Chemistry Revision Material

Topics: The Periodic Table The first 20 elements (name and symbol) Metals/Non-Metals/Metalloids/Noble Gases Groups/Periods Atomic Number and Atomic Mass (You don’t need to remember the atomic mass of elements, just know what this number tells us about a particular element!) Atomic Structure Sub atomic particles – Protons (positively Charged), Neutrons (No charge) and Electrons (Negatively Charged) Protons and Neutrons are located in the nucleus of the atom while electrons constantly orbit the nucleus on pathways called ‘Shells’ Shell capacities (1st Shell 2 Electrons, 2nd Shell 8 electrons, 3rd Shell 8 Electrons) Mixtures, Elements, Compounds and Molecules Distinguish between the 4. Matter States of matter Changes of states (Evaporation, Condensation, Freezing, Melting and Sublimation) Physical and Chemical Changes

Topics cont.. Reactions Worded Chemical Equations Reactants and Products Indicators of chemical change Acids and Bases Properties and Uses of common Acids and Bases Indicators pH scale

The Periodic Table Elements can be grouped according to properties. There are 92 naturally occurring elements. Elements are substances made up of only one type of atom. The periodic table organises the elements in a particular way. A great deal of information about an element can be gathered from its position in the period table. Atomic Number Elements on the periodic table are arranged by atomic number. The atomic number of an element tells us how many protons that element has in its nucleus! Mass Number This number is the atomic weight of the element. The atomic mass tells us how many protons & neutrons there are in the nucleus of the element. As Hydrogen in the example has 1 Proton and a mass of 1 there must be 0 Neutrons in this element!

Example.. The image on the right is a section from the Periodic table. The element highlighted is Boron. Have a Go! Using the information in the diagram determine how many protons, neutrons and electrons the element Boron has. Round the mass to the nearest whole number! Remember: Elements as they appear on the Periodic Table have the same number of Protons and Electrons. Boron Protons . Neutrons . Electrons .

Metals, Non-Metals and Metaloids Elements that are classified as Metals are: Good conductors of heat and electricity. All Metals are solid at room temperature except for Mercury! Metals are shiny. Metals are ductile (Can be bent). Metals are malleable (can be pounded into thin sheets). Elements that are classified as Non-Metals are: Insulators, that is poor conductors of heat and electricity. Not ductile or malleable. Solid non-metals are brittle and break easily. They are dull. Many non-metals are gases. Elements that are classified as Metalliod: Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than non-metals but not as well as metals. They are ductile and malleable.

Groups and Periods of the Periodic Table Elements of the Periodic Table are further classified into Vertical Groups and Horizontal Periods. Group 1 included Li (Lithium), Na (Sodium) all the way down to Fr (Francium), You will notice in the diagram group 0, group 0 elements (Also known as Group 8) are called Noble Gases, these elements are inert (Non- reactive) elements. They are very stable due to their electrons! Elements in the same group have the same number of electrons in their outer most shell!! Group 1 = 1 Electron in their outer most shell Group 2 = 2 Electrons in their outer most shell, and so on!

Groups and Periods of the Periodic Table The horizontal rows are called Periods. For example: Lithium (Li) is located on the Periodic Table at Group 1 Period 2 Elements in the same Period have the same number of Electron Shells!

Atomic Structure As you know, elements are substances that are made up of only 1 type of atom. For example pure gold is made up of only gold atoms! What do gold atoms look like? All atoms consist of 3 Sub Atomic Particles Protons, Neutrons and electrons Atoms vary according to the amount of each sub-atomic particles they possess. All atoms have a nucleus (a core) and an electron cloud surrounding it. Protons and Neutrons are only found in the nucleus of an atom!

Atomic Structure cont.. Because we know how to interpret the Periodic Table, drawing the atomic structure of any of the first 20 elements is easy! Lets look at Sodium (Na). Sodium has an Atomic Number of 11 (Therefore it has 11 Protons and 11 Electrons) Sodium has an Atomic Mass of 23 (When rounded to the nearest whole number) If a sodium atom has a mass of 23 and 11 Protons there must be 12 Neutrons to have a total mass of 23 (Remember electrons are so small they don’t add any weight to an atom!) So, Sodium 11 Protons, 12 neutrons and 11 Electrons… we are now almost ready to draw this atom! One last detail to remember, electrons orbit the nucleus of an atom on shells. Each shell can only accommodate a specific number of electrons. When one shell fills up the next outer shell begins to fill! Shell 1: 2 Electrons Max – Shell 2: 8 Electrons Max – Shell 3: 8 Electrons Max! Now have a go at drawing a Sodium Atom!

Sodium Did your drawing look like this?

Atomic Structure cont.. Ready for a challenge? Under each name draw the following element: Chlorine Argon Potassium

Did they look like this? Chlorine Argon Potassium

Mixtures, Elements, Compounds and Molecules Anything that is made up of only one type of atom is known as an Element Compounds A compound is a substance made of two or more different kinds of elements chemically combined. Molecules A molecules is formed when two or more atoms join together chemically. For example Hydrogen Gas is a molecule it is formed by two Hydrogen atoms joining chemically. Whats the difference between a Compound and a Molecule? A molecule is formed when two or more atoms join together chemically A compound is a is a type of molecule with two or more different elements Mixtures A Mixture is made from two or more substances either elements, compounds or both that are not chemically joined.

Mixtures, Elements, Compounds and Molecules Classify each of the four images as a Mixture, compound, molecule or element.

States of Matter

Chemical and Physical Changes Physical changes can occur when a substance changes its physical properties however retains its chemical composition. A change of state is an example of a physical change. Water vapour, Ice and water liquid are all water in different states. Physical changes can be reversed! Chemical Change A chemical change occurs when a chemical reaction produces new chemical products. When we reacted Magnesium with Oxygen, Magnesium Oxide compound was formed. This is an example of a chemical change as new chemicals were produced. Chemical Changes are difficult to reverse

Chemical and Physical Changes Can you classify the following as chemical or physical changes? Frying an egg? Water in a puddle evaporating? Reacting Hydrochloric acid and Magnesium to produce Magnesium Chloride and Hydrogen gas? Some signs that a chemical change has occurred are: Colour change Odour Vapour Precipitate

Reactions Chemical reactions can be written using worded chemical equations. They describe what chemicals were used in the reaction (Reactants) and what chemicals are produced (Products). A worded equation looks like: Magnesium + Oxygen Magnesium Oxide In the above example Magnesium and Oxygen are the Reactants and Magnesium Oxide is the Product. Chemical equations can also be written using symbols Mg + O2 MgO (We use O2 because Oxygen gas exists as a O2 molecule)

Acids and Bases Substances with a pH of less that 7 are said to be acidic Substances with a pH greater than 7 are said to be Basic Substances with a pH of 7 are Neutral If an acid and a base of the same strength react together they will neutralise each other!

pH Scale

Revision Questions.. What is a group on the periodic table and what do elements in the same group have in common? What is a period on the periodic table and what do elements in the same period have in common? Name 3 metals, non-metals and metaloids Using your knowlegde of the periodic table name an element that is a metal and a liquid at room temperature How do compounds differ from elements? Classify each of the following as a chemical or physicl change Water freezing to form snow A cake cooking Lighting the gas on a stove Petrol evaporating at the petrol pump Lighting a match Steam condensing on the bathroom mirror Melting gold to cast gold bars Frying an egg for breakfast.