hello AP biology students we're going to go over the second section of unit one and in this section we're going to go over chemical bonds chemical bonds are attraction forces between atoms and there are many different types of chemical bonds but in this section we're going to really focus on ionic and Cove valent bonds when talking about chemical bonds we have to discuss something called veence electrons these are the electrons that are found in the furthest orbital away from the nucleus of an atom as you can see we have our atom and the veence electrons are going to be these electrons in the outermost orbital of that atom typically when atoms interact and form a chemical bond these veence electrons are going to be the determining Factor when looking at the properties of the chemical bond and the properties of the atoms to determine the number of veence electrons you're going to be looking at the group number on the periodic table for instance all of the atoms or all of the elements in this First Column here are going to have one veence electron then two then three four 5 6 7 and 8 we skip all of these Metals here because they don't follow a nice pattern and they do have a certain number of valence electrons but these are the ones that we really only deal with with Biology remember that helium has two and it's on this side typically it should be over here but it has a filled orbital with only two now when looking at these valence electrons atoms can have up to eight veence electrons and atoms want to have eight veence electrons or in other words they want to have filled orbitals now atoms can gain or lose electrons to complete this role so in other words electrons can be given or shared to fill the octet rule one thing that I like my students to understand about these atoms and valence electrons is how to draw a Le Dot Structure basically all this consists of is the element symbol and the number of veence electrons represented by dots in the diagram above here you can see that the x is going to represent the element symbol if an element only has one veence electron you can see we're going to put it to the right here if it has two veence electrons we're going to put one here and one here you can see three we put one here here here and then four they all go around once and then so on and so forth now there are exceptions to these rules for instance helium only has two veence electrons but they're actually going to be paired together here but this is a basic framework of how to produce these Le dot structures now whenever we see a line between these atoms this line represents a chemical bond as you can see here we have nitrogen here with five veence electrons and hydrogen with one veence electron each whenever these electrons and atoms chemically interact they are going to form bonds between the atoms and as you can can see here the line between the nitrogen and hydrogen's are going to represent two electrons interacting with each other to form a chemical bond now there can be a single double and triple bond depending on the interaction of the electrons you can see the hydrogens form a single Bond here the oxygen forming a double bond and these nitrogens forming a triple bond remember that each line represents one chemical bond and each line represents two electrons so between the two oxygens we have four electrons and between the two nitrogens we have six electrons since it's representing a triple bond and a double bond typically when chemical bonds are formed when electrons are shared these are called Cove valent bonds again we can see our two atoms here sharing two electrons and filling its orbital this is an example of a calent bond where electrons are going to be shared between two atoms you can see the electrons in red flying around the orbitals of the two hydrogen atoms I always like showing this meme you have a joke about calent bonds do share our other main type of chemical bond is going to be an ionic bond and this is when atoms are going to give or take creating a Charged ion so in this case sodium has one electron and chlorine has seven what's going to happen is sodium is going to lose an electron and give it to chlorine this fills the octet rule for both sodium and chloride and what happens is sodium will become positive and chlorine will become negative the reason behind that is because since sodium lost an electron it lost a negative charge making it positive and since chlorine gained an electron it became more negative since the electrons have a negative charge we refer to positively charged ions as being a cation while negatively charge ions are called anion this is an example of ionic bond where an electron from sodium is going to be given to the Florine atom here making the sodium positive and the Florine negative what happens then is since there is a positive and negative charge there is an attraction between those two charges creating a ionic bond I always find this style of meme just hilarious you can see the electron leaving the sodium atom and glor chloride