Ionic Compounds

Ionic compounds are different from ionic-bonded atoms.

As normal ionicly bonded atoms, they will lose their electrons and another element will gain them, causing the two atoms to be electrostatically attracted to each other. However, ionic compounds, have more than two atoms bonded together.

When this happens, the atoms will form in a sort of checkerboard pattern. If many atoms bond like this, the compound will be cube-shaped, which we named 'regular lattice structures." These structures will often be drawn or depicted as the cube shape. Still, with small spheres on its surfaces, another way we can depict this is we use a diagram named the "ball and stick diagram", which are similar but they instead draw or model each atom connected via a stick.

Something interesting about ionic compounds is that they have very high melting and boiling points, and they can conduct electricity, but most of the time we have to dissolve them in water or melt them down for electric conductivity, like putting salt in water to make the water more conductive, but what matters is the amount of charged particles

The boiling and melting points change depending on the strength of the bonds of atoms held together, and if the bonds in ionic compounds are very strong, more energy is required to break apart the bonds.

But if you want the ionic compound to conduct electricity, it first needs to have charged particles, if you take any solid it will be tough because all the bonds are stagnant, but if it melted or dissolved then the ions in the solid are free to move and conduct. 

In ionic compounds, one element would have to lose and one would have to gain an electron, for example, if you wish to write aa Sodium bonding with a Chlorine atom, which the Sodium has a +1 charge while the Chlorine has a -1 charge. 
So to have them bond, the Sodium would lose the electron while the Chlorine would gain one, thus, you would write this equation as NaCl+.  

But what happens if the atoms need more electrons to bond, what about Magnesium and Chloride, Magnesium needs to lose 2 electrons since it is in group 2 of the periodic table.
So the Magnesium loses 2 electrons to be a 2+ ion, then we need to balance it out, so we must take two Chlorine ions since one ion is only a -1, so if we were to write this out it would be MgCl2. 

Complex compounds like Calcium Hydroxide or Aluminium Sulfate are, more complicated as these ions aren't single elements so their atomic numbers or electron amounts are not on the table.

Instead, we will have to memorise it, for the Calcium Hydroxide is OH-, while the Aluminium Sulfate is SO42-.
Now we can look at the elements by themselves, Calcium is group 2 of the periodic table which means that Calcium or Ca has a +2 charge, while hydrogen is a -1 charge. 

Similar to the Chlorine atom, a single Hydroxide has a -1 charge, which means we need to put two of them in the CaOH- equation instead of one, the written formula for this is:
Ca(OH)2.
The reason why we put the 2 outside the brackets is because it means whatever is inside the brackets there is 2 of them. 

Now to tackle the Aluminium Sulfate, the Aluminium has a +3 charge, while the Sulfide ion has a -2 charge, this makes it a little bit more complicated because when two compounds bond they need to have the same amount of electrons.

But the problem is we can't add another electron to the Sulfate, in order for this to work we would need to first find the lowest multiple of both of the charges, which 3*2 is 6, so six is the smallest multiple we can find. 

So in order for this to work out we need 3 * 2 to get us 6, which we will take two Aluminium both of which are +3 charge, and three Sulfate ions, which means we have our 3 * 2.

So we would write this as: Al2(SO4)3. 

That's how we would write it, as we need 2 Al atoms the smaller scale 2 is there, then there is the SO4, which means the chemical writing for Sulfide, then the small 3 at the end means that there are three of the Sulfate ions. 

Other ionically bonded compounds are: NO3- for a Nitrate ion, a carbonate ion which is CO3^2-, and lastly is the Ammonium ion which is NH4+. 

Ionic Bonding

As we know, atoms can bond together via ionic bonds, which happen when two atoms share the Valence electrons, which are the electrons on the outermost shell. 

Ions are created when an atom loses or gains an electron, this helps the atom to become stable, by having a full outer shell.

If we take Chlorine, which has 17 electrons in its shells and needs only one electron to form a Chlorine ion, the Chlorine atom will take that electron from another atom for example a Sodium atom or Na , which we write like this Cl+e- = Cl-.

