Slides in this set
A salt is a compound formed from an acid when a H + ion from the acid has been replaced by a metal ion or another
Avogadro constant is the number of atoms
positive ion. The positive ion (cation) is usually a metal ion or an ammonium ion NH 4 +. The negative ion (anion) is
in one mole of any element. 6.0225 x 1023
derived from the acid. The formula is the same as the initial acid, but the H + ion is replaced with the cation. Salts
The mass of one mole of any atom is their
are formed by adding either carbonates, bases, or alkalis to acid to neutralise it.
relative atomic mass.
Mass number = Proton + Neutron There are two H + ions in sulphuric acid. This is called a diprotic acid. When one H + ion is replaced, an acid salt is
Atomic number = No. of protons and No. of electrons formed, e.g. sodium hydrogensulfate. H2SO4 NaHSO4
Neutrons = Mass number Atomic number The process can be repeated with the acid salt to make a normal salt because the other H + ion can be replaced.
To work out the relative atomic mass, multiply the Ammonium salts
mass number of each isotope by its relative These are formed when acids are neutralised by aqueous ammonia. In this reaction, the ammonium is the cation.
The molecular formula is the actual
abundance divide by 100 and then add the Ammonium nitrate is present in solution as two ions, NH4 +(aq) & NO3-
number of atoms of each element in a
numbers together to get the relative atomic mass. NH3(aq) + HNO3(aq) NH4NO3(aq)
molecule. It tells you the number of
Relative molecular/formula mass can be found by Calculate the percentage of nitrogen in fertiliser:
each type of atom that make up a
adding the relative atomic mass of each atom Find the molar mass of ammonium salt. Then, find the mass of nitrogen in 1 mole and calculate the percentage of
within the compound. nitrogen in the ammonium salt. : 28 / 80 x 100 = 35%
To work out the molecular formula, find
Empirical formula is the simplest whole-number ratio of Hydrated refers to a crystalline compound containing water molecules. Anhydrous is the form that has no
the empirical formula and calculate the
atoms of each element present in a compound water molecule. Water of crystallisation refers to water molecule that form an essential part of crystalline
relative atomic mass. Then divide the
To work out the empirical formula, you first find the molar structure of a compound. Without water molecules, the compound cannot usually be crystallised.
relative molecular mass by the relative
ratio of atom. Then divide both by the smallest number and atomic mass. Multiply each atom in a The empirical form of the compound is separated from water crystallisation by dots. After the dot, the
you will get the ratio to 1:X. relative number of water molecules is shown.
formula by the answer; so if the answer
Here is an example: To work out the formula of a hydrated salt, you use the method to work out the empirical formula, but you
is 4 and the empirical formula is CH , the
0.6075g of magnesium combines with 3.995g of bromine to molecular formula is C4H also do a step for the dot formula. Using the number of hydrogen atoms, you can work out the number of
8 Species Oxidation Number Examples
form a compound Oxidation numbers are derived from a set of water molecules of crystallisation. The oxygen needs to be considered of the split between the water
(Mg, 24.3; Br,79.9) rules. There are some exceptions. molecules and the ions, such as sulfate, nitrate and carbonate ions.
Uncombined Elements 0 C, Na, O2, P4
Find the molar ratio of atoms : Exceptions: The formula of hydrated salt can be determined by heating it so the water crystallisation is evaporated. The
Mg : Br · When bonded to fluorine, oxygen has an results needs to include the mass of the hydrated salt, mass of the anhydrous salt and the mass of the water
Combined oxygen -2 H2O, CaO
0.6075 : 3.995 oxidation number of +2. In peroxides, oxygen that the hydrated salt had. The elements that form compounds and ions
24.3 : 79.9 has an oxidation number of -1. Combined hydrogen +1 NH3, H2S Oxidation is loss of electrons and an increase in have oxidation numbers, so oxidation number of
0.025 : 0.050 · When hydrogen is bonded with metals in oxidation number. Reduction is gain of electrons and a the element is included in the name of
Divide by the smallest number (0.025): 1 : 2 hybrids, it has an oxidation number of -1. Simple ion Charge on ion + 2+
Na :+1, Mg :+2, Cl :-1- decrease in oxidation number. compound and ion as roman numeral.
The empirical formula is MgBr
The overall charge n he compound is always Redox reaction is when both reduction and oxidation Oxyanions
equal to the oxidation number. Combined fluorine -1 NaF, CaF2, AlF3 reaction take place. These are negative ions that contain an element
Ionic bonding occur between a metal and a non-metal that want to bond. The structures in this are giant Reaction between a metal and a non-metal is usually a along with oxygen (SO42-, NO3-,CO32-)
structures; so they have a very high melting and boiling point. redox reaction. The metal is a reducing agent because it An element may form oxyanions in which the
Electrons are transferred from the metal atom to the non-metal atom. Oppositely charged ions are reduces the non-metal by donating its electron. The non- element has different oxidation number
metal is a oxidising agent because it oxidises the metal - NO2- Nitrate(III) N: o.n: +3
formed so they attract by the electrostatic attraction. The metal becomes the positive ion and the non-
metal becomes the negative ion.
