WordsDefinitions

Anion: A negatively charged Ion, one that would attract towards an anode.

Atomic Radius This is the size of the atom and is the distance from the centre of the nucleus to the outer most electrons in a stable atom.

Avogadros number

Cation A positively charged ion that has lost electrons.

Divalent An atom that has two valence electrons (Di-Valent means two-valence).

Ductile To deform without fracture. If something is very ductile, it can be hammered into sheets without damage very easily.

Electron Affinity The amount of energy released when an electron is added to an atom to form a negatively charged ion. It is also the amount of energy required to strip an electron from a negative ion. A higher electron affinity means meaning it is harder to remove an electron.

Electronegativity The ability for an atom to attract electrons in order to covalently bond. The higher electronegativity, the more strongly it will attract them.

Ion An element that has gained or lost an electron and does no longer has the same number of electrons as protons.

Ionisation Energy The minimum amount of energy required to remove an electron from an atom in a gaseous state in order to form a positively charged ion.

Isotope

Malleable Able to be hammered and pressed into shape without breaking.

Oxidation

Valence shell/electrons The outer most shell with electrons/outer most electrons in an atom.

Guide Words in this colour have their definitions in the table of definitions above.Atoms The number of protons in an atom determines what element it is no matter what. The number of protons is also the atomic number of the element. The mass number is the number of protons +neutrons. The number of electrons is the same as the number of protons in atoms in

The Periodic Table The periodic table is a table of elements arranged which shows all the elements arranged from the smallest to the largest. The columns in the periodic table are called Groups with the main groups from 1 to 8. The rows in the periodic table are called Periods and go from 1-7.

As seen in the picture above, it is important to know the properties of the types of elements and where they are found in the periodic table.Alkali Metals: Very Reactive. Malleable, Ductile and good conductors. One loosely bound Valence electron. Reacts violently with water. Forms cations with a 1+ charge.

Alkaline Earth Metals: Low Electron Affinities and Electronegativity Two valence electrons Smaller Atomic Radii than Alkali Metals Readily forms divalent cations with a 2+ charge.

Transition Metals: Fairly unreactive. High melting, boiling point and electrical conductivity. Have a wide range of oxidation states. Have low Ionization energy.

The Halogens: Very high electronegativitys. Seven valence electrons. Highly reactive with alkali metals and alkaline earth metals. Have low Ionization energy.

Metalloids: Have similar metal and non-metal properties. They are all solids. Found in the small step portion of the periodic table.

Noble Gases: Completely unreactive. Full valence shell. Very low electronegativitys. Low boiling points. Gases at room temperature.

The Electrons Electrons are negatively charged particles which orbit around the nucleus of an atom. They determine how the atom behaves and most of its properties.

The Bohr Model: Proposed by the scientist Niels Bohr. The Bohr Model states that electrons have set distances in which they orbit a nucleus. Each set distance is a shell and can be referred to as n. Each set distance has a fixed amount of energy with each electrons in that orbit having that amount of energy. The further distance away you get from the nucleus, the more energy is contained in the orbits.

Orbitals (sub-shells): Within each shell of an electron are orbitals. An orbital is a probability cloud and is defined as an area in space where there is a high probability of finding electrons. Each orbital can only hold a maximum of two electrons. There are s, p, d and f orbitals and each orbital has its own unique shape. Electrons fill shells from the lowest energy level to the highest. The periods in the periodic table represent which shell the electrons will go into.

s-orbital: Found in the first shell of the atom. It can hold a maximum of two electrons. Is a spherical shape. This is why the first period in our period table only has two elements.

p-orbital: Found in the second shell of the atom. The second shell is larger and can include more than just the s-orbital. It can hold a maximum of six electrons. It consists of three configurations along the 3D x-y-z axis with each one holding two electrons.

d-orbital: Found in the third shell of the atom. It can hold a maximum of ten electrons. It consists of five configurations each one holding two electrons.

f-orbital: Found in the fourth shell of the atom. It can hold a maximum of fourteen electrons. It consists of seven configurations each one holding two electrons.

Electron Configuration: Electron configurations are a way of writing down where each electron is located within an atom. It involves three main parts written down to form an equation. In order to write the electron configuration of an atom, we write:1. The number of the shell.2. The letter of the orbital.3. The number of electrons in that orbital.

