

Number of energy levels increases The elements have the same number of valence e- in the same type of orbital The valence e- are further from the nucleus and don’t feel it’s pull as much due to shielding by internal e-. Trends Down a Family

Atomic Radius Down a family: atoms get larger ( more energy levels) Across a period: left to right atoms get smaller due to more protons (protons pull shells closer)

Electronegativity Linus Pauling (American chemist) devised a scale to measure electronegativity Electronegativity – tendency of an atom in a compound to attract electrons “Selfishness” F- most electronegative element arbitrarily assigned a value of 4 Values for the other elements-calculated in relation to this value

Periodic Table of Electronegativities

Ionization Energy Ionization energy (potential) Energy needed to remove one of an atom’s e-s. If the e-s are held strongly the atom will have a high ionization energy Therefore, nonmetals whose valence e- are close to nucleus have highest IE.

Size of Ions (penny demo) Cations, (+) ions = lose electrons SMALLER than original atom Anions, (-) ions = gain electrons LARGER than original atom

Octet Rule Outer Shell of 8 makes an atom “feel” great! (Chemical stability!) Octet Rule: atoms tend to gain, lose, or share electrons in order to acquire 8 valence electrons

Ions Elements in a group tend to form ions of the same charge Modeled by electron configurations [Ar] 4s K: Loses 1 electron [Ar] 4s Wants a full set of e- (like a noble gas) K +1

O: [He] [He] Ions -2 O 2s2 2p4 Gains 2 electrons Wants a complete set (like a noble gas) [He] O -2

Ionic Charges/Oxidation #s 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 +1 +2 +3 +/- 4 -3 -2 -1 + 3 + 3 or + 4 tend to have more than one option