But these don't happen by themselves, as the elections need a type of

Foundation of ions.

Ions are charged particles, certain particles can form ions better than others, the reason why some elements want to become ions is because they want to have full outer shells to become stable molecules.

Elements need energy to lose or gain an Electron, so the fewer electrons an element has, the easier it is to lose them, for example, group 1 elements or the Alkali metals can lose their electrons very easily to become -2 ions.
Like group 6, which only needs to lose 2, and group 7, which only needs to gain one, groups 3-5 need to lose 3 electrons, making it harder for them.

We can depict these ions in equations, for example, an equation may look like this:
Na + e-.
This depicts a Sodium atom becoming a Sodium ion.

Cl + e- = Cl-.
This depicts a Chlorine atom becoming a Chlorine ion.

Now something to keep in mind is that when an atom is losing electrons and becoming a positive ion, then we put the electron on the right of the equation.
But if we put the electron on the left of the equation, it means the atom is combining with the electron to.

If an atom loses or gains multiple electrons, like an element like Magnesium, so we would write something like: Mg^2+ + 2e-, so this means Magnesium + 2 electrons.

Group 7 & Group 0 (Halogens & Noble Gases)

 Halogens are very dangerous, these are the Halogens:

Florine is a poisonous yellow gas and is very reactive.

Chlorine is less reactive than fluorine but is a poisonous green gas.

Bromine is a dark brown liquid, once again the odour and liquid are poisonous, and the vapour that it creates is heavy, so you can pour out its vapour from a glass ampule

Iodine is a dark purple solid that forms poisonous purple vapours, but it is also a commonly used antiseptic in medical applications. 

Tennessine.

Atatine.

But we will mainly talk about the elements starting from Florine to Iodine, but the elements Tennnessine and Atatine are still important to remember.

All halogens exist as pairs of atoms, referred to as diatomic molecules. This term indicates that these molecules consist of two atoms. They form these pairs by sharing electrons through covalent bonds. Additionally, halogens can bond with other non-metals, such as carbon or hydrogen, using the same covalent bonding mechanism.
Chlorine bonding with Carbon can get you Carbon Tetrachloride.

Unlike the Alkali metals, the Halogens increase their boiling and melting points the further down you go on the chart.
Along with the boiling points increasing, the reactivity decreases, making the elements less reactive.

The reason why they become less reactive is because the electrons get further from the positive nucleus.

When Halogen ionic bonds with metals and collects an electron to become a minus -1 electron, we call those Halides, so we change the 'ne' at the ends of the names of the Halogens so when Bromine bonds with a metal it becomes Bromide, Iodine becomes Iodide, Chlorine becomes Chloride, and Fluorine becomes Fluoride.

Most of the time they bond with the Alkali metals, an example is Sodium Chloride, the Sodium is an alkali metal while the Chloride is a Halogen.

Another thing that Halogens do is that they do something called 'Displacement Reactions', which means that the more reactive Halogen displace the less reactive ones.

So if we pumped some Chlorine gas into a solution of potassium bromide, so the chemical numbers would be Cl(g) + 2KBr (aq), since Chlorine is more reactive than Bromine, it will displace the Bromine causing the element to become 2kCl(aq).

Something to keep in mind is that more reactive Halogens will always displace less reactive ones.

Helium.

Neon.

Argon.

Krypton.

Xenon.

Radon.

They are named the Noble Gases, these are special because they have full outer shells, causing them to be inert and being unreactive, along with that, they are non-flammable and their boiling points increase the further you go down. 

 

Alkali Metals - Group 1

 Alkali metals are a different type of metal, these metals are as follows, from top to bottom.

Lithium.

Sodium.

Potassium.

Rubidium.

Caesium.

Francium.

These elements unlike most other metals, have low melting points, are brittle and have very low densities, Caesium, for example, explodes at room temperature and is reactive to Oxygen, and they get more reactive the further you go down the chart, and for another example, lithium which is used in lithium-ion batteries are explosive when in contact with water. 

