C1

Atoms and Elements

Atoms

PEN

Atoms contain:

• Protons- Relative Charge = +1 | Relative Mass = 1 | LOCATION = Nucleus

• Neutrons - Charge = 0 | Relative mas = 1 | Location = Nucleus

• Electrons- Charge = -1 | Mass = (negligible) | Location = Electron shells

• Same amount of protons as electrons, only in ATOMS (different in ions)

• Atomic number = Number of protons

• Atomic Mass number = Number of protons and neutrons combined

Structure

The structure of an atom consists of:

• The nucleus- A concentrated point at the centre of the atom of all its mass, protons, neutrons and positive charge.

• The electrons- Shells that the electrons orbit the nucleus the volume of which determines the size of the atom, (mostly empty space), virtually no mass

Differentiations

Now of course there’s lots of different variations of atoms, this comes in the form of:

• Ions- These are atoms the same number of protons different number of electrons.

• Isotopes- Same number of protons different number of neutrons

• Elements - A pure substance that is only made up of one type of atom

• Compounds-A substance formed from two or more elements reacting

• Allotropes - An element arranged in a different structure to give it different properties

Stats

Now for the annoying numbers:

• Atoms have a radius of roughly 0.1 nanometres (1 × 10^-10 m)

• The nucleus has a radius of roughly 1 × 10^-14 m, so 10,000 times smaller than the whole atom

Elements

Elements - A pure substance that is only made up of one type of atom

they have symbols blah blah blah

Isotopes

• Isotopes- Elements with the same number of protons different number of neutrons

• As a result of this they have a different relative atomic mass

• however they still are the same element by principal

• Relative atomic mass of an element therefore is calculated taking into account each isotopes abundancies

  ---

Compounds and equations

Compounds

• Compounds-A substance formed from two or more elements reacting

• Compounds are held together in fixed proportions

• They are held together by chemical bond

• These Bonds are made by the sharing or taking of an electron

• These bonds are usually strong requiring chemical reactions to break

How thing react: Ionic bonds

• An ionic bond is defined by- electrostatic forces of attraction between oppositely charged ions arranges in a giant ionic lattice

• A compound consisting of a metal and a non metal is an ionic compound

• The metals lose electrons to form positive ions

• and the non-metals gain electrons to form negative ions

• These opposite charges are strongly attracted towards creating ionic bonds

How thing react: covalent bonds

• A covalent bond is a bond formed when a pair of electrons is shared between two atoms

• These bond usually take place between non-metals

• Their compounds are usually totally different from the elements e.g. water is made of gasses

Symbols- The actual hard part

Ok so the thing is that compound symbols:

• Have big numbers multiply the entire compound by that much

• These big numbers represent the molar ratio

• Small numbers only times one element in the compound by n

• Small numbers next to the brackets multiply everything in the brackets by n

Oh yeah, and remember this for me lil nga:

• Carbon dioxide → Co₂

• Ammonia → NH₃

• Water → H₂O

• Sodium chloride → NaCl

• Carbon monoxide → CO

• Hydrochloric acid → HCL

• Calcium chloride- → CaCl₂

• Sodium chloride → Na₂CO₃

• Sulfuric acid → H₂SO₂

• Hydrogen → H₂

• Phosphoric acid → H₂So₄

• Sulphate → SO_{4 ^(-2)}

• Nitrate → NO_{3 ^(-1)}

• phosphate →PO_4^(-3

• Hydroxide → OH^(-1)

Equations

Remember that you have to have the same amount if reactants as products

You can: Show chemical equations with words or symbols:

Words are so much easier, considering you don’t have to factor i- Oh wait you haven’t learned that yet L e.g:

Methane + oxygen → Carbon dioxide + water

Symbol equations:

These are the shorthand way if writing chemical equations using just their: Chemical symbols, Molar ratios, Ionic charge, Bonding configuration, oh no. e.g.

Magnesium + Oxygen → magnesium oxide

2M + O₂ → 2MgO

Symbol equations must be balanced:

This is because as matter can neither be created nor destroyed, each element must be represented in equal amounts on both sides s both the products and the reactants.

