November 5, 2015 BELLRINGER: Why do elements bond with other elements? WHEN FINISHED WITH THE BELLRINGER: Pick up Great Combinations Packet

Goals To explain the difference between the types of bonds. To identify what bond is present in a chemical compound. To draw chemical bonds

Q: Why do atoms bond? Atoms bond because they want to have a full valence shell (outer shell) Full shell would have 8 e- in them Exception: H and He only want 2 (b/c they only have one energy level)

Q: Why do atoms bond? Atoms can either get rid of electrons (become more positive- cations) or gain electrons (become more negative- anions) Atoms can also share electrons

Q: What are the types of chemical bonds? There are 2 types of chemical bonds: ionic bonds and covalent bonds. There are also metallic bonds (between 2 metals), but we won’t talk much about those

1. Ionic Bonds (Give and Take) This type of bond is formed between IONS (positive cation and negative anion) Remember: Opposites attract In this bond, one atom gives up electrons and the other takes those electrons for itself

1. Ionic Bonds (Give and Take) NaCl (Sodium Chloride) is a perfect example Draw the Lewis diagram for Sodium.

Sodium How many valence electrons does it have? 1 (first column = first family/group) How many more does it need to be complete? 7 Is it easier for Sodium to gain those electrons or get rid of the one it has? Easier to get rid of 1, than gain 7

Sodium Sodium will give up its 1 valence electron to another element (Chlorine) Which elements want that one electron? Why? Halogens (they have 7 e- so need only 1 more)

Sodium and Chlorine

Ionic Bonds NOTICE: Electrons want to have pairs of electrons, unpaired electrons are unstable and want a partner.

What charge will these atoms have in an ionic bond? Alkali metals= +1 They will give up their one valence electron, which makes them have one more proton than electron Alkaline earth metals = +2 They will give up their 2 valence e-, which makes them have 2 more p+ than e-.

What charge will these atoms have in an ionic bond? Boron family = + 3 They will give up their 3 valence e-, which makes them have 3 more p+ than e- Carbon family = +/- 4 It is just as easy for them to gain 4 e- as it is for them to lose 4 e-, so these can go either way

What charge will these atoms have in an ionic bond? Nitrogen Family = -3 They will gain 3 e-, which makes them have 3 more e- than p+ Oxygen Family = -2 They will gain 2 e-, which makes them have 2 more e- than p+

What charge will these atoms have in an ionic bond? Halogens = -1 They will gain 1 e-, which makes them have 1 more e- than p+ Noble Gases = 0 They already have 8 e- and don’t need anymore, so their number of e- = number of p+

Ionic Bonds Ionic Bonds are not always a 1:1 ratio, you might need more than 2 atoms.

Ionic Bonds Example Calcium has 2 valence e- to give up

Ionic Bond Example A calcium atom can give it’s electrons to 2 atoms of fluorine (each fluorine has 7 valence e-) The chemical formula for this would be CaF2 which tells me I have 1 atom of calcium and 2 of fluorine

Ionic Bonds Ionic bonds form between METALS and NONMETALS Metals like to give up electrons, nonmetals like to steal them

Agenda Items Part 1 of HW pkt due tomorrow EXAMPLE: Strontium and Bromine