Electrons fill orbitals in a certain order, from the lowest energy to the highest. A trick we can use to write this is to memorise the following diagram and draw diagonal lines to determine the order in which orbitals will be filled in.

From this diagram, we know that electrons will fill in the following order: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 and so on.

Just by looking at the above equation, we know: This atom has a total of 30 electrons. (Total number of electrons in each orbital. We can determine that this is an atom of Zinc. (Assuming it isnt an ion)

Write the electron configuration for Chromium.

1. Chromium is in the second period of the periodic table.2. It is the 24th element, meaning it has a total of 24 electrons in its natural state.3. We know how many electrons each orbital can hold.4. All we need to do now is look at the diagram and start filling in all 24 electrons for Chromium in the order of the diagram.5. Therefore Chromium has the following electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d4

Ionization Energy: Ionization energy is the amount of energy required to remove an electron from an atom to create a positively charged Ion. When an electron is removed from an atom, it forms a positively charged ion called a cation. This is because before the electron was removed there were an equal number of protons and electrons and hence the overall charge was neutral. Now that the electron is removed, there are more protons than electrons and hence the overall charge is positive. The outer most electrons have the most energy and hence require the least energy to be removed so they are the first to be removed. The closer an electron is to its nucleus, the more energy required to remove the electron. When all of the electrons in the outer most shell are removed, there is a jump in energy required to start removing electrons in the next outer most shell. This makes sense as electrons are being attracted towards the protons in the nucleus and the closer they are, the stronger the force of attraction and hence the more energy required to remove the electron. Energy is also required when adding electrons to form negatively charged ions called anions. This energy is called the electron affinity. The orbitals are also on periodic table as shown below with the number of elements for each row of the orbitals corresponding to the number of electrons the orbital can hold, for example all the s-orbitals in green have only two elements in each row.

Stoichiometry Stoichiometry is the science of measuring chemicals that go into and out of reactions. It allows us to count atoms and molecules by weighing them.

Atomic Mass: The atomic mass of an element is the average number of all the isotopes of that element and their abundance on earth. Atomic mass is measured in atomic mass units (amu). We can calculate atomic mass by adding the number of protons and neutrons in an element. We can also calculate it if given the isotopes and their abundances by using the following steps. Convert the abundance of each isotope of the element from a percentage to decimal. Multiply the abundance of each isotope by its mass. Add the final results of each isotope together.

Relative Atomic Mass: The ratio of the average mass of an atom to 1/12th of the mass of an atom of carbon-12. 1 amu = 1/12th the mass of a carbon-12 (12C) atom which is 1.99264648 x 10-23.

Gallium has two stable isotopes: Galium-69 (60.11% abundant) and Galium-71 (39.89% abundant). Their atomic masses are 68.926 and 70.925 respectively. Calculate the average atomic mass of Gallium.

1. Convert the percentages to decimals.2. 60.11*(1/100) = 0.6011 and 39.89*(1/100) = 0.39893. Multiply the isotopes masses by their abundance.4. Add the results together.5. (0.6011*68.926) + (0.3989*70.925) 6. = 69.72 amu

If you have a look at the periodic table for the mass of Gallium, you will notice it is 69.72 amu.

Moles: A mole is one of the most important units in chemistry. It allows us to express a chemicals atomic mass in terms of grams. A mole is equivalent of the amount of atoms in 12 grams of Carbon-12 which is 6.022 x 1023. This number is known as Avogadros number. A mole of anything means 6.022 x 1023 of that object, so a mole of rice would mean 6.022 x 1023 grains of rice. For example, a mole of oxygen would mean 6.022 x 1023 atoms of oxygen which in total comes to 16 grams. If you look at the period table, the relative atomic mass of oxygen is 16 amu. This is known as the elements Molar Mass. To calculate the molar mass of a compound, you must add the molar mass of all the individual elements. Calculate the Molar Mass of Sucrose C12H22O11.

