Glencoe Chapter 6 Bryce Wolzen

 Dmitri Mendeleev: ◦ Developed the first “modern” periodic table (1869) ◦ Arranged elements according to increasing atomic mass ◦ Predicted places for as yet undiscovered elements ◦ There were exceptions to this arrangement

 Henry Moseley: ◦ Arranged the elements in order of increasing atomic number. ◦ This resulted in clear periodic pattern of properties.  Periodic Law:  There is a periodic repetition of chemical and physical properties (called periodicity) when elements are arranged by increasing atomic number.

 Arranged in order of increasing atomic number  Columns are called families or groups ◦ Elements in a family have similar chemical properties ◦ Also have same number of valence electrons ◦ Coincidence? (No!!)  Rows are called periods or series o All elements of a period have the same number of energy levels.

s-block p-block d-block f-block

1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 4p 5p 6p 7p 3p 2p 1s 4f 5f

 1. Representative elements:  Are in groups 1, 2, and  Identified by the numbers  of electrons in their  "s" and/or "p" sublevels.  Periodic properties are best illustrated by these elements.

 2. Transition Elements:  Are in groups  Identified by the numbers of electrons in their “d" sublevels.

 3. Inner Transition Elements:  Identified by the numbers of electrons in their “f" sublevels.

 Outer-shell (valence) electrons will always be filling "s" and/or "p" sublevels  Therefore, there can be a maximum of 8 valence electrons  Atoms with filled outer-shells are very stable, the least reactive, or inert. ◦ This is called the octet rule  Elements tend to gain or lose electrons to attain an octet  Atoms with 1 or 7 valence electrons are the most reactive

Metals Metalloids Nonmetals

 1. Metals: ◦ Shiny ◦ Solids at room temperature ◦ Good conductors of heat and electricity ◦ Malleable ◦ Ductile  Alkali metals: (Group 1) ◦ Most reactive metal family ◦ Electron configuration ends ◦ in s 1 (one valence electron)

 1. Metals (continued):  Alkaline earth metals: (Group 2) ◦ Second most reactive metal family ◦ Electron configuration ends in s 2 ◦ two valence electrons  2. Metalloids: ◦ Physical and chemical properties of both metals and nonmetals

 3. Nonmetals: ◦ solids or gases at room temperature ◦ Poor conductors of heat and electricity ◦ Dull and brittle  Halogens: ◦ Group 17 ◦ Most reactive nonmetal family ◦ Electron configuration ends in s 2 p 5 (7 valence electrons)  Noble Gases: ◦ Group 18 ◦ Least reactive of all chemical ◦ families ◦ Electron configuration ends in s 2 p 6 (8 valence electrons-an octet)

 Atomic radius:  measure of the size of an atom  typical distance from the nucleus to the boundary of the surrounding electrons.  Increases down a group  Adding a new energy level  Decreases across a series  Adding electrons to an existing energy level, which increases the nuclear attraction

 Atomic Radius

 Ionic Radius:  Measure of the size of an ion  Ion: ◦ A charged particle ◦ Neutral atoms gain or lose electrons to acquire a charge  Cation: a positively charged ion ◦ Formed by metals ◦ Have lost electron(s) ◦ Smaller than the corresponding atom because the loss of valence electrons results in the loss of an entire energy level

 Ionic Radius (continued):  Anion: a negatively charged ion ◦ Formed by nonmetals ◦ Have gained electron(s) ◦ Larger than the corresponding atom  (the number of protons has not changed; therefore, the attraction between the nucleus and the increased number of electrons is weaker).

 Ionization Energy:  The energy required to remove an electron from an atom  Decreases down a group ◦ Outer electrons are further from the nucleus and easier to remove  Increases across a series ◦ As atomic radius decreases across a series, each successive electron is closer to the nucleus and harder to remove (the nuclear attraction is greater – so IE increases.

 Ionization Energy:  Metals have lower ionization energies than nonmetals ◦ Easier for them to reach an octet by losing 1-3 electrons rather than gaining 5-7 electrons  Nonmetals have higher ionization energies than metals ◦ Easier for them to reach an octet by gaining 1-3 electrons rather than losing 5-7 electrons

 Electron affinity is the change in energy of a neutral atom when an electron is added to the atom to form an anion.  In other words, it’s the neutral atom's likelihood of gaining an electron.  The greater the energy drop, the greater the stability of the ion to it’s neutral atom.  Increases across a period and decreases down a family.

 Electronegativity:  Measure of the ability of an atom in a compound to attract electrons  Decreases down a group ◦ As radius increases, electrons are further from the bonding atom’s nucleus; therefore, harder to exert attraction for them  Increases across a series ◦ As radius decreases, electrons are closer to the bonding atom’s nucleus ; therefore, easier to exert attraction for them

 Electronegativity:  Metals have low electronegativity values-they form cations ◦ Easier for them to reach an octet by losing electrons rather than gaining them  Nonmetals have high electronegativity values- they form anions  Easier for them to reach an octet by gaining electrons rather than losing them

 Electronegativity