Mendeleev’s Periodic Table (1869)

Periodic Law Moseley arranged the periodic table by increasing atomic number. When Elements are arranged in order of increasing atomic number, there is a periodic repetition of physical and chemical properties.

Metals, Nonmetals, and Metalloids

Squares in the Periodic Table

Representative Elements Groups 1A through 7A s and p sublevels of the highest occupied energy levels are not filled Groups include: Alkali metals Alkaline-earth metals Halogens

Noble Gases Group 8A Inert gases that rarely take part in reactions s and p sublevels are full

Transition Elements Transition metals Inner transition metals Valance electrons in s and d sublevels Inner transition metals Valance elections in s and f sublevels

Electron Configuration Energy level for d = row –1 Energy level for f = row – 2

Trends in Atomic Size Atomic radius – ½ distance between the nuclei of two atoms of the same element when the atoms are joined Size increase down a group because there are more energy levels Size decrease down a period because the positive nucleus pulls the increased negative charge of the electrons closer

Trends in Atomic Size

Ions Charged atoms Cations – have lost electrons Anions – have gained electrons Ionization Energy – is the energy required to remove an electron from an atom 1st ionization energy is the amount required to remove the first electron from an atom 2nd ionization energy is the amount required to remove an electron from a +1 ion

What does the blue line on the chart mean? (think energy levels)

Trends in Ionization Energy Ionization energy decrease down a group because the valence electrons are further from the nucleus. Ionization energy increases down a period because the nuclear charge and the charge of outer energy level increases across the period, while the shielding effect remains constant.

Trends in Ionic Size Cations are smaller than their atoms Anions are larger than their atoms.

Trends in Ionic Size

Trends in Electronegativity Electronegativity – is the ability of an atom to attract electrons in a bond Increases from left to right Decreases down a column Fluorine is the most electronegative element at 4.0

Summary of Trends