1. Find the Molar mass of each atom in sucrose from the periodic table. 2. Carbon = 12.01, Hydrogen = 1.008, Oxygen = 16.00.3. Multiply the number of atoms of that element in sucrose by its molar mass from the periodic table.4. C = 12.01*12 = 144.12 g, H = 1.008*22 = 22.176 g, O = 16*11 = 171 g.5. Add the total Molar mass of all three elements that make up sucrose.6. 144.12 g + 22.176 g + 171 g = 342.926 g7. This means that the total mass of C12H22O11 weighs 342.926 g.

Reactions: A reaction takes place when atoms of the same or different elements react together to form a new substance. A reaction involves the reactants which are the elements that are being rearranged and the products which are the new substances that are formed due to the reaction. The total number of atoms of each element remains the same before and after the reaction. (Conservation of mass)

Balancing Equations: A balanced equation is an equation that has an equal number of each element on both sides of the equation. This involves the law of conservation of mass. This equation is used to tell you how much of each element goes into and comes out of the reaction. In order to balance an equation we use the following steps: Start with the most complicated molecule. Now since the goal is to have an equal number of each atom on each side of the equation, we start multiplying atoms by certain amounts on each side of the equation until we end up with a balanced equation. We demonstrate this by placing a number beside the element to show how many of that element is required.

Balance the following equation of sucrose:

C12H22O11 + O2 = CO2 + H2O

1. We first start with the most complicated molecule, in this case C12H22O112. Now there are 12 carbon atoms on the left side of the equation and only 1 on the right hand side. We can immediately put a 12 beside the CO2 so now with 12 carbons on both side of the equation, the carbons are balanced out.3. Now we can move onto the Hydrogen atoms. There are 22 on the left hand side and only 2 on the right hand side. We can put an 11 beside the H2O so now the Hydrogens on both sides are balanced out.4. Finally, there are 13 Oxygen atoms on the left hand side and 35 on the right hand side. We can put a 12 beside the O2 to balance the Oxygen atoms out.5. The final equation we end up with is C12H22O11 + 12 O2 = 12 CO2 + 11 H2O which has both sides of the equation balanced with equal amounts of elements.

Molar Ratios: Molar ratios are used to calculate the amount of a compound for a certain amount of another. By some simple mathematics, you can calculate your answer.

How much Oxygen would you need to inhale in order to burn 5 grams of:

C12H22O11 + O2 = CO2 + H2O

1. To solve this, first we balance the equation. From the last question: C12H22O11 + 12 O2 = 12 CO2 + 11 H2O g.2. Next, we convert the equation to moles in order to make it into grams. Doing this we get 342.296 g C12H22O11 + 348 g O2.3. Now thats 342.296 g of sugar for every 348 g of Oxygen. Now to find out how much Oxygen for each gram of sugar, we divide 342.296/348 which equals out to be 0.984 g of sugar for each gram of Oxygen.4. Now for 5 g of Oxygen, we need 0.984*5 g of sugar which is 4.92 g.

Water and Solutions A solution is a substance that is capable of dissolving another substance. Water is the best solutions on earth as it is capable of absorbing more than anything else.

Solutions: A Solution is the process by which a gas, liquid, or solid is dispersed homogeneously in a gas, liquid, or solid without chemical change. A Solution is made of a Solvent which is a substance or substances and a Solute which is the main substance it will be dissolved in, usually liquid. A water base solution is called an aqueous solution.

Water: Water is the best solvent on earth for various reasons. It is very abundant all over the earth. It is liquid at a wide range of temperatures. Its very polar.

Electronegativity: Electronegativity refers to the ability for an atom to attract shared electrons. Every atom on the periodic table has a number with the highest being the most electronegative. This number increases from left to right on the periodic table as the number of protons increases which means more positive charges. This electronegativity decreases as you go down the periodic table as the electrons begin shielding themselves as they increase in number. These values can be seen in the table below along with the trend due to the shielding effect and increase of protons.

Polarity: Polarity refers to having one side slightly positive in charge and the other side slightly negative. For a molecule to be polar, it cannot be made of the same elements as the electronegativity of both elements is the same and one side will not be more negatively charged than the other. For a molecule to be polar, the difference between their electronegativys must be greater than 0.5. When the difference is greater than 0.5, the valence electrons of the atoms spend most of their time around the more electronegative atom.

