okay so let's talk about subatomic particles and the word subatomic means smaller sub below the size of an atom right so these are things that we find inside of atoms that make up the atoms themselves and there are a lot of subatomic particles but we only need to know three we need to know the protons neutrons and the electrons oh we need to know more than their name we need to know some other features so we're not know about quarks and neutrinos and all of that all atoms are made out of protons neutrons well or some don't actually have neutrons but most of them have protons neutrons and electrons all three of these but what different is a number of these guys so different types of atoms have different numbers of the so although all atoms are made out of the same subatomic particles the number of these varies from one to the next the periodic table will describe properties of atoms by describing the number of these subatomic particles so every different element has an entry we start with the lightest up here in the upper left and go across we read across so hydrogen the lightest ceiling the second lightest then we go down to the next row and the next row and what we'll start to see that in in columns these elements share certain properties that's how they organize the view guys share certain properties in cars we read left to right in terms of going up in weight and what I'm going to do is I'm going to draw one example of an entry in the periodic table to to describe to explain how to read it because you need to know Noora striction memorized a on table but we expect you to be able to interpret it and know what it means so I'm going to use the entry for sodium middle there was na up top above that with an 11 and below that is twenty two point nine nine zero and you can follow along with a copy to try out a table in your book or in your assignment task wherever you have it right so this is the entry for sodium so first of all you need to know what each of these different features represents the top number is the atomic number it is another way to say that it is the ID number all sodium will have this 11 as an ID number it's what separates sodium from if you have a 10 up here than your neon middle number is our atomic symbol right it's going to be one or two letters it's two letters the second letters lowercase and the bottom number is going to be the atomic mass number okay and we're going to go back and look at how these are late to the different numbers of protons neutrons and electrons here in a second but before I do that I want to talk about the structure of an atom and this analogy is from your book and it says if you were to take an atom and blow it up to the size of a football field most of it is going to be empty space someplace in the middle of that Adams will be something relatives in size of football field the size of a pencil eraser that is the center and we call that Center the nucleus that word nucleus move like Colonel or central and in the nucleus as where we're going to find our protons and neutrons not middle part outside of the nucleus zipping around sort of anywhere they could be and there's places where they're more likely to be so initially like they're more likely to be close to nucleus that is they get more of them they'll be further out that's all we're going to find the electrons so electrons don't orbit around the nucleus like planets around the Sun but that's sort of our simplified version so protons and neutrons are in the nucleus electrons are found outside of the nucleus