Ions

Remember: Atoms make elements Elements make compounds Everything around you is made of compounds What that compound does, depends on how the elements inside are bonded

At this point… We know an atom has +ve protons in the nucleus and –ve electrons outside the nucleus Normally the two are equal so this makes the atom neutral What would happen if the protons and electrons were not equal?

Ion A charged atom or group of atoms When we take away or add electrons to an atom, we disrupt the balance. There is now more/less e- than p+ Ions are never formed by changing the # of protons!

Positive or Negative? Lose an electron = Positive ion Lose weight = good thing Called a “cation” Cats are cute!

Positive or Negative? Gain an electron = Negative ion Gain weight = bad thing Called an “anion” Unlikable words start with “an”: analogy anaconda anarchy anchovy anger anguish animosity annihilate

Let’s look at an example Sodium – Na In group 1A, so it has one valence e- If we take that one valence e- away, the sodium atom will have “lost weight” It will be positive Na+

Another example Fluorine F If we add an e-, fluorine has “gained weight” F -

What do we call them? Cations Anions Named after the “parent” atom Na+ atom would be called a sodium ion Mg+2 atom: called a magnesium ion Al+3 atom: called an aluminum ion Anions Named by taking the root of the atom name and changing the ending to -ide Cl- atom: called chloride ion O-2 atom: called oxide ion

Ions and the Periodic Table The cation atoms match their group number in the first 3 groups Li+1 is in Group 1A Sr+2 is in Group 2A Ga+3 is in Group 3A Transition metals will form multiple positive ions depending on what they are mixing with

Metals always lose their e- so they will always have +ve ions Nonmetals always gain e- so they will always have –ve ions Group 6 atoms have a -2 charge Group 7 atoms have a -1 charge

Chemical Bonds A chemical bond is the force needed to hold two atoms together This bond can come from an attraction between a +ve nucleus and -ve e- Bond could come from attraction of positive and negative ions

Any way you look at it, a chemical bond forms because of “opposite attraction” Lets look at some examples…

Opposites Attract

Opposites Attract

Opposites Attract

Opposites Attract

Why are they attracted to each other? Valence electrons of course! Electron-dot-diagrams will help us to see this Group 1A 2A 3A 4A 5A 6A 7A 8A Diagram Li Be B C N O F Ne

What is an ionic bond? Ionic bond is the force that holds oppositely charged particles together in an ionic compound

What’s in an ionic compound? At least one cation and one anion have to be present

Talking about Ionic Compounds When saying the compound or writing it down, you have to mention the cation 1st If there are only 2 elements, we call it a binary compound

Solving Ionic Compounds # of e- lost has to = # of e- gained Na + Cl  Na+ + Cl-

Let’s look at some examples! if we add 3 Na atoms to fill all the N spots, we lose as much as we have gained Na + N  Na Na + N  Na Na3N N Na

Li + O  Li O Li Li2O

Formula unit The simplest ratio of ions in an ionic compound

Monatomic ion A one-atom ion Mg +2 Br - Cs +

Oxidation Number The charge on a monatomic ion Mg +2 charge = +2 Br - charge = -1 Cs + charge = +1 It is possible to have more than one oxidation #

Al+3, Ga+2, Ga+3, In+, In+2, Tl+, Tl+3 Oxidation Numbers Group Common Ions 3B Sc+3, Y+3, La+3 4B Ti+2, Ti+3 5B V+2, V+3 6B Cr+2, Cr+3 7B Mn+2, Mn+3, Tc+2 8B Fe+2, Fe+3 Co+2, Co+3 Ni+2, Pd+2, Pt+2, Pt+4 1B Cu+, Cu+2, Ag+, Au+, Au+3 2B Zn+2, Cd+2, Hg2+2, Hg+2 3A Al+3, Ga+2, Ga+3, In+, In+2, Tl+, Tl+3 4A Sn+2, Sn+4, Pb+2, Pb+4

Oxidation Numbers When bonding 2 atoms together, their oxidation numbers have to equal zero Na + Cl  Na+ + Cl-  NaCl

Polyatomic ions Ions made of more than one atom Even though there are more than one element involved, we still consider it as one ion You never change subscripts

Polyatomic Ions Ion Name NH4+ ammonium IO4- periodate NO2- nitrite C2H3O2- acetate NO3- nitrate H2PO4- dihydrogen phosphate HSO4- hydrogen sulfate CO3-2 carbonate OH- hydroxide SO3-2 sulfite CN- cyanide SO4-2 sulfate MnO4- permanganate S2O3-2 thiosulfate HCO3- hydrogen carbonate O2-2 peroxide ClO- hypochlorite CrO4-2 chromate ClO2- chlorite Cr2O7-2 dichromate ClO3- chlorate HPO4-2 hydrogen peroxide ClO4- perchlorate PO4-3 phosphate BrO3- bromate AsO4-3 arsenate IO3- iodate

Polyatomic Ions Sodium and Nitrate Calcium and chlorate Na+ + NO3- + ClO3-  Ca(ClO3)2

Naming Ions and Ionic Compounds When you have polyatomic ions with the same root element but different numbers of oxygen NO3- and NO2- The one with the most oxygen will be named after the root element with –ate on the end The one with the least amount of oxygen will be named after the root element with –ite on the end nitrate and nitrite

What would we call… SO4-2 and SO3-2 sulfate and sulfite

One element - 4 combos Greatest number of oxygen, named with prefix per- and suffix -ate Next in line has the suffix –ate Third in line has the suffix –ite Lastly, it has the prefix hypo- and the suffix –ite ClO4- ClO3- ClO2- ClO- perchlorate chlorate chlorite hypochlorite

Naming Ionic Compounds Name the cation 1st Monatomic cations use the element name Monatomic anions take their name from the root of the element name plus the suffix –ide If the compound has a polyatomic ion, you simply name it

Examples NaBr name the cation 1st and use the cation name Sodium Add –ide to the root of the anion Sodium bromide

Example: Cu(NO3)2 Copper can have a +1 or +2 charge, how do we know which to choose? Nitrate is only a -1 charge and there are 2 of them, so … We must be using the +2 copper Copper (II) nitrate