What do I need to know? Must Recall that all substances are made of atoms Should Explain that an element is a substance made of only one sort of atom. Could Describe the location of different elements within the periodic table

The periodic table of the elements In the periodic table elements that have similar properties are found in the same vertical column or “GROUP”. These all have the same number of OUTER ELECTRONS. We call the rows in the periodic table “PERIODS” and elements are arranged in order of increasing ATOMIC NUMBER Each element has a different chemical symbol

Chemical symbols It is important that the first letter of a chemical symbol is a capital letter and the second letter (if there is one) must be lowercase eg Ca not CA. Here are some to learn. Hydrogen H Magnesium Mg Zinc Zn Lithium Li Calcium Ca Carbon C Sodium Na Iron Fe Nitrogen N Potassium K Copper Cu Oxygen O Sulphur S Chlorine Cl Neon Ne Argon Ar Lead Pb Silicon Si

What do I need to know? Must Recall that atoms of each element are represented by a chemical symbol Should Describe the composition of an atom and the properties of sub-atomic particles Could Explain that atoms of a particular element all have the same number of protons.

What do I need to know? Must Recall that atoms are made up of protons neutrons and electrons. Should Explain that atoms of an element have the same number of protons and electrons. Could Use the mass number to work out how many neutrons there are in an atom.

Definitions Atomic number – number of protons in the atom which is characteristic of the element. It is also the number of electrons in the atom. Mass number – the total number of protons + neutrons Number of neutrons can be different even for the same element. These are called ISOTOPES

What do I need to know? Must State that electrons occupy different energy levels Should Explain that electrons occupy the lowest available energy levels Could Draw the electron arrangement for an element

Numbers of electrons Successive levels hold a maximum of: 2, 8, 8, 18

Drawing diagrams We show electronic structure in circles around the atom with the lowest energy nearest the nucleus

Electrons and reactions The number of electrons in the outer shell gives an element its reactivity. For example one outer electron is VERY reactive for example Li, Na, K, Rb. A FULL shell is called a NOBLE GAS. These are VERY UNREACTIVE eg He, Ne, Ar, Kr, Xe.

Noble gases Unreactive gases with full outer shell can be used inside light bulbs because they do not react with the filament. If we used air only then the oxygen in the air would react with the filament and burn it.

Alkali metals We call the metals in group 1 the “alkali metals” They are very reactive because they all have ONE outer electron. When alkali metals react with water it is very violent. They are more reactive as you go down the group.

What do I need to know? Must State that when elements react their atoms join with other atoms to form compounds Should Describe how bonding involves giving, taking or sharing electrons. Could Explain that compounds involving metals and non-metals involve ionic bonding and compounds of only non-metals involve covalent bonding.

Why bond? Chemical elements bond in order to gain a full outer shell of electrons. This makes them stable They can do this by giving electrons away, gaining electrons or sharing electrons.

Ionic bonding This type of bonding generally happens between METALS and NON-METALS It involves the outer electrons of the atoms. Electrons are transferred between the two atoms Ions are formed which are attracted to each other.

we call this ionic bonding Ionic bonding forms IONS which have positive and negative charges and attract each other

Covalent bonding This type of bonding generally occurs between non-metals It involves sharing electrons to gain a full shell and therefore become stable.

Two H atoms share an electron with O we call this covalent bonding Covalent bonding forms MOLECULES

What do I need to know? Must Recall that chemical reactions can be represented by word equations or symbol equations. Should Describe how no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants. Could Calculate the mass of a reactant or product from information about the masses of the other reactants and products in the reaction.

Word equations A word equation describes a reaction, for example burning lithium in air. lithium + oxygen  lithium oxide Can you write word equations for the following…

Word equations The reaction between potassium and oxygen The reaction between lithium and water The reaction between calcium and oxygen The reaction between rubidium and water

Symbol equations Symbol equations use chemical symbols and are “balanced” to show the actual number of atoms used. For example Li + H2O  LiOH + ½ H2 is lithium + water  lithium hydroxide + hydrogen Note that we don’t generally include the numbers in the word equation.

Change these symbol equations into word equations K + H2O  KOH + ½ H2 2Mg + O2  2MgO Na + H2O  NaOH + ½ H2 Ca + 2H2O  Ca(OH)2 + H2 4Fe + 3O2  2Fe2O3

Change these symbol equations into word equations K + H2O  KOH + ½ H2 Potassium + water  potassium hydroxide + hydrogen 2Mg + O2  2MgO Magnesium + oxygen  magnesium hydroxide Na + H2O  NaOH + ½ H2 Sodium + water  sodium hydroxide + hydrogen Ca + 2H2O  Ca(OH)2 + H2 Calcium + water  calcium hydroxide + hydrogen 4Fe + 3O2  2Fe2O3 Iron + oxygen  iron oxide

Balancing equations Symbol equations need to be balanced because the number of atoms reacting at the start MUST be the same as the number of atoms in the products. An unbalanced reaction cannot properly represent a reaction because there is an imbalance in the number of atoms in the reactants and products. The mass of reactants MUST also be the same as the mass of products.

Calculating masses We can predict the mass of product from the mass of reactants because we know that mass is conserved. Example 2Mg + O2  2MgO If 24 g Mg reacts completely with 16g of O2 what mass of MgO is made? 24 + 16 = 40 g

Calculating masses 2Li + 2H2O  2LiOH + H2 A piece of lithium weighing 7g is allowed to react with 18g of water. We collect 1g of hydrogen gas in the test tube. How much lithium hydroxide has been made? 7 + 18 – 1 = 24 g

Calculating masses C6H12 + 9O2  6CO2 + 6H2O If 84g of hexane (C6H12) are burnt completely in 288g of oxygen we measure 108g of water produced. How much carbon dioxide was given off? 84 + 288 – 108 = 264 g

How to balance When we balance equations we do not change the small (susbscript numbers) eg Ca(OH)2 because this would change the compound itself We do change the LARGE number in front of the compound Eg 2Ca(OH)2 because this changes the amount.