2 Nucleus: made up of protons and neutrons in center of atom Structure of an AtomSubatomic particles: 3 particles that make up an atom (protons, neutrons, electrons)Nucleus: made up of protons and neutrons in center of atomProton: positively charged particleNeutron: particle with no charge
3 Structure of an AtomElectrons: negatively charged particles around the nucleusAll protons are alike, all neutrons are alike, and all electrons are alike even in different substances!
4 Greek Model: original idea of matter made of particles Atomic ModelsGreek Model: original idea of matter made of particlesAtomos:“not to be cut”or indivisible
5 Atomic Models John Dalton Model: 1803 All elements (gold, silver, hydrogen, oxygen,…) are made of atoms
6 Atomic Theory and Models Dalton thought that atoms were like smooth, hard spheres that could not be broken into smaller pieces.
7 Atomic Models Dalton Model: Atoms of the same element are exactly alikeAtoms of different elements are different
8 Atomic Models Dalton Model: Compounds: formed by the joining of atoms of 2 or more elements
9 J.J. Thomson and his cathode ray experiment 1897
10 Atomic Theory and Models Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.Also known as the “plum pudding” model
12 Most of the particles went directly through the foil!
13 Atomic Theory and Models Rutherford was surprised that only a few positive particles were deflected strongly. This led him to conclude that atoms had positively charged particles in the nucleus.
14 Atomic Theory and Models Since many particles passed right through the foil sheet, he also concluded that the atom must have a lot of space separating the nucleus from the electrons.
15 Atomic Theory and Models Through the early twentieth century, atomic models continued to change.Niels Bohr Model: 1912Niels Bohr suggested that electrons move in specific orbits around the nucleus of an atom
16 Atomic Theory and Models Cloud Model: 1927Electrons move rapidly in every direction around the nucleus
17 Atomic Theory and Models Modern Atomic Model:The nucleus, which contains both protons and neutrons, is surrounded by a cloudlike region of electrons.
18 Let's see what Tim and Moby have to say about Atomic Models
19 Design of periodic table Periodic Table: A classification system for elementsAtomic number79Au chemical symbolGoldcommon nameAtomic mass
20 Characteristics of Atoms Atomic Number: number of protons in each elementHydrogen = Helium = 2Oxygen = Nitrogen = ___Look at periodic table of elements in your agenda or on the back cover of your book
21 Characteristics of Atoms AMU: special unit to measure the mass of atomsOne proton = one AMUOne neutron = one AMU gElectrons have no massg
22 Using your periodic table, answer the following. How many protons does Krypton have?a) 84 b) 36 c) 83 d) 48How many electrons does Krypton have?a) 84 b) 36 c) 83 d) 48How many neutrons does Krypton have?a) 84 b) 36 c) 83 d) 48
23 Using your periodic table, answer the following. How many protons does Silver have?a) 107 b)61 c) 108 d)47How many electrons does Silver have?a) 107 b)61 c) 108 d)47How many neutrons does Silver have?a) 107 b)61 c) 108 d)47
24 Electrons Each electron is in an energy level The higher the energy level = the farther the distance from the nucleusInside level holds 2 electronsThe 2nd level holds 8 electronsThe 3rd level holds 8 electrons (it CAN hold 18)The number of electrons in the outer “shell” or “orbit” determines how it will act and react to other substances
25 Drawing Bohr Models of the Atom Remember the Bohr Model?Even though the “Cloud” model is the most accurate, we cannot diagram atoms easily in 3-D.We use Bohr’s model to illustrate which energy levels the electrons are located in.
26 Examples of Bohr Diagrams SodiumWhich element?Build a Bohr Diagram
28 Atom Game Each person represents a subatomic particle: Proton = Red Neutron = BlueElectron = YellowIn your group, please construct the following atoms – help each other!- Oxygen – O Sodium - Na- Silicon – Si Beryllium – Be- Chromium – Cr Titanium - Ti
30 Valence Electrons and Bonding Valence electrons are those electrons that have the highest energy level and are held most loosely.All elements are most stable when there are 8 electrons in their valence shellThe number of valence electrons in an atom determines which elements it can bond with.
31 IsotopesAtoms of the same element have the same number of protons but have different numbers of neutronsExample of isotopes:Hydrogen: