Chapter 3: Atoms and Molecules Grade 8

Meme Moment

Scientist of the Day

Frederick McKinley Jones Adopted by a priest in 8 th grade Wanted to be a mechanic o Apprentice on a farm In WWI, learned electronics Made a transmitter for a radio station, then hired for more jobs Made a fridge that could fit on a truck (and not be plugged in!) o Changed the food in stores o Thermo King!

Scientist of the Day

Frederick Soddy Worked with Rutherford Discovered different types of radiation Nobel Prize in chemistry Started writing books about economics instead o People thought he was a crackpot, but his ideas are used today o Predicted that economy would run on fossil fuels instead of gold Was going to have an element named after him, but “Soddyium” sounds like sodium

Scientist of the Day

Ada Lovelace Lord Byron’s daughter Mother didn’t want her to be a poet, so she only learned math & logic Socialite Met Charles Babbage (inventor of computer) at a party Wrote the first computer program/algorithm Famous science writer too

Atomic Theory (AKA History) November 10, th grade Chapter 3.1

Symbols for Molecules HBrO 4 Each atom has a symbol from the periodic table Symbols can be 1 or 2 letters. First = capital, second = lower case or none Numbers say how many No number = 1

Atomic Theory Changes Sometimes science changes very quickly 1500s alchemy 1600s alchemy + chemistry 1700s chemistry 1803 atoms! 1904 subatomic particles ! 1911 it changes again! 1913 it changes again! 1926 quantum mechanics

Atoms Atom: smallest unit of matter that can still be considered an element Atomic theory uses different models of atoms to explain the trends we see Atomic theory changed as new experiments explained more and more about atoms Now we know that atoms aren’t the smallest unit of matter – we have subatomic particles too!

Dalton’s Model Dalton’s Experiments Showed: Atoms are the smallest unit of matter o You can’t get smaller according to his theory o Hard spheres Atoms of the same element are exactly alike. Different elements have different atoms Atoms can never change Compounds form when atoms combine in set ratios o Table salt would always be 1 sodium + 1 chlorine

100 Years of Dalton Democritus & Aristotle used the idea of atoms to describe the universe – Dalton used science to prove it! For 100 years or so, this is unchanging fact Then Thomson comes along in1897 and tries a new experiment... In 1904, atomic theory changes to a more detailed form o Science fixes itself! We have to revise theories when new data says we don’t have all of the facts

Thomson’s Experiment Lights up when hit by beam When electric charge was introduced, the beam bent. Opposite charges attract, so there must be a negative charge to this beam

Thomson’s Model With his experiments, Thomson discovered electrons Electrons had a negative charge if they were bent towards the positive charge Thomson’s electrons were smaller than atoms and found inside atoms Already knew atoms had a neutral charge, so there must be a positive part to balance it out “Seeds in a watermelon” or “chocolate chip cookie”

Rutherford’s Experiment

Rutherford was trying to prove Thomson’s model Wanted to show that the slightly- positive gold foil could slightly bend the path of the mostly-positive atoms – he failed Some of the particles bounced There must be something hard and positive in the center of the atom in order to bounce like that – the nucleus ! The nucleus contains protons Thomson’s model only lasts for 7 years

Bohr’s Theory Revisited an old experiment from 1800s, found new interpretation Background Info: Different elements emit light in very specific places The light is from electrons “jumping” and releasing energy Red = low energy, blue = high energy

Bohr’s Model If you only got certain colors, you could only be using certain energies, so electrons needed to be in certain places – orbits Was Rutherford’s student – changes his model in 2 years “Rings on a tree” or “planetary orbits”

Schrodinger & the Cloud Model This is very simplified in your books because the math looks like this: When the math stops using numbers, it’s a problem

Schrodinger/Cloud 13 years later... Electrons aren’t in set places – they are probably in places Mapping where the electrons most likely are gives clouds around Bohr’s rings In bigger atoms, some of the clouds are more complicated than spheres

