Chemistry Spaced Learning Trilogy

C1 This atom is from an element in group 4. The mass of this atom is 12.

Li 3 7 C1 The atomic number tells you how many electrons the atom has. The mass number tells you how many particles are in the nucleus of the atom. Particle Location Relative Mass Relative Charge Proton Nucleus 1 +1 Neutron Electron Shells -1

Atoms and Isotopes Mass Number Atomic Number An isotope of an element has the same number of electrons and protons but a different number of neutrons. C1

The periodic table contains all the known elements. The columns are numbered groups. All the elements in a group have similar properties. 1 2 3 4 5 6 7 The group number of an element tells you how many electrons are in its outer shell.

Early Periodic Table What did John Newlands do? Arranged in order of atomic mass. Nowadays we know about protons so we arrange in order of ____________. The outer shell electrons determine the ______number and the chemical properties. Law of octaves: every 8th was similar atomic number Didn’t leave gaps for new elements! What did Dmitri Mendeleev do? group Put them in order of atomic mass. Arranged into groups with similar properties. C1 Left gaps for new elements and correctly predicted their properties!

Why are alkali metals so reactive? Let’s look at Potassium: Inner shell electrons shield the positive pull Reaction with water Metal + Water …………………...+………………… Electronic configuration: __________ 2,8,8,1 Metal hydroxide hydrogen A lone electron? Odd one out. This electron is far from the _________ pull of the nucleus and very _____ to remove. positive C1 easy

F Cl Br I Liquid Solid The Halogens (group 7) Group 0 Gas Moving down the group: Melting point _________, boiling point ________and reactivity____________. the noble gases are very……………….. Because they have a ………………………….. Group 0 increases increases decreases F Very reactive Gas Liquid Solid Unreactive Full outer shell of electrons Cl Br I C1 A little reactive

positive negative ionic zero high solution Atoms and Ions Ions are formed when atoms gain or lose electrons. Magnesium has two electrons on its outer shell. When it forms an ion, it loses these electrons to gain a full outer shell. Metals always form ____________ ions and non-metals form _______________ ions. Oppositely charged ions attract and form ___________ bonds. The overall charge in an ionic compound is always ________ Ionic compounds have ______ boiling points and melting points. Ionic compounds conduct electricity if they are………… or in ………………… positive negative ionic Chlorine has seven electrons on its outer shell. When it forms an ion, it gains an extra electron to fill its outer shell. zero high Molten solution C2

Giant Covalent Compounds Graphite Made of _________ Each carbon atom forms ________ bonds Has ___________ electrons Has weak intermolecular forces between layers which makes it ______. Diamond Made of carbon Each carbon atom forms _______ bonds Has no delocalised electrons Has ______________ between all the carbon atoms which makes it hard. Covalent Bonds Form between non-metals when they share electrons to fill their outer shells. carbon three delocalised soft Simple covalent compounds have very low melting and boiling points because there are weak intermolecular forces between them. four Strong bonds C2

Metals and their Properties + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Metallic bonds are positive metal i___ surrounded by a sea of free-moving (d________) negative e______. Metals can conduct electrical current because the charge (e-) can f__. They conduct heat, can be bent into shape (m______) because layers can s___ over each other. ons elocalised lectrons low alleable lide C2

Pure metals aren’t as strong as alloys: Easy for metal layers to slide over each other: STRESS Mix of different size particles in alloys make it harder for chains to slide over each other: = Alloy mixture STRESS C2

More Reactions Reactions and Rates C6 Reactions that take in heat are ____________ Reactions that give out heat are ___________ This symbol means that a reaction is _________ For a reaction to happen, molecules need to collide with enough energy, called activation energy. If we give the reactants more energy, by heating, they will move faster and collide more frequently. If we increase the concentration of the reactants, there will be more frequent collisions. If we increase the surface area, of the reactants, there will be more frequent collisions. If we increase the pressure of reacting gases, there will be more frequent collisions. Endothermic Exothermic Reversible

Catalysts Catalysts s____ up the rate of chemical reactions. They do no get c_____ by the reaction and can be re-used. Catalysts lower the a_______ e____ of a reaction. peed hanged ctivation nergy

What’s in the Air? Oxygen 21% Trace Nobles Less than 1% Carbon dioxide Tiny % Nitrogen 78%

Early Atmosphere Where did it come from? Volcanoes Lots of... Carbon dioxide Water vapour Where did it come from? No/little... Oxygen A few other gases... Methane Ammonia Volcanoes

CO2 in the Atmosphere Water vapour condenses to make the oceans CO2 dissolves into the oceans Plants use CO2 for photosynthesis Water vapour condenses to make the oceans Marine animals trap CO2 as carbonates in shells which become rocks

The Atmosphere Pollution Carbon dioxide, methane and water vapour are ………….. Greenhouse gases Global warming leads to…… Melting ice caps Storms Pollution Particulates from soot cause....................... Sulfur dioxide and nitrogen oxides cause………………….. and ………………… Carbon monoxide is …………………. Global dimming Change in rainfall patterns Changes in species distribution Respiratory problems Acid rain toxic