This result in one side of the molecule being slightly negative and the other side being slightly positive. This is called a Dipole Moment and is required for a molecule to be polar. A dipole moment is when there is one part of a molecule which is negatively charged and the other part positively charged. When one of the atoms in the molecule is more electronegative, it will pull not only its own but also its neighbouring electrons closer towards itself. This will lead the electron cloud of negativity to be greater on one side than the other and hence a polar molecule. This is seen in the picture to the right. Although if the atom is symmetrical, the distribution of charges may cancel each other out making the molecule non-polar. This can be seen in the following pictures with these opposite charges cancelling each other out:

In order to show the dipole moment of a molecule is electronegative, we draw an arrow sign with a plus sign at the tip and facing the electronegative side as shown in the picture below. We also put the delta + and delta also shown in the picture.

Effects of Polarity on Solutions: When there is a polar solution, all the molecules want to be arranged in a way where they are in their lowest energy state. This is achieved by each individual atom in a molecule attracting the oppositely charged atom of the neighbouring molecule until all the atoms are perfectly arranged. This can be seen below in picture of these molecules of water. This can also physically be seen in a glass of water and is why a glass of 100 mL can hold a little over 100 mL of water also as seen in the picture below.

This leads to all the molecules of water or other polar solutions being arranged in a way that achieves the lowest surface area. When a non-polar liquid is added to a polar solution such as oil being added to water, this mixture of non-charged oil molecules and charged water molecules will not want to mix. Water will continue to do everything it can to minimise its surface area much like when there is air in a solution it tends to rice, the same will occur with the molecules of the non-polar solution as they will be pushed up as the molecules of water attempt to reorganise themselves back into their lowest energy state and surface area.

Dissolving: When something is dissolved, it is absorbed by another substance without any chemical change occurring. A polar substance will dissolve other polar substances such as water dissolving salt or sugar. There are two different ways molecules can be dissolved which depend on the type of atoms in the molecule: Polar substances such as water are able to weaken the attraction between ions of different charges. This is due to its Dielectric Properties and it is what allows water and other polar substances to break down ionic bonds and attach to their opposite charges.

Ionic compounds dissolving in polar solutions: Ionic compounds are made up of molecules which are bonded together through the attraction of oppositely charged ions in what is called an Ionic bond. Ionic compounds involve molecules that are made up of metals + non-metals. Salt is an example of an Ionic compound as it is made up of Na+Cl- made up of two oppositely charged ions bonded together. When a molecule made up of an ionic bond is dissolved by the molecules of the of the solute, the individual atoms of the ionic bond break up from the bond and each ion is attracted to the opposite charge of the molecules of the solute. In the example of salt dissolving in water, the Na+Cl- would lose its bonds and the Na+ would be attracted to the negative side of the water (H2O) whilst the Cl- would be attracted to the positive side of the water molecule. Once the ions are surrounded by the water molecules, they are now shielded from the other oppositely charged ions.

Covalent compounds dissolving in polar solutions: Covalent compounds are made up of molecules which are bonded by sharing electrons in a covalent bond. A compound that is covalently bonded dissolves in a polar solute; its covalent bonds will not be broken up into their individual atoms. Sugar is an example of a covalent compound as it is made up of C2H4O2 molecules. When a molecule made up of a covalent bond is dissolved by the molecules of the of the solute, the individual molecules of the covalent bond break off and the water molecules attach its charged sides to the oppositely charged sides of the molecule of sugar.In an example of sugar dissolving in water, the C2H4O2 would keep its bonds and H2O molecules will attach themselves to the molecule of sugar.

When a soluble substance is placed in a solute, there are various factors that may affect how well it dissolves and is absorbed into the solution:

The size of the molecule: Given the same size of a substance, smaller molecules will have a larger surface area than bigger ones. A particle that is larger in size will be absorbed by the solvent quicker. This is due to the particle having a larger surface area, which means more molecules of the solute are exposed to the molecules of the solvent which.

Temperature: The higher the temperature is, the more the solvent will dissolve. This makes sense because a higher temperature means more kinetic energy, so the particles are moving a lot faster, which means there will be more collisions with the solute breaking it down at a quicker rate. Increasing the temperature also increases the maximum amount of the solvent that can be dissolved in the solution, not only the speed at which it is absorbed.