F321 by removing its electron. - NO3- Nitrate(V) N: o.n ; +5
For example, Sodium oxide, Na2O; - SO32- Sulphate(IV) S: o.n; +4
A sodium atom has 1 electron in its outer shell and an oxygen atom has 6. For the oxygen to become Metallic bonding occur between metal atoms. In these bonding, the atoms are ionised. Positive ions occupy fixed positions in a
stabilised with full outer shell, it needs two more electrons. When the sodium transfers its electron to the lattice. The outer shell electrons are delocalised so they are able to be shared between other atoms in the structure. This allows
oxygen, the sodium becomes a positively charged ion and the oxygen becomes a negatively charged ion. the electrons to be move freely within the structure, which gives them the characteristic to conduct electricity. A giant metallic
However, the negatively charged oxygen ion still needs one more electron in its outer shell for a full outer lattice is referred to as positive ions surrounded by a sea of electrons. Over the whole structure, the charges must be balance.
shell. So another sodium atom arrives and transfers its electron to the oxygen. Now, there a two positively Also, the giant lattice structure makes the melting and boiling points to be very high. This is because the attraction between the
charged sodium ions, and one double negative oxygen ion with a full outer shell. positive ions and delocalised ions are really strong so a lot of energy is needed to break down the structure.
Giant ionic lattice The delocalised electrons a responsible for the metals ability to be ductile and malleable, because the ability to move allows the
This is a 3D structure of oppositely charged ions, held together by strong ionic bonds. For example, in the layers to slide on top of each other.
giant lattice structure of sodium chloride, each +ve charged Na ion surrounds 6 ve charged Cl ions. Each Electron-pair repulsion theory Elements and compounds with covalent bonds can be a simple molecular lattice or
ve Cl ion surrounds 6 +ve Na ions. There's millions of ions in the structure; depending on the size of the The shape of a molecule or ion is determined by the number of electron giant covalent lattice.
crystal. All ionic compounds exist as a giant ionic lattice in the solid state. configuration, particularly the outer shell. Being negatively charged, each electron Simple molecular lattice
Covalent bonding occur between non-metals. Non-metals generally want to gain electrons to become stabilised, and pair repels other electron pairs. They are made up from small simple molecules such as Ne, H2, O2, N2 etc.
not lose any. When two non-metals bond with each other, they share electrons amongst themselves. One electron is In a solid simple, molecules are held together by weak forces between molecules.
shared by each of the atoms. These bonding can be simple and giant structures. The simple structures have a very low A lone pair is an outer shell electron pair that isn't involved in chemical bonding. It The atoms bonded together within the molecule are strongly bonded by covalent
melting point, and low boiling point, whereas giant structures have an very high boiling and melting point. gives a very strong, dense negative charge region on the atom. The number of lone bond.
Single covalent bonds pairs in the outer shell determines the angle of the bond between the atoms. These types of structure have a weak melting and boiling point because the
These are when compounds need to bond by sharing only one electron between themselves. For example; hydrogen, · No lone pair would make a tetrahedral shape with a bond angle of 109.5 intermolecular are weak so not much energy is needed to break the bonds.
H2. degrees. They don't conduct electricity because they don't have free charged particles that
A hydrogen atom has one electron in its outer shell, and it need one more to become stabilised. Therefore, another · One lone pair would make a pyramidal shape molecule with a bond angle move.
hydrogen atom will bond together to provide each other another needed electron. When they share the electron, of 107 degrees. Giant covalent structures
both hydrogen atoms now consist two electrons in the outer shell, which means it is stabilised. They are written as H · Two lone pair would make a non-linear shape molecule with a bond angle A 3D structure of atoms, bonded together by strong covalent bonds. Diamonds and
H. of 104.5 degrees graphite are two allotropes of the element carbon, i.e. they're different crystalline
· The number of covalent bonds formed by the atoms of: - C : 4 - N : 3 - O : 2 - H : 1 The relative strength of repulsion are: structures. They are examples of giant covalent structure. They have extremely high
Multiple covalent bonds Lone pair lone pair > bonded pair lone pair > bonded pair bonded pair melting and boiling points and the don't conduct electricity except from graphite.
Some covalent bonds can share more than one pair of electrons . Diamonds is in a tetrahedral shape held together by strong covalent bonds
Sharing two pairs of electrons forms a double bond. (written as 0 = 0) . Sharing three forms a triple bond. Carbon Molecules with double bonds throughout lattice. There's no free charged particles so it cannot conduct electricity.
dioxide has two double bonds; O = C = O. A double bond has four electrons as two bonded pairs. To work out the shapes of a All the carbon atoms have all four bonds filled which give the structure the hardness.
molecule with a double bond, each double bond is treated as a bonded region, in However, graphite is an a strong hexagonal layer structure, but has weak van der
Dative covalent bonds the same way as a bonded pair. Waals' forces between the layers. Also, there are delocalised electrons between the
Coordinate bond is a shared pair of electrons which has been provided by one of the bonding atoms only. This For example, carbon dioxide has two double bonds which will repel each other to layers which gives the ability to conduct electricity. This also makes the graphite to
normally happens with the lone pair of electrons. It is written as A B . The direction of the arrow shows the direction be as far apart. This will make the shape of the molecule to be linear with a bond be soft as the weak forces between the layer allows the layers to slide easily.
in which the electron pair has been donated.…read more
The first ionisation energy is a measure of how easily an atom loses its first
electron from its outer shell. There a few factors that influences the
· The greater the atomic radius, the smaller the nuclear attraction
experience by the outer electrons
· The greater the nuclear charge, the greater the attractive force on the
· Electron Shielding/Screening is when the inner-shells electrons repel the
outer-shell electrons. This more inner shells there are, the larger the
shielding effect and the smaller the nuclear attraction experienced by the
Successive ionisation energies are a measure of the energy required to
remove each electron in turn.
· Each successive ionisation energy is larger than the one before.
· As each electron is removed, there is less repulsion between the electrons
and each shell will be drawn in to be slightly loser to the nucleus.
· As the distance of each electron from the nucleus decreases slightly, the
nuclear attraction increases. More ionisation energy is needed to remove
each successive electron.…read more