Along with being more reactive the boiling points and the melting points decrease meaning the further you go down the easier it is to melt or boil the water, the reason why these elements or atoms are so unstable is that they only have one electron in their outer shell,
and since they only have one electron in their outermost shell, another reason why they are extremely reactive is because the single electron is on the outer-most shell which is very far from the central nucleus of their atom.

They often combine with non-metals to form ionic compounds, these happen by the Alkali atom donates its singular electron to another element.
Which in this case will be a Chlorine atom, when the Sodium atom loses its electron it becomes an ion, and since the Chlorine atom gains an electron it becomes negatively charged while the Sodium atom becomes positively charged thus making them both attracted to each other. 

When an Alkali metal comes in contact with water, it forms Metal-Hydroxide and Hydrogen gas, which in chemical terms would be written as:
2Na + 2H20 = 2NaOH + H2.

But from Potassium onwards, the elements get so reactive that they will ignite the hydrogen gas, and we know hydrogen gas is very explosive. 

Na+ Cl = NaCl, or Sodium + Chlorine = Sodium-Chloride, this ionic compound is a common table salt which is used in foods.

When these Alkali metals come in contact with Oxygen, they become metal oxides, for example, if we take Lithium and mix it with oxygen we get Lithium Oxide or Li20, or if we take Sodium and combine it with Oxygen we get Sodium Oxide or Na20, 
Or Potatsium and Oxygen we get Potasssium Peroxide or K2O2, or KO2, which is Potassium superoxide.

Metal and Non-Metals

Most of the elements on the periodic table are metals, these metal elements form positive ions when reacting, while most non-metals don't form anything.

To our knowledge, all atoms want a full outer shell to be stable. If an element is found on the left, the number of electrons on its outmost shell is less than on the right side of the shell.   

Metals become more reactive the lower you go on the periodic table because the further you go down, the more shells an element has. For example, Lead or Pb has six shells.
And since the positively charged nucleus is what keeps the electrons in their place, and the lead atom's electrons are far away from the nucleus, the lead atom can lose the electrons easily, this feature is what makes the bottom-most atoms more reactive than the ones at the top. 

Metals are metallic bonding, which is special as their bonds are special to their element, and are very strong compared to other types of bonds, things that metals can do are as follows:

Copper has high melting points, is malleable can be bent or hammered into shape, and is a great conductor of heat and electricity. That's why we use copper in wires so often.
Another thing that metals can do is be sonorous which is the ability to make loud sounds when struck, this is why we use them in gongs, and commonly shiny metals are often used in jewellery.

Compared to non-metals which are very dull in colour and are often terrible at conducting electricity like wood, have low melting points and are brittle, they have lower densities compared to metals making them lighter in weight.

Transition metals are found at the centre of the periodic table, they share the same qualities as metal but they have some other properties, one of the things that are different about these transition metals is that they can form more than ions.

Let's take a transition metal, Chromium, which can form 2+, 3+, and 6+ ions, these transition metals are often coloured, so if we take their liquid forms +2 would be blue, +3 would be green, and then +6 would be orange. 
Chromium is a catalyst, which increases the rate of a chemical reaction, without being in the reaction themselves. 

For example, iron is used in our bodies to harber processes, while nickel is used in the hydrogenation of Alkenes, which the alkenes are used in margarine.

The Modern Periodic Table

As you know everything on Earth is made out of specific combinations of atoms on the periodic table, you read it from left to right and top to bottom, the order of these atoms is not random, as the elements are arranged in increasing atomic number or the number of protons the element has. 

The periodic table was made in the 19th century by Dimitri Mendeleev

The periodic table has symbols each explaining what the element is, the two-letter symbol is the Nuclear or Elemental symbol like Na for sodium or Ca for calcium. And on the bottom left is the Atomic number which is how many protons the element has, and finally is the mass number which is the total amount of protons and electrons an element has. 

When Dimitri was plotting the table, he found a pattern, so instead of arranging the elements in a straight line.

