 Where are protons located?  nucleus  Where are e- located?  orbitals  Which has greater mass?  protons

 As you move across a period (left to right) OR down a group/family, characteristics of elements change consistently

 As you move across a period (Left to right)  Atomic number increases  As you move down a group/family  Atomic number increases

 As you move across a period (Left to right)  Average atomic mass increases  As you move down a group/family  Average atomic mass increases  Find the exceptions:  Te & I  Co & Ni  U & Np

 In trends we are more concerned with general instances than with specific details.

 All elements want to be like  Noble gases  This means they want  Stability [full valence e-: outer shell e- (s & p)] Octet rule : 8 valence e-  Electrons are mobile. For which elements does it make more sense to lose electrons than to gain electrons?  Families starting with H, Be, B – metals want to lose  Which elements are more likely to gain electrons? Why?  Families starting with N, O, F, - non metals want to gain

 Metals tend to be scatterbrained (cations) meaning they will most likely lose electrons, giving them a positive charge.  Nonmetals tend to be thieves (anions) meaning they will most likely gain electrons, giving them a negative charge.

ElementGain/Lose# of e-Noble GasCharge Calcium Fluorine Oxygen Bromine Sodium * Hydrogen * Carbon * Silicon

 Statements on Stability:  1. elements with completely full sublevels are very stable  2. elements with completely filled “p” sublevels (full valence shells) are most stable (Noble gases)  3. elements with exactly half-filled sublevels are reasonably stable. * This means that elements, while preferring completely filled sublevels, will also work to make exactly half filled sublevels.

ss pp dd ff  We will now focus on transition elements a little bit more:  Side note: As of now, I will use the terms “charge” and “oxidation state” or “oxidation number” interchangeably.

 What is atomic Radii?  Half the distance between the nuclei of identically bonded atoms. (size of atom)  Diatomic elements: H 2 O 2 N 2 Cl 2 Br 2 I 2 F 2

 What happens to the number of protons as you move down the periodic table?  increases  What happens to the energy levels of the outermost electrons?  increases  What do you think happens to the radius of an element as you move down the periodic table? Why?  Increases b/c of the nrg levels of the e-

 What happens to the number of protons as you move across the periodic table (from left to right)?  increases  What happens to the energy levels of the outermost electrons?  Stay the same  What do you think happens to the radius of an element as you move across a period from left to right? Why?  Decreases, e- moved closer to the nucleus (rubber band demo)

 Cause #1  # of protons (atomic number)  Cause #2  Nrg level (due to e- shielding) E- shielding: e- are pulled to the nucleus but the inner shell e- push out the outer shell e- (little kids soccer example)  (Cause #3)  Based on 1 & 2, atomic size

 As you move across a period from left to right, atomic radii  decreases  As you move down a group, atomic radii  increases

 Ionization Energy:  The amount of energy you have to “pay” to remove an e-  Video:  In metals, as a general rule  The lower the ionization energy (IE), the more reactive the metal  As you move down a group, ionization energy  decreases

First let’s review the three causes of all trends:  What happens to # of protons as you move across a period?  increases  What happens to e- shielding as you move across a period?  Stays the same  What happens to atomic size, as you move across a period?  Decreases (gets smaller)

 In other words you have more protons in the nucleus, the same e- shielding & smaller atoms.  Will it be easier or harder to take away electrons?  harder  As you move across a period, ionization energy  increases

 As you move across a period, ionization energy  increases  As you move down a group, ionization energy  decreases

 Electron Affinity:  The amount of nrg an atom will “pay” to get an e-  How are electron affinity and ionization energies similar?  Deal with movement of e- & energy  Same trend  How are they different?  IE is to get rid of an e-  EA is to gain an e-

 Proceeding left to right across a period, electron affinity  increases  Proceeding down a group, electron affinity  decreases  NOTABLE EXCEPTION:  Noble Gases

 Electronegativity:  The attraction an atom has for the e- in a bond (the tug-o-war in covalent bonding b/c sharing e-)  Which element wants electrons the most?  Fluorine  Which element wants electrons the least? (other than noble gases)  Francium

 Moving across a period from left to right, electronegativity  increases  Moving down a group, electronegativity  decreases

 Atomic radii: size of the atom  Trend is:  Across -> atomic radii decreases Why? Add protons = smaller atoms  Down -> atomic radii increases Why? Add nrg levels = bigger atoms  Ionization energy: nrg to get rid of e-  Trend is:  Across -> IE increases Why? Add more p+= more compact= harder to remove  Down -> IE decreases Why? More reactive = lower IE

 Electron Affinity: amount nrg to gain e-  Trend is:  Across -> EA increases  Down -> EA decreases Why? Bartering: If you want to be a noble gas= you pay  Electronegativity: attraction an atom has for e- in a bond  Trend is:  Across -> IE increases  Down -> IE decreases Why? Closer to the Noble gas = more pull you have to make a bond

ElementsLargest radiusIonization E.Electron Affin.Electronegativity Ca, Br, Ga Be, Sr, Mg F, Br, I Cs, Pb, At Si, Sn, C Rb, P, F

 Ionic Radius (size of Ions)  Cations (positive ions) are smaller than the noble gas they are like.  Why? lose e- = less e-shielding lose e- = more protons = e- pulled closer to nucleus  Anions (negative ions) are larger than the noble gas they are like.  Why? More e- = more e- shielding = further from the nucleus

 When elements are arranged in order of increasing atomic #, elements with similar chemical and physical properties appear at regular intervals.  Similar valence e - within a group result in similar chemical properties