Unit 4 The Periodic Table How is the

Unit 4: The Periodic Table How is the periodic table a useful tool?

Introduction to the Periodic Table http: //www. youtube. com/watch? v=z. GM-w. SKFBpo http: //www. youtube. com/watch? v=v 1 Tf. PDl. A 1 x. E https: //www. youtube. com/watch? v=Uy 0 m 7 jnyv 6 U 1

Johann Döbereiner- 1817 • Arranged elements into groups of three (triads) 1

John Newlands- 1864 • The “Law of Octaves” • When arranged in order of increasing atomic weight, an element showed properties similar to those of an element 8 places ahead and 8 places behind • This arrangement did not work once the noble gases were discovered (they were discovered much later because they are stable/unreactive and are not found in compounds) 1

Dmitri Mendeleev- 1869 1

Dmitri Mendeleev- 1869 • Published a table of 63 elements • Used properties to sort elements into groups • Arranged the elements in order of increasing atomic mass • Left blanks in table for undiscovered elements 1

Henry Moseley- 1913 • Arranged elements according to atomic number (modern periodic table) 1

Groups vs. Periods 1 • Groups: Vertical columns • All elements in the same group have the same number of valence electrons • Groups 1 -2 and 13 -18 are considered main group elements (also noted IA-IIA and IIIA- VIIIA) • Groups 3 -12 are also noted IIIB- IIB • Periods: Horizontal rows • All elements in the same period have the same number of occupied principle energy levels (PELs)

Types of Elements • Metals, Nonmetals, and Metalloids 1

Physical Properties of Metals • Good conductors of heat and electricity • Have luster (shiny) • All are solid at STP, except for Hg (liquid at STP) • STP stands for Standard Temperature and Pressure (Reference Table A) • Ductile: can be drawn into wires • Malleable: can be hammered into thin sheets without breaking • High melting points • High density 1

Examples of Alloys 1

What is an alloy? • Homogenous mixture composed of two or more elements, at least one of which is a metal • Properties are often superior to those of their component elements • Ex. Steel, Bronze, Brass 1

Physical Properties of Nonmetals 1 • • Most are gases at STP A few are solids at STP (ex. sulfur and phosphorus) Bromine is the only liquid non-metal at STP Look dull NM solids are poor conductors NM solids brittle and hard Have low densities Have lower melting points

Metalloids (Semi-metals) • Have some properties of metals and some properties of nonmetals • B, Si, As, Te, Ge, Sb 1

What is an ion? • A charged particle that results from the LOSS or GAIN of electrons • Positively charged cation • Negatively charged anion • Atoms gain/lose electrons in order to obtain a stable valence e- configuration like the noble gases • The Octet Rule: All other elements want a full valence shell of 8 e- like the noble gases (except for He which is stable with 2 valence e-) 1

Chemical Properties of Metals and NMs 1 • Metals tend to LOSE electrons and become positively charged ions • Non-metals tend to GAIN electrons and become negatively charged ions

• Group 1: Alkali Metals • Have one valence electron • Highly reactive with water • Lose one electron to become +1 charged ions 1

• Group 2: Alkaline Earth Metals • Have two valence electrons • Reactive with water • **Elements in Groups 1 and 2 are so reactive that they are never found alone in nature (only found in stable compounds) • Lose two electrons to become +2 charged ions 1

Transition Metals • Groups 3 -12: Transition Metals • Can have multiple oxidation states • Colored ions must be transition metals 1

Inner Transition Metals (Rare Earth Metals) • Lanthanide series: an extension of period 6 • Actinide series: an extension of period 7 1

The Halogens • Group 17 - The Halogens • Have 7 valence electrons • Gain one electron to become -1 charged ions 1

The Noble (Inert) Gases • Group 18 - Noble (Inert) Gases • Stable/ Non-reactive • Have a complete valence shell of 8 e- (except He which has 2 valence e-) 1

What is an allotrope? • Allotrope: Different forms of the same element that have different physical and chemical properties • Ex) Carbon: Coal, Graphite, Diamond, Fullerene Oxygen: O 2 and O 3 Phosphorus: Red and White 1

What trends exist within the PT? • There are trends as you go DOWN a group and ACROSS a period 1

Atomic Radius • Atomic radius: distance from the nucleus to the outermost occupied energy level n=3 n=2 n=1 1

Ionization Energy: the amount of energy it takes to remove an electron from an atom Units: k. J/mol (values are on Table S) 1

Electronegativity • Electronegativity: the ability of an atom to attract electrons toward itself (also on Table S) • Based on the Pauling Scale (0. 7 -4. 0) 1

Group Trends (based on pg. 15) As you go DOWN a group: 1) Atomic radius increases • Why? Increase in the number of occupied PELs 2) Ionization energy decreases • Why? The shielding effect • Shielding (inner) electrons reduce the pull the nucleus has for the outermost electrons, making it easier to remove an electron 3) Electronegativity decreases • Why? The shielding effect • Shielding makes it harder for the nucleus to attract electrons toward itself 1

Group Trends 4) Reactivity increases • As you go down a group, it becomes easier to lose electrons due to the increased number of shielding electrons 5) Metallic character increases • As you go down a group, it becomes easier to lose electrons, which is a property of metals. 1

Alkali Metals Reactivity https: //www. google. com/webhp? sourceid=chromeinstant&ion=1&espv=2&ie=UTF 8#q=braniac%20 alkali%20 metals 1

Period Trends (based on pg. 16) 1) Atomic radius decreases • Why? Increasing nuclear charge, due to the increasing number of protons in the nucleus, pulls ecloser 2) Ionization energy increases • Why? Increasing nuclear charge makes it harder to remove electrons 3) Electronegativity increases • Why? Increasing nuclear charge makes it easier to attract e 4) Metallic character decreases • As you go across, it becomes harder to lose electrons, which is a property of metals. 1

Other Trends: Ionic Radii • Ionic radius: the radius of an atom’s ion • Cations are always smaller than the atoms from which they form • Why? Protons > electrons…so the nucleus can pull electrons in closer 1

Other Trends: Ionic Radii • Anions are always larger than the atoms from which they form • Why? Electrons> protons…. The nucleus can’t pull the extra electrons as close together 1

Warm-Up 1) Draw the Lewis Dot diagram for the ATOM of phosphorus 2) Draw the Lewis Dot diagram for the ION of phosphorus 3) Draw the Lewis Dot diagram for the ATOM of calcium 4) Draw the Lewis Dot diagram for the ION of calcium 5) Explain WHY it is easier to remove an electron from barium in comparison to calcium. 1