He instead made verticle columns which he named periods every time the pattern repeated, each element in each period has similar properties and is called a group,  going from 1 at the leftmost, to 7, but the last group is dubbed group 0, named the noble gasses these are the most stable elements on the table. 
For example, Helium which has one shell, has two electrons and since they don't need to gain or lose electrons to be stable, so that makes them very stable.

Also, another thing to remember is that the block of metals between groups 2 and 3 doesn't have.

The reason why elements are grouped this way is because they have the same amount of elections in their outermost shell, and depending on the group and how many elections it has affects how the element reacts with other elements.

Using the group numbers you can figure out how many electrons they have in their outer shell, while every element has a different amount of electrons.
All group 1s have one electron in the outer shell, and group 2 has two in their outer shells.

Let's start with the Alkali metals, which are in group 1 since they have the same amount of electrons in their nutshells.
They share similar properties, for example, they all react violently with water.

Group 7, named Halogens, have seven electrons in their outer shells, and they get less reactive the lower you go.

 

History of the Atom

The first theory was the atomic theory, in 500 BC, which was that everything was made out of tiny particles that are separated by empty space, this idea was proposed by Democritus from ancient Greek.

Then the 1800s John Dalton said that objects were built out of spheres that make out all the elements.

After John Dalton, JJ Thomson made the "Plum pudding" model in 1897, which stated that what we would call atoms today, were not spheres but negatively charged particles, which are now named elections.
He said that 'atoms' are balls of positive charge with small amounts of negative charge.

Ernest Rutherford and his students found in 1909 that if they shot an 'Alpha' particle at a thin sheet of gold, it would pass right through if the plum pudding model was to be true, the alpha particle would have shot clean through the gold sheet.
But instead, some particles would deflect off the gold, and some would even be completely redirected the way they were coming from.

So Ernest and his students proposed the Nuclear theory, which stated that the atom was a compact nucleus which was positively charged, while the negative charge is more like a cloud around the nucleus, there was one thing that was weird about this model, as there is nothing stopping the 'cloud' of negative charge from charging into the centre of the nucleus collapsing the whole thing.

It was not until 1913 that Neils Bohr said that the electrons orbited around the nucleus in shells similar to planets around the sun the part where it orbits around the nucleus is very important.
As that is what keeps the atom from collapsing, Ernest once again found that there are small particles inside the nucleus that were giving positive charge, which we now know as Protons.

Then a person named James Chadwick provided evidence that there are neutral particles no named Newtrons along with the protons. 

  

Filtration, Evaporation & Crystallization

We can separate soluble and insoluble solids from liquids, by using Filters, Evaporation and Crystallization.

First, an insoluble solid is something like sand in water, since it doesn't dissolve is it is a mixture while if we have a liquid and put something soluble like sugar it will dissolve and it is called a solution the sugar being the solute and the water being solvent. 

Filters are usually used in cooking by using a sifter, but in chemistry, we use something called filter paper, which is paper with very small holes in it.
The holes in filter paper are so small that only water can pass through and most solids can't, even individual grains of salt or sugar to sand can't pass through.
Normally we cover a funnel with filter paper so we can easily pour water into the funnel and the filter paper filters it for us. 

A Solution is when there's a soluble solid, that mixes into a liquid, like salt, but if we want to separate the liquid and solid we have to use Evaporation because we can't use filter paper since the salt is already mixed with the water.

So if we want to extract sea salt, first we must put the seawater into a suspended dish, and then we heat up the liquid inside with fire or a bunsen burner, after a while you will notice that the water evaporates and what is left are crystals, in this case salt crystals.
One thing that's good about using evaporation is that it is a relatively fast way to remove the liquid from the solid.

Some solids will decompose when heated up, the heat causing the solid that we want from the evaporation process to be broken down into something that we don't really want.