When balancing an equation:

• You must not Change the small numbers as that changes the away the elements are bonded

• This means you can only change the large numbers and their molar ratio

• Until there is the same amount of Products as reactants

• This means that if there was 5 gold reactant atoms and 3 oxygen reactant atoms

• There will be 5 gold product atoms, and 3 oxygen product atoms

The modern periodic table

Order

The periodic table is ordered in multiple ways

• in order of proton number, going across from left to right

• Non- metals on the right, metals on the left

• Vertical columns are groups (that’s on the y axis)

• Each group has the same number of electrons on their outer most shell

• The group number increases going from left to right

• This corresponds with their overall group number

• E.g. group 1 has 1 electron on its outermost shell etc.

• Each row going across is a period

• Each period has one more shell of electrons

• The properties of these elements can be predicted based off of these factor

• a

  

The rule of nuclear attraction

The further away electrons are from the nucleus the less attraction there is. This means on the outermost shell is the weakest nuclear attraction. For lower grouped elements this is a good thing because it means it makes it much easier to lose their electrons and gain a full outermost shell. Which is an application of this rule of nuclear attraction which happens in the inverse for high group elements

Metals and nonmetals

What are they?

• Metals are elements which can form positive ions.

• Most elements are metals

• Non-metals don’t usually form positive ions

How things react

• Atoms usually react in order to form a full outer shell

• whether it be through gaining losing or sharing electrons

Mixtures and separation

A mixture is a combination 2 elements or compounds that are not chemical joined together

Solvent- a liquid that can dissolve certain solutions

Solute- a substance dissolved in a solvent

Solution- the mixture of the solvent and solute

Aqueous- The state a solute is in when it is dissolved in a solute

Soluble- can dissolve in solvent e.g. liquid

Insoluble- Something that can’t be dissolved by a substance

They can be separated by:

Chromatography

1. Draw a line near the bottom of the paper (as pencil marks are insoluble)

2. Add a spot of ink to the line

3. Place it in a beaker with a solvent (e.g. water or ethanol)

4. Make sure the ink isn’t touching the solvent

5. Place a lid on top of the container to stop it from evaporating

6. The water moves up the paper

7. Different dyes move at different rates so they will separate out as they move up

8. Take it out once the water has almost reached the top

9. And the finished result: A chromatogram

Filtration

Use this to filter and insoluble solvent from a liquid e.g. sand from water

• Its done by using filter paper folded into a cone

• Connecting it to a funnel

• And placing a beaker under it

Evaporation e.g. (Salt and water)

1. Pour solution into evaporating dish

2. Heat slowly until the solution get concentrated enough to form crystals

3. Keep heating evaporating dish until all you have left are crystals

This can only be used when the salt doesn’t decompose when heated

Crystallisation e.g. (Salt and water)

1. Pour solution into evaporating dish

2. Heat slowly until the solution get concentrated enough to start forming crystals

3. Let the solution to cool down slowly, during this time the solution will form crystals

4. Filter out the crystals and let them dry in a warm place e.g. oven or desiccator

Filtration and crystallisation can be used to separate rock salt, a mixture of sand and salt

• Grind the rock salt down

• add water

• Stir it

• Filter it

• Crystallise it

Simple distillation Distillation: 2 liquids (far boiling points)

1. The solution is heated at a particular heat,

2. The part with the lowest boiling point is heated first

3. It travels into a condensation tube

4. Where cold water flows through adjacent tubes to keep it cool

5. Then the condensed water is collected in a beaker next to the tube

This only works for liquids with a boiling points far away from each other

Fractional distillation: Close boiling points e.g. oil refinery

1. The only difference is a fractionating column

2. This is a bunch of convoluted tubed which slow gasses down

3. By the time the temperature reaches the lowest boiling point

4. the corresponding liquid will already be at the top

5. And whilst the other liquids may start rising

6. They will cool down before they reach the top

7. Ensuring only one substance distillates at a time