Warm-up Calculate the frequency of green light with a wavelength of 530 x m. What is the energy of a 8.42 x Hz wave? March 2 nd, 2015

Period Trends

Periodic Table - Review  Russian, Dmitri Mendeleev  When he arranged elements by atomic mass, he found similar properties at certain levels  Published first periodic table in 1869  Left empty spaces where he predicted undiscovered elements should be Noble gases didn’t exist

Mendeleev’s PT

Periodic Table  1911, Henry Moseley (English) found that the pattern worked best if arranged by number of protons  Our current periodic tables use this method of arrangement  Properties of elements change in a predictable way : trend  Groups : Columns (up and down)  Periods : Rows (left and right)

Trend #1 – Atomic Radius  The atomic radius of an element is a measure of the size of its atoms.  Typically the distance from the nucleus to the edge of the electron cloud  However, boundary is not well-defined

Radius increases as you move down a group. Radius decreases as you move from left-to-right across a period.

Which atom has a larger radius?  Na or Cs? Hint* Who’s closer to Francium?  Na or S?  S or O? Hint* Who’s lower in the group?

Cations and Anions  Remember that an ion is an atom with a charge.  An Anion is an atom with a negative charge Anions form when valence electrons are added to the outer energy level.  A Cation is an atom with a positive charge. Cations form when valence electrons are removed from the outer energy level.

Trend #2 Ionic Radii  An atom gets bigger when electrons are added.  An atom gets smaller when electrons are removed.

Ionic Radius increases as you move down a group. Ionic Radius decreases as you move from left-to-right across a period.

Trend #3 – Ionization Energy  An electron can be removed from an atom if enough energy is used  Ionization energy – the energy required to remove one electron from a gaseous neutral atom

Ionization Energy, cont.  Metals freely give their valence electron(s) “costs” less energy  Non-metals hold onto electrons more strongly “must pay” more energy to get rid of electrons

Ionization energy increases from left-to-right across a period Ionization energy increases moving up a group

Which has higher IE?  Li or F? Hint* which is the non-metal?  K or S?  Ba or Li? Hint* which holds onto its electrons more? ○ Which has its valence electrons closer to the nucleus?

Trend #4 - Electronegativity  Applies when an atom is in a compound NOT alone  Electronegativity – measure of how strongly an atom attracts electrons when it is in a compound How much of a bully is that element when in the compound ○ Atoms “little kids” ○ Electrons “the toys”  Fluorine (the most electronegative element – “biggest bully”) is assigned a 4.0 and then all the others were determined by comparison

Electronegativity decreases as you move down a group Electronegativity increases from left-to-right across a period

Which has higher electronegativity?  Sr or Be? Hint* Which is higher up and therefore closer to Fluorine?  P or O?  Si or Cl?

Notebook Go back through the notes and draw all of the trends that we discussed onto your periodic table in your notebook. Use map pencils and markers to help differentiate the different trends.

Content & Language Objectives Warm-Up Periodic Trends HW: None March 2 nd, 2015

Warm-up 1. Choose the atom in each pair that has the largest atomic radius. a) Al F b) Sr O c) Br I 2. Circle the atom in each pair that has the greater ionization energy. d) Rb Be e) Na Cs f) Cl Sn March 3 rd, 2015

Content & Language Objectives Warm-Up Periodic Trends Worksheet HW: Finish Worksheet March 3 rd, 2015