For solids that we want to separate from liquids, but don't want to be broken down and decompose, we have to use a slower method named Crystallization, once again we must take the liquid and heat it up in a dish, but time we must make sure to heat it up more gently instead of quickly.
Instead of letting the crystals form and continuing to let the liquid heat up and decompose the solid that we want. We stop heating it after crystals form, and let it aside to cool, an more crystals will form because solids are less soluble at colder temperatures. 
Finally, we can use a funnel covered by filter paper and pour the liquid with crystal in it, filtering it and giving us the solid we need from the liquid. 

Balancing Chemical Equations

Chemical equations are very important for written Chemistry, for example, if we take Methane + Oxygen -> Carbon Dioxide + Water, the underlined words are products, while the non-underlined are not.

Now to write this as chemical symbols you would write it as:
c
the Ch4 is because there is 1 carbon and 4 hydrogen. For the O2 it is because O2 is 2 oxygens.
While the products CO2 + H2O, has the CO2 has 1 carbon and 2 oxygen, while H2O has 2 hydrogen and 1 oxygen. 

Now if you want to "balance" these equations, it is mainly done by trial and error, it is because you can't change the subscripts because it changes the whole element to a completely different one.
But we can change how many of the elements there can be, to balance the
Ch4 + O2  -> CO2 + H2O.

So if we look at the products, we might notice that there are 3 oxygen molecules compared to the 2 oxygen molecules on the reactants side. 
So to make the equation "balanced", we must match the number of oxygen atoms on both sides. So we give the O2 on the reactants a 2O2 instead so that both sides have 3 oxygen molecules. 

But you almost might notice that we did not give
1 1/2 molecules of oxygen, to "balance" the equation, that's because we can't give half an oxygen molecule we must stick to whole numbers when balancing.
Now what about the other side of the products, well we also need 1 more hydrogen and 2 more oxygen on the right so we add 2H2O, and these are now balanced.

  

Differences Between Compounds, Molecules & Mixtures

 Mainly elements fall into 3 categories, Molecules, Mixtures and Compounds.

Molecules refer to elements bonded via chemical bonds, a good example of this is Oxygen, which is bonded together so they are classified as a molecule, but these molecules can also be made of multiple different elements, such as water which is H20, others being Hydrogen, Chlorine and Carbon-dioxide. Molecules need 2 or more elements in order to be considered a molecule.

A Compound is made out of two elements held together by chemical bonds, for example, water is also considered a compound because it contains hydrogen and oxygen.
Along with carbon dioxide because it is made out of oxygen and hydrogen. But water, chlorine and hydrogen are not considered compounds because they only have one unique element.
Another thing about compounds is that they are found in the same proportions, so you wouldn't see a water compound with one more hydrogen. Water will always have two hydrogen atoms and one oxygen atom. And it is consistent and never changing.
Since it is consistent water will always be H2O. Now the smaller 2 is written in a "subscript" which signifies that the H in the water molecule is that there are two hydrogen atoms, and carbon dioxide is always going to be CO2, the 2 being that there are two oxygen atoms. 

Another element is H2SO4, which always has 2 Hydrogen (H2), one Sulfur (S), and four Oxygen (O4).
But for some elements, Calcium for example: Ca(OH)2, the calcium is made out of one Calcium atom (Ca), and two of OH or (OH)2. 
These atoms are actually very small as some atoms contain up to a billion atoms, like table salt or Sodium Chloride which has the elements NaCl.  
But unlike other atoms, sodium chloride has as large structure compared to other atoms, sodium chloride has an Ionic bond, and the NaCl or table salt is a 1:1 ratio, so that if there's a Na atom there is always a Cl atom.

Mixtures are substances that are not bonded together. So if we combine sodium chloride, oxygen, individual helium atoms, and carbon dioxide this would be considered a mixture, 

Elements, Isotopes and Relative Atomic Mass

The amount of protons tells us how heavy and what number it is assigned to in the periodic table, so Hydrogen is the lightest and has a single proton and electron.

Next on the line is Helium because it has 2 protons and 2 electrons. As you look at any periodic table, there are over 100 different elements some that act similar to each other but they are different. Copper and Tin are different elements, but they are both metals. 

