The Periodic Table of Elements

Periodic  Periodic Law  Periodic Table Something periodic occurs at regular or at least generally predictable intervals Periodic law - physical and chemical properties of the elements are periodic functions of their atomic numbers Periodic Table of Elements – a table of the elements, arranged by atomic number, that shows the patterns in their properties; based on the periodic law Can you think of anything that is periodic?

Element A pure substance made up of one kind of atom that cannot be broken down into simpler substances by physical or chemical means 92 occur naturally on earth 25 were synthesized (made) by scientists

Dmitri Mendeleev In the 1860’s he devised a periodic table where the elements were ordered by their atomic masses He did this by grouping elements together according to their similarities Image taken from:

Why do you think there are question marks here? Image taken from: Mendeleev’s Published Periodic Table of Elements

Mendeleev’s Predictions Although Mendeleev’s Periodic Table of Elements had missing elements or “gaps,” he was able to predict the characteristics of these missing elements because of Periodic Law. Date Predicted 1871Date Discovered 1886 Atomic Mass72Atomic Mass72.6 Density5.5 g/cm 3 Density5.47 g/cm 3 Bonding Power 4 4 ColorDark GrayColorGrayish White “Ekasilicon”Germanium Notice how Mendeleev’s predictions (orange column) were very accurate when compared to Germanium’s actual characteristics (green column)

Henry Moseley In 1914, his work led to a revision of the periodic table by rearranging the elements by their atomic numbers. He concluded that the number of protons in an atom is its atomic number. Image taken from:

3 Classes of Elements ClassColor Metal Non-Metal Metalloid Using this as a guide, color code your periodic table to show the three classes. Start by highlighting the “zig-zag.”

Metals Location Found on the left of the zigzag line/staircase on the periodic table (exception  Hydrogen) Physical Properties ductile, good conductors of heat and electricity, malleable, shiny, most are room temperature What metal is not a room temperature? Image taken from: lement-Photo-Gallery.--98/Sodium.htm 11 Na Au

Metals: Atoms with Few Valence electrons making them highly reactive. Notice: only 1 electron in outer level Notice: only 2 electrons in outer level Na Be Valence electron – electron(s) in the outermost shell.

Non-Metals Location Most found to the right of the zigzag line/staircase on the periodic table Physical Properties not ductile not malleable, not shiny, poor conductors, most are solid, but some are gas at room temperature Image taken from: Image taken from: 16 S Cl

Non-Metals: Atoms with more valence electrons making them less reactive. Notice: 7 electrons in outer level – almost full Notice: 2 electrons in outer level – FULL Notice: 6 electrons in outer level – almost full F O He 4.003

Metalloids Location Border the zigzag line/staircase on the periodic table Physical Properties have properties of both metals and non-metals Semi-conductors Image taken from: Image taken from: 5 B Si

Metalloids: Atoms with about ½ Full Outer Energy Level allowing them to share properties of both metals and non-metals. Notice: only 3 electrons in outer level Notice: only 4 electrons in outer level B Si

Important Features of the Periodic Table: Period (Row) each horizontal row of elements on the periodic table FROM LEFT TO RIGHT OR RIGHT TO LEFT How many periods (rows) are on the Periodic Table Of Elements?

Period (Row) Properties Seven periods on a periodic table (numbered from the top down) All atoms of the elements in the same period have the same number of energy levels / clouds –Example Period 1 = 1 cloud Period 2 = 2 cloud Period 3 = 3 cloud Etc…

Examples of Period (Row) elements having the same number of energy levels in their atoms In what period (row) do you think these atoms reside? In what period (row) do you think these atoms reside?

each column of elements on the periodic table Important Features of the Periodic Table: Group FROM TOP TO BOTTOM OR BOTTOM TO THE TOP How many groups (families) are on the Periodic Table Of Elements?

Group Properties Eighteen groups on the periodic table (numbered from left to right) Atoms of elements in the same group have the same number of electrons in the outer energy levels of their atoms (known as valence electrons) –Exceptions: Transition elements (3-12) Helium (actually has 2 valence electrons) Elements in groups usually have similar physical and chemical properties

Examples of Group Elements with the same # of valence electrons 87 Fr (223) 55 Cs Rb K Na Li H How many electrons do each of these atoms have in their outer orbital/level? What group (family) do these elements reside in?

Group Names Alkali Metals Alkaline Earth Metals Transition Metals Boron Group Carbon Group Nitrogen Group Oxygen Group Halogens Noble Gases

Periodic Trends Valence electrons increase from left to right and are the same for the entire group. Electrons shells increase from top to bottom and are the same for the entire period. Atomic mass and number increases left to right and top to bottom. Atomic radius decreases left to right due to the increase in nuclear charge pulling the electrons closer to the nucleus. However, the radius increases from top to bottom because increasing electron clouds reduce attraction of nuclear charge.

Video Clip (3 min.)

Identify the Element Period 2 – Group 14  Carbon - C Period 5 – Group 2  Strontium - Sr Group 17 – Period 6  Astatine - At Group 4 – Period 7  Rutherfordium - Rf