Chadwick’s Model 8 years later... James Chadwick also worked for Rutherford Heard about an experiment from Irène and Frederic Joliot-Curie o Something was knocking protons out of wax using radiation Chadwick proposes the neutron – equal mass to a proton, but uncharged

Vocabulary Nucleus: the small, heavy center of an atom where protons and neutrons are located Proton: small, positively charged particle found in the nucleus. Each element has a unique number of protons Neutron: small, neutral particle found in the nucleus. Electron: small, negatively charged particle that moves around outside the nucleus

Vocabulary Energy level: roughly energy of an electron/where an electron is located Atomic number: the number of protons. Mass number: the number of protons + neutrons. This is often different from the atomic mass shown on the periodic table (which is an average of the mass numbers for different isotopes) Isotope: atom with the same number of protons, but different number of neutrons compared to other atoms of the same element. E.g. Carbon-13 vs Carbon-12

Atoms November 3, 2015 (It’s complicated) 6 th grade – th grade – review 8 th grade – 3.1

We are all stardust. Energy Matter Gray area Made in stars Ideas E=mc 2

Studying Matter Chemistry: the study of matter and how it changes o Ms. B is a chemist! Changes and qualities in matter are classified as physical properties or chemical properties Physical properties: things that happen to a substance without turning it into another substance Chemical properties: things that happen to a substance when its turning into another substance

Substances Substance (pure substance): a type of matter that is only made up of one type of thing Mixture: combination of 2 or more substances Homogeneous mixture: cannot easily be separated – it all looks the same Heterogeneous mixture: easy to separate pieces

Atoms Atom: Smallest unit of matter. o Except not really, because atoms are made up of ‘subatomic particles’ Substances made of one type of atom are called elements. There are only 118 known elements in the universe o You can see them all on the periodic table (which is a little out of date) o Each atom has a symbol. E.g. Oxygen is O. All of them (except hydrogen and helium) were made in stars

Molecules Molecule: 2 or more atoms stuck together to make a substance (chemical). The atoms are joined with chemical bonds Chemical bond: force of attraction between 2 atoms

Molecules, cont. A single type of molecule is still a substance In some cases, a molecule can also be an element o (Carbon) C is an element/atom, but it’s also a molecule because it can exist on its own in pencil graphite, diamonds, etc o Elements like oxygen, nitrogen, hydrogen pair up with each other naturally to make diatomic molecules like O 2, N 2, H 2 When a molecule turns into another molecule, it is a chemical change or chemical reaction

Chemical vs Physical If you burn propane in oxygen, you make carbon dioxide and water vapor. o Propane, oxygen, carbon dioxide, and water are all different molecules, so you know they’ve had a chemical change What are some physical properties ? What are some chemical properties ?

Compounds November 9, th grade Chapter 3.2

Atoms Atom: Smallest unit of matter. o Except not really, because atoms are made up of ‘subatomic particles’ Substances made of one type of atom are called elements. There are only 118 known elements in the universe o You can see them all on the periodic table (which is a little out of date) o Each atom has a symbol. E.g. Oxygen is O. All of them (except hydrogen and helium) were made in stars

Molecules Molecule: 2 or more atoms stuck together to make a substance (chemical). The atoms are joined with chemical bonds Chemical bond: force of attraction between 2 atoms

Symbols for Molecules HBrO 4 Each atom has a symbol from the periodic table Symbols can be 1 or 2 letters. First = capital, second = lower case or none Numbers say how many No number = 1

Symbols – Distributive Property Al(OH) 3

Symbols – Organic Molecules Sometimes the atoms of the same type aren’t grouped together This tells chemists how the molecule is shaped/what it probably does. E.g. COOH is acidic CH 3 COOH

Practice! How many/what type of atoms do these molecules have? H 2 O CuBr 2 HgCl 2 NaCl KNO 3 (NH 4 ) 2 CO 3 CH 3 CH 2 OH

