Chemistry 11 Early models of the atom 1 Structure of the Atom Democritus Developed the idea of atom Thought things were made of atoms that have different Shapes Aristotle Matter is made of different amounts of:,,, earth fire water and air John Dalton Elements are made up of very small particles called atoms An element is made up of a group of atoms identical Atom A particular combination of specific types of compound atoms creates a chemical compound Chemical reactions involve the reshuffling of the atoms in a compound to make new compounds JJ Thomson Atoms contain A electrons positively charged Atom = a ball of matrix w/ negative electron charges ( e I distributed _ TN With plum pudding Model (Draw in the box) 0 0 5
i ' Chemistry 11 Early models of the atom 2 Earnest Rutherford 5 # 0 experiment Gold foil Most of the alpha particles (positively charged) went through the atom but some, bounced back nucleus! Atom is mostly with empty space a positively charged nucleus is! Nucleus contains almost all the mass of the atom and consists of and pt n pt n! The number of electrons surrounding the nucleus equals the number of protons in the nucleus, but electrons are much lighter than protons 1 ' Niels Bohr Electrons had specific, circular orbitals Lshell ) rather than being randomly distributed model for Be planetary e aye t Quantum Model (Erwin Schrodinger) Shri dinger showed e do not Q around, but they move around the nucleus in a random, but slightly predictable way Cloud model nucleus, ": : : ( :, I
Chemistry 11 Atomic Theory Study Guide 1 Subatomic Particles: Electrons, Protons, and Neutrons RutherfordBohr Model: Definitions: Proton: Subatomic particle in the nucleus that is tveiy charged Neutron: _ Subatomic particle in the nucleus that is neutral Electron: _ Subatomic rely charged particle Symbol Charge Mass (amu) Electron Proton Neutron Atomic Number and Mass Number Look at K for example: 19 K Potassium 39098 Atomic Number: Of an element is the # of pt of its atoms No two elements have the same atomic number This number defines an element Increases by one as you go through the periodic table (refer to periodic table) = Number of protons = Atomic # # of e (in neutral atoms) Therefore, for K: 19 protons = 19 electrons in a neutral atom
Chemistry 11 Atomic Theory Study Guide 2 So how do we fill the electrons in the shells? We follow the rule that certain shells can hold a certain number of electrons Bohr Diagram for K: 1 st shell: e 2 nd shell: e 3 rd shell: e 4 th shell: e etc We will only focus on the first 20 elements for now! Ions: Electrons can be from an atom if enough is applied to it For example, Na atom Na + sodium atom remove e sodium ion 11 protons 11 protons 11 electrons 10 electrons Ions usually form as a result of atoms having +ve charged ions have electrons, while ve charged ions have electrons Bohr Diagram for Na + : How do we find out the number of neutrons in an atom? Mass number: = atomic mass Total # of Pt and he
Chemistry 11 Atomic Theory Study Guide 3 By convention, number 39 number 19K Example using K: How many neutrons are present in an atom of K that has mass number = 39? mass number = number of protons + number of neutrons number of neutrons = = = Isotopes Not all atoms of the same element contain the same number of (remember number of protons determines the identity of elements, NOT the number of neutrons) Isotopes: Atoms having the same # of pt but not n Example: Carbon, C has three naturally occurring isotopes: C12, C13, C14 Electron Configuration Electron Configuration: A description Ot Which orbitals in an atom contain e and how e many are in each orbital 4 types of shells: s orbitals can hold e p orbitals can hold e d orbitals can hold e f orbitals can hold e
! Complete the following table: # of p + # of e # of n Atomic # (# of p + ) Mass # (# p + + n) Atomic mass Chemistry 11 Isotope Calculation Study Guide Isotope Calculation!"!"!"!! or C12!! or C13!! or C14 Why is the mass number of element different from the atomic mass? The mass number is a whole number which represents sum of # of p+ and n but atomic mass is usually a decimal number which represents the molar mass of the element Molar mass: Mass of one mole of particles eg, Molar mass of Cl is Where did this number come from? Scientific data tells us that there are two isotopes of chlorine Cl35 and Cl3 5% of the element is Cl35 and 2423% of it is Cl3!"#$%!!!"##! =!!"#$%&'(!!"!!"#$#%&!!!(!"##!#!) I eg, What is the molar mass of boron, given that there are: 188% of B10 Rest is all B11 eg, What is the molar mass of magnesium, given that there are: 899% of Mg24 1000% of Mg25 Rest is all Mg26!!