The Periodic Table Chapter 6

A quest for accurate reproduction J.W. Dobereiner – published his triad classification system (ex. Cl,Br,I similar chemical properties) 1860 –Scientists agreed upon a method to measure mass –Are masses related to elemental properties? John Newlands –Noticed every 8 th element had similar properties –Law of octaves

The Law of Octaves

Dimitri Mendeleev Organized the periodic table based on increasing atomic mass Predicted the properties of unknown elements –Sc, Ge, Ga P Q 24, 25

Henry Moseley Arranged elements based on the number of protons Determined periodic law –Groups have similar properties –Properties change as you move across a period –Pattern repeats one period to the next P Q – 26, 27

Terminology Groups (Families) – (IUPAC labels 1-18) Periods Representative elements(1A – 8A) –Wide array of chemical and physical properties –Group number indicates number of valance electrons Transition elements Metalloids Metal Non metals P Q - 31

Metals Shiny, smooth Good electrical and heat conductors Malleable, ductile Solid at room temp Reactive Alkali’s and Alkaline’s (s block)

Transition Metals D and F (Inner transitional metals) block Lanthanides and Actinides P Q 33, 34, 35 – P. 182 – 48, 49, 53, 54

Non-Metals Most of p block gases or brittle solids (Br) Little luster Poor conductors Halogens very reactive Noble Gases (Inert Gases) - extremely unreactive due to filled s and p sublevels P. 181 – 28, 32

Metalloids Share properties of metals and non-metals Heavy step line – B, Si, Ge, As, Sb, Te, Po, At Found in p block P

Atomic Radius Metals - Half the distance between adjacent nuclei in a crystal of an element. Non Metals - Half the distance between bonded atoms of the same element (diatomic molecule).

Atomic Radius – Family Trends Increases Atomic charge and occupied energy levels increase. Occupied orbitals shield electrons in the outer most energy level from the pull of the nucleus.

Atomic Radius – Period Trends decreases Increasing positive charge pulls the valence electrons closer to the nucleus. Shielding does not influence this trend because the effect is constant. P Q P Q - 50

Ions – Atoms gain or lose electrons to have a complete set of valence electrons (Octet Rule) NaNa protons 10 electrons 11 protons 11 electrons Empty outer orbital or energy level makes it smaller. Electrostatic repulsion decreases. 11 p  10 e

Increased electrostatic repulsion Cl 17 Protons 17 Electrons Cl Protons 18 Electrons

Ionic Radius – Family Trends Principle energy levels increase in size.

Ionic Radius – Period Trends 3 protons 2 electrons 4 protons 2 electrons 5 protons 2 electrons 6 protons 2 electrons 7 protons 10 electrons 8 protons 10 electrons 9 protons 10 electrons Electron repulsion decrease P Q - 41, 42 - P Q P Q - 64, 65

Ionization Energy – energy needed for an atom to lose an electron Be  Be +  Be 2+  Be 3+ kilojoules/mol or kj/mol 1s 2 1s 2 1s 2 1s 1 2s 2 2s 1

1 st ionization energies increase as you move across a period due to the increased attraction of the nuclear charge. The stability of the filled sub level affects the ionization energy. P. 181 – Q - 37, 38, 40 – P. 182 – Q – 55, 58 – P. 183 – Q – 67B

Ionization Energy – Family Trends Decreases as you move down a family. The further the electron from the nucleus the easier it is to remove. P Q - 39

Electronegativity – a measure of an atom’s ability to attract an electron P Q - 43, 44, 45