Agitation: Agitation includes physics actions such as stirring or shaking the solvent and the solution together. This also works by increasing the Kinetic energy of the particles and causing more collisions.

Chemical nature of solute: A polar substance WILL dissolve in another polar substance. Two substances that can dissolve each other are called Miscible. A polar substance WILL NOT dissolve a non-polar substance. Two substances that cannot mix or dissolve each other are called Immiscible. This leads to a commonly used phrase like absorbs like.

Electrolytes: An Electrolyte is the name given to an ion that has been dissolved into a solution. This is due to the ion now being able to float freely in the solution while carrying its electrical charge around. Water for example is a poor conductor of electricity, but when you dissolve salt into water, it becomes a better conductor of electricity due to the now dissolved ions of the salt becoming electrolytes and able to carry and conduct electricity. Due to this concept, we know that a solutions electrical conductivity can be related to the amount of ions dissolved in the solution. The higher amount of electrolytes in a solution, the higher its electro conductivity. This can also be reversed to measure how concentrated a solution is by measuring its electrical conductivity. Not all electrolytes can conduct electricity equally well; due to this we have strong electrolytes and weak electrolytes. If a substance doesnt dissolve to form ions in the solution, the electrical conductivity will remain the same.

Strong Electrolytes: Strong electrolytes conduct electricity very well. They are made up of Ions that dissolve very well solutions. Salts are able to form strong electrolytes as Na+Cl- dissolving completely to form Na+ and Cl-. Strong bases or strong acids like H+Cl- are also another example of strong electrolytes as they break down completely to form H+ and Cl-.

Strong Electrolytes: Weak electrolytes do not conduct electricity very well. They are made up of Ions that dissolve partially in solutions. NH4+OH dissolve partially into NH4+ and OH which results in weak electrolytes as only the NH4+ is an ion and the NH4+ is just a molecule.Acid-Base Reactions in Solutions An acid is a molecule or ion that, when placed in water, will give up a hydrogen ion (H+) to a base, or accept an unshared pair of electrons from a base. Water is the best solutions on earth as it is capable of absorbing more than anything else.

Acids and Bases: H+ ions are also referred to as protons. An Acid is a molecule or ion that, when placed in water, will give up a hydrogen ion H+ to a base, or accept an unshared pair of electrons from a base. An acid is a solution that has more free H+ atoms than OH-. A Base is a substance which dissociates (separates) in aqueous solution to yield hydroxyl ions OH- or negatively charged hydroxide ions which react with an acid to form a salt. A base is a solution that has more free OH- atoms than H+. Acids and Bases react with each other in a Neutralization Reaction to form a salt. An easy way to think of it is an acid has the H+ ion and a base has the OH- ion. When an acid is place in water, it will give up its H+ ion.

Neutralisation Reactions: When an acid is added to water, it donates a H+ to the water. This leaves us with a positively charged hydroxide ion H3O+ (which is a H2O molecule that has gained a H+ ion) and a salt. This can be seen in the picture to the right which shows three different acids donating a H+ ion to water to form a H3O+ ion and a negative ion or a salt. In these reactions, water can react as either a base or an acid. If it gains a H+ ion then it is a base or if it loses a H+ ion then it is an acid. The products of the reaction are called the conjugate acid and the conjugate base. If it is a conjugate acid, then it has lost a H+ ion but, if it is a conjugate base then it has gained a H+ ion. This can be seen in the picture on the right of hydrochloric acid HCL acid reacting with water. For every acid there is a conjugate base and for every base there is a conjugate acid. A strong acid is an acid that really likes to get rid of its H+ ion and one once it does it is very hesitant in taking it back so its conjugate base is a weak base and vice versa.

Precipitation Reactions: This is when a solid is formed when reacting two aqueous solutions.

Bonds Atoms can form different type of bonds including the main three: Ionic, covalent and hydrogen bonds. An atom is most

Atomic Mass: The atomic mass of an element is the average number of all the isotopes of that element and their abundance on earth.Atomic mass is measured in atomic

Ionic Bonds: Ionic bonds form when a metal and a non-metal share electrons and bond together forming a molecule (For Example: NaCl). This type of bond occurs in three main simplified steps:

1. An atom donates electrons and another atom receives the electron.2. This causes an imbalance in charges in each atom with the atom gaining the electron now being negatively charged and the atom donating the electron having a positive charge.3. The two atoms attract to each other due to the opposite charges and an ionic bond is formed.