The number at the bottom of most elements is the Atomic symbol, which is unique to every element, as it is the number of protons in the element, and elements cannot overlap in atomic numbers. 

If we take another element...Carbon its atomic number is 6, so every carbon atom should have 6 protons, if we take an atom with 3 protons it cannot be carbon but instead, it is Lithium.
Also the alphabetic letter on the element says its name so Li is Lithium, C for Carbon, but not all elements follow this naming scheme, a good example is Fe or Iron and Na which is Sodium.

Well if the number of protons determines the element, what about Neutrons, well neutrons vary between elements and even in the same element we call these kinds of elements Isotopes. The definition of an isotope is that
"They are different forms of each element that have the same number of protons but not neutrons."

If we take carbon, the most common version of carbon is Carbon 12 which has 6 protons, electrons and neutrons, while another form is Carbon 13, which has the normal 6 protons but has 7 neutrons and 6 electrons.

Something to keep in mind is that all isotopes alike elements have different masses, let's take copper for example.
Copper has two stable isotopes, copper 63 taking around 69.2% of all copper elements, and copper 65 has an abundance of 30.8%, when we are talking about the abundance of an isotope it means how common these isotopes are.
In a quiz or exam, you might see a question like: "Calculate the relative atomic mass to 1 decimal place".
For this equation, you will do "(the sum of all isotope abundance * mass) divided by the sum of abundance of all isotopes".
So lets take copper-63 which is 69.2% * 63 (copper 63), but for copper-65 it would be 30.8% * 65. Then we add both equasions (copper-63 + copper-65) then we add the isotope abundance of 69.2 + 30.8.

So the 69.2 * 63 is equal to 4359.6 and the 30.8 * 65 is equal to 2002, then you add them together to get 6361.69,  then we divide them by the 69.2 + 30.8 which is equal to 100. so we divide 63.6169 / 100. And we get 63.6169.
But the question wants it to be "Calculate the relative atomic mass to 1 decimal place", we will instead put 63.6 instead.

Atoms and Ions

Everything, non and living is made of small things named Atoms.

At the basic structure, an atom is a Nucleus surrounded by-elections which orbit around the Nucleus in rings called shells,
the nucleus of an atom is made out of two things Protons, and Neutrons, both having very similar weight, but electricians are nearly 2000 times lighter than protons or neutrons.

Protons have a +1 charge, while neutrons have no charge, so they are neutral, and electrons have a -1 charge.
The size of an atom depends on the type of element they are, but most are 0.1 nanometers in size, for example, the average size for a penny is 19.55mm, which is equal to 19,050,000 nanometers).
Most atoms are empty space because we measure the size of an atom starting from the nucleus to the outermost shell.

The nucleus is 10,000 times smaller than the size of the whole atom,
if an atom has the same number of Protons and Electrons, the atom thus, neutral.
But when an atom gains an election it is named a Negative Ion or Anion since there are more electrons than protons, this is called a -1 negative ion, and if you add another election it would be a -2 negative ion. 

Then if an atom has fewer electrons than protons (3 protons 2 electrons), it would be a +1 ion.
An atom on the periodic table is an Element, and each box on the periodic table has an element, each box is named a 'Nuclear symbol". 

Let's take two elements: Oxygen and Lithium, the Li and O on the box are the elemental symbols, then in the bottom left corner of the element is the Atomic number which tells us how many protons the atom has, so an Oxygen atom has 8 protons while a Lithium atom has 3.

The top number is the Mass number, which tells us the total amount of Protons and Neutrons the element has.
Now let's use a lithium atom for example, so a Li element or lithium will have a 7 as its mass number and a lithium atom has 3 protons, so if you do 7 - 3 protons, you get the number of neutrons a lithium atom has which is 5 neutrons. 

An oxygen atom has a mass number of 16, and its amount of protons is 8 so 16 - 8, is 8 so it has 8 neutrons. Or to get the amount of neutrons you do the mass number minus the atomic number.