Isotopes December 8, th grade –

Isotopes Isotope: the same element with the same number of protons, but a different number of neutrons Different # of neutrons = different mass number Mass number = # protons + # neutrons Isotopes are identified by their mass number Might have different radioactivity Written as C-14 or carbon-14 or 14 C

Periodic Table December 14, th grade Chapter

Periodic Table

Developed by Mendeleev in 1869 o Holes in the table predicted “missing” elements that were soon found Organized by increasing atomic number + shared chemical properties o Originally based on atomic mass, but that doesn’t always work (look at tellurium and iodine) Can be colored differently based on what trends people want to show

Periodic Table, cont. Periodic Table: arrangement of elements showing shared & repeated properties Period: a row in the periodic table Group: a column in the periodic table. Elements in the same group share chemical properties. Also called a “family”

Groups Groups can be named 1-10, 1-8, 1-18, with letters, Roman numerals, etc depending on the book. Location is more important Groups (columns) have shared chemical properties Also called a family

Alkali Metals Very first column, minus hydrogen Very reactive: never found on their own in nature because they’ll explode on contact with air or water and instantly form something else Low density, low melting point, very soft E.g. sodium in table salt

Alkali Earth Metals “Alkaline earth metals” Less reactive than alkali metals Rarely found on their own: usually in compounds E.g. calcium in bones, limestone

Transition Metals More than one group “Normal” metals Less reactive than alkali or alkali earth metals Debate over whether La and Ac should be included E.g. silver, gold, iron, copper

Lanthanides & Actinides Bit that’s usually drawn underneath the periodic table o It’s actually more like a bubble coming out of La and Ac, but this is easier to fit on paper Debate over whether they should be lumped with transition metals Dense, radioactive E.g. uranium in reactors, americium in smoke detectors

Lanthanides & Actinides Transuranium elements: manmade elements that don’t exist in nature on earth

Halogens Counterpart to alkali metals: very reactive nonmetals Gas at room temperature (except Br) Never exist on their own in nature – so reactive that they instantly react with themselves or other elements Diatomic molecules: two atoms like F 2 or Br 2 E.g. chlorine in a pool or table salt

Noble Gases Nonmetal gases Very unreactive – for the longest time, people thought they would never react with anything E.g. helium cooling, argon in the atmosphere

Diatomic Molecules

Other Groups Funny names like “pnictogens” (N, P, As, Sb, Bi) Book calls them mixed groups – no one says this Hydrogen is special – it’s a category of its own o Makes up most of the universe

Metals Which of these is a chemical property? Luster Malleability Ductility Electrical conductivity Thermal conductivity Reactivity (especially corrosion ) Usually want to give away electrons in molecules

Nonmetals Share few properties with metals Poor conductors Dull Brittle Usually gases or solids at room temperature (bromine the only exception) Right side of the periodic table Usually want to gain or share electrons when they form molecules

Metalloids Zigzag area of many periodic tables Share properties with metals and nonmetals Solid at room temperature Good semiconductors : conduct electricity under some conditions, but not others

Frankenlecture October 28, 2015 (This was just for fun.)

What do these have in common? Ada Lovelace Chemistry Pee Frankenstein Frog legs Ozymandias Lord Byron Batteries Mary Shelley

The Book Dr. Frankenstein uses modern (for the time) science to turn dead parts into a living body o Electricity as the élan vital His monster is scary It ends badly Extra scary at the time because this might be real science o 30 years before, Luigi Galvani made dead frogs move with electricity

Élan Vital/Vis Vitalis The spark of life! (Vital force) At the time (not now): People thought organic chemistry was totally different from inorganic chemistry Organic things like animals, fur, pee, dirt were different from rocks, metals, etc Organic things had (or had touched) the spark of life – the élan vital! Inorganic could never become organic Galvani and Volta’s new batteries seemed to change that o Frankenstein seems like logical progression

Friedrich Wöhler His experiments failed, but he found something better Was trying to help support Berzelius’ theory, ended up refuting it Made urea (pee), which was impossible Organic compounds from inorganic stuff Changed science!