Ionic bonds are formed due to atoms wanting to have a full valence shell. In the Na+Cl example, by forming an ionic bond, both elements now have a full valence shell. All atoms in their normal form have a neutral charge due to the balance of protons and electrons. By gaining and losing electrons, this creates an Imbalance in the charges resulting in a positively or negatively charged atom. Due to the change of electrons in the Na and the Cl, they are no longer atoms but are now called Ions. The positively charged Ion (Na+) is called a Cation and the negatively charged Ion (Cl-) is called an Anion. Once the ionic bond between both ions is formed, the overall charge of the molecule formed is neutral as the charges of both ions cancel each other out (This means the molecule formed is NaCl not Na+Cl-). We have now created Sodium Chloride. Now say we have many Na and Cl atoms all forming ionic bonds with each other, due to the positive and negative charges of the ions formed, they will all combine together to form what is called a Lattice Structure. This forms when the negative side of multiple Na+Cl- bonds combines with the positive side of other Na+Cl- bonds and vice versa eventually forming the Lattice structure shown below.

Electronegativity

Electronegativity is a measure of how desperately an atom wants to gain electrons. The more electronegative an atom is, the more it wants to gain electrons. Na with an electronegativity of 0.9 is not very electronegative compared to Cl with an electronegativity of 3.0. This is why Na loses an electron while Cl gains one. Generally, metals are not very electronegative compared to non-metals which are usually very electronegative.

Ionic Charges

Atoms can form ions of different charges depending on which column or group they reside in the periodic table. It is more beneficial to know what charge each Ion gets by understanding the concept behind the charges. Keep in mind that each atoms goal is a full valence (outer) shell and all the atoms originally have an equal number of protons and electrons which maintains their neutral charge.

In Group 1, all the atoms have 1 valence electron which they would prefer to donate in order to achieve a full valence shell. Once donated, these atoms now have 1 less electron than protons. This leaves them with an overall positive charge of +1. In Group 2, all the atoms have 2 valence electrons which they would also prefer to donate. Once donated, they now have two less electrons than they do in protons and now have an overall charge of +2. In Group 3, the concept is still the same as they have 3 valence electrons and lose them to achieve a charge of +3. Now Group 5 has elements which prefer to gain electrons rather than donate them. They have 5 valence electrons and would prefer to gain another 3 to achieve a full valence shell. Once they gain those electrons, their overall ionic charge becomes -3 as they have 3 more electrons then protons. In Group 6 and 7, they gain 2 and 1 electrons respectively and will have a charge of -2 and -1 respectively. Finally, Group 8 will not gain or lose any electrons as they already have a full valence shell and thus do not form ions.

Balancing Charges

In the example of NaCl, the Na is in group 1 and has an ionic charge of +1 while the Cl is in group 7 and has an ionic charge of -1. These two charges are the same and do not need balancing but this is not always the case. An example of this is Lithium Oxide (Li2O) where Lithium sits in group one having a +1 charge and Oxygen sits in group 6 having a -2 charge. These two charges do not balance out and thus we need to balance them ourselves. We can do this by adding more of either atom until the total charges are balanced. In this example, we can add two Lithiums for every Oxygen. This means that the charge for the two Lithiums is now +2 which the same as the charge for one Oxygen. Now we have balanced out Lithium Oxide. This means for every Oxygen atom, were going to have two Lithium atoms. This can now be written as Li2O.

What is the Ionic bond for Aluminium Oxide?:

1. Aluminium is in the 3rd group, which means it forms an Ionic charge of +3.2. Oxygen is in the 6th group, which means it forms an Ionic charge of -2.3. In order to balance this one out, we need to find the lowest common multiple of 3 and 2. 4. We cannot have half an Oxygen atom, but we can add more of both elements.5. By having 2 Aluminiums, the total charge is for Al is now +6. 6. Now we can add 3 Oxygens to make the total charge for Oxygen -6.7. Finally, the balanced Equation for Aluminium Oxide is Al2O3.

Covalent Bonds:Ionic16