Science Starter Na, Ag, Br, Se, Ne, He, Cs, Hg Of the elements above, which elements are: Metals Metalloids Nonmetals Good conductors of heat and electricity Semiconductors Liquids at room temperature

Objective SWBAT describe the properties and why they occur of the major groups of the Periodic Table SWBAT identify the “blocks” of the periodic table, as per the quantum mechanical model

AGENDA Science Starter Classifying the Elements Bohr Model/Valence Electrons Intro to Quantum Mechanic Model Exit Ticket

Announcements Unit 2 Quiz Monday 2/15

Unit 2: The Electron Classifying the Elements February 8, 2016

Unit 2: The Electron February 9, 2016 Classifying the Elements

Classifying the Elements (just take notes for now, you will label these a little later…) Group 1: Alkali Metals Highly reactive, soft solids Group 2: Alkaline Earth Metals Groups 3-12: Transition Metals Group 17: Halogens Group 18: Noble Gases Stable and unreactive May have to be saved until Tuesday?

VIDEO: ALKALI METALS Bananas are a great source of ________. Alkali metals… http://www.youtube.com/watch?v=JAPWCJEo9Iw …and how they react… http://www.youtube.com/watch?v=m55kgyApYrY

ALKALINE EARTH METALS Ca + O2  CaO What do you need to keep your bones healthy? Ca + O2  CaO Stupid things people do… http://www.youtube.com/watch?v=rogZBXNqaMo

VIDEO: HALOGEN GROUP What chemical goes in pools? http://www.youtube.com/watch?v=PfDPVHMIL8c

VIDEO: NOBLE GASES What are colorful lit signs made out of? http://www.youtube.com/watch?v=jdzBRmLsUM8

CONSENSUS Elements in the same group have similar chemical properties Elements on the far right (the Noble gases) are the least reactive Elements on the far left (the alkali metals) are the most reactive.

Elements are sorted into groups or families (vertical columns) based on their chemical properties … but what determines these chemical properties?

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A VERY Brief History… When do you think the very first idea of “the atom” was suggested? https://www.youtube.com/watch?v=xazQRcSCRaY

DEMOCRITUS 460 – 370 B.C. First model of an atom!

PLUM PUDDING MODEL

ERNEST RUTHERFORD 1871-1937 Nucleus Theory 1910 alpha particle gold foil experiment An atom’s mass is mostly in the nucleus The nucleus has a positive charge (Moseley) Electrons in fixed orbit

RUTHERFORD MODEL (Jimmy Neutron Style…)

NIELS BOHR 1885-1962 Planetary Model 1913 “Thought” experiment Nucleus surrounded by orbiting electrons at different energy levels Electrons have definite orbits “Thought” experiment

BOHR’S MODEL

So what is the… BOHR MODEL?? A scientist, Niels Bohr received the Nobel Prize for discovering that electrons are not just randomly surrounding the nucleus. The Bohr Model says that electrons exist is very specific energy levels surrounding the nucleus. Electrons ONLY exist at these levels, not in between. We call these levels “SHELLS”

Let’s take a look.

ELECTRONS The chemical properties of ALL elements are determined by their VALENCE ELECTRONS. Valence Electron: electrons on the outermost energy level.

How to Calculate Valence Electrons What did we say was true about elements in the same group? They behave the same chemically!! This is all because of their VALENCE ELECTRONS! Elements in the same group have the same number of valence electrons! Pull out your periodic tables!

Group 1 (alkali metals) have 1 valence electron

Group 2 (alkaline earth metals) have 2 valence electrons

Group 13 elements have 3 valence electrons

Group 14 elements have 4 valence electrons

Group 15 elements have 5 valence electrons

Group 16 elements have 6 valence electrons

Group 17 (halogens) have 7 valence electrons

Group 18 (Noble gases) have 8 valence electrons, except helium, which has only 2

Transition metals (“d” block) have 1 or 2 valence electrons

Lanthanides and actinides (“f” block) have 1 or 2 valence electrons

VALENCE ELECTRONS 1 8 2 3 4 5 6 7 1 or 2 1 or 2

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Evidence for the Bohr model Bohr showed that hydrogen energy levels existed as steps, not continuous. Atomic motion has properties of waves. Electrons can act as waves=light=energy. We have the start of a model that relates energy and matter. Only works for hydrogen Fails for multi-electrons atoms because it doesn’t consider electron-electron interactions Charged particles in motion gives off energy Bohr model violates the law of conservation of energy Problems with the Bohr Model

Ernst SCHRÖDINGER and Werner HEISENBURG Quantum Mechanical Model 1926 Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed Electrons are particles and waves at the same time Developed quantum numbers based on theories of Einstein and Planck

ORBITALS

Quantum Mechanical Model of the Atom Experiments later showed that electrons could be treated as waves just as light energy could be treated as particles The quantum mechanical model treats electrons as waves and uses wave mathematics to calculate probability of finding the electron in a particular region in the atom Schrödinger Wave Equation can only be solved for simple systems, but approximated for others 13

Quantum Mechanical Model – the probability of finding an electron Orbit is a circular path Orbital is a probability map

Orbital Shapes: the probability an electron will be found

D orbitals