Chemistry : C1

Define an element

A substance made up of atoms that all have the same number of protons

Define an isotope

Different forms of the same element which have the same number of protons but different number of neutrons

How can you identify an isotope?

It will have the same atomic number as the element but different mass number

What are compounds and how are they created?

Substances formed from two or more elements chemically reacting to form chemical bonds through the sharing of electrons

What is ionic bonding (simple definition)?

When bonding takes place between a metal and non-metal.

The metal atoms lose electrons to form positive ions

The non-metal atoms gain electrons to make negative ions

The nucleus of an atoms is made up of —- and has a — charge

Protons and neutrons

Positive charge

— orbit the nucleus in — and have a — charge

Electrons

In shells

Negative charge

What is the charge of an atoms?

Neutral/no charge

Same number of protons and neutrons

What is each number known as and what does it show?

TOP = Atomic number = shows the number of protons the atom/ion has (equal to number of electrons)

BOTTOM = Mass number = shows the total number of protons and neutrons in the atom

What’s the properties of metals?

Metals react to form positive ions, non-metals do not

Metals are strong but malleable

Metals are good heat and electricity conductors

Metals have high boiling and melting points

What are the properties of non-metals?

Non-metals do not react to form positive ions

Dull-looking

Brittle

Not always solid at room temperature

Lower density

Less or no electricity conductivity

What is relative atomic mass?

An average mass of isotope abundances used instead of mass number for isotopes

What is the formula for relative atomic mass?

Ar = (mass of isotope 1 x % abundance of isotope 1) + (mass of isotope 2 x % abundance of isotope 2)

————————————————————————————————————————————————————

Abundance of isotope 1 + abundance of isotope 2 (or use 100)

What does filtration separate?

To separate an insoluble (can not dissolve in a liquid) solid from a liquid mixture.

How do you carry out filtration?

On top of a beaker place a funnel lined with filter paper in a cone shape

Pour the liquid mixture through the funnel

What does evaporation separate?

To separate soluble solids that dont decompose when heated from solutions

How do you use evaporation to separate a mixture?

Pour solution into an evaporating dish and slowly heat

The solvent evaporates as crystals begin to form

Keep heating until only dry crystals remain

What does crystallisation separate?

Separating soluble solids that do decompose decompose from solutions

How is crystallisation used to separate mixtures?

Pour mixture into an evaporating dish and slowly heat

Let some of it evaporate

When crystals begin to form, take off heat

Filter crystals our and leave in a warm place to dry

What are mixtures?

Elements or compounds mixed together with no chemical bonds that can be separated

How do you carry out paper chromatography?

• Draw a pencil (as pencil is insoluble and wont dissolve) line around 1cm from the bottom of a sheet of filter paper

• Fill a beaker with solvent (water) to the point where the line on the filter paper is just above the water surface

• Add a dot of ink along the line and place the sheet into the solvent - make sure the ink is not touching the solvent

• Place a lid on the beaker to prevent evaporation

• Leave an allow each ink to move up and separate

• When the solvent has nearly reached the top, leave the chromatogram to dry

How is simple distillation used to separate solvents?

The solution is heated and the part with the highest boiling point evaporates first

The vapour cools, condenses and is collected through the condenser into a beaker

The rest of the solution remains in the flask

If more than 2 mixtures repeat, increasing the heat each time

What does simple distillation separate?

Mixtures of liquids with different boiling points

How do you carry out fractional distillation?

Set up a flask connected to a fractionating column, condenser and connect to test tubes

Place the mixture into the flask and heat it

All the different liquids have different boiling points so will evaporate at different temperatures

The lowest BP will reach the top of the column first and condense

The higher the BP the liquids have = the higher they go up the flask

Repeat until all liquids have condensed

What is fractional distillation used to separate?

Mixtures of substances with varying boiling points

How can rock salts be separate? [pratical]

Bring the mixture to make sure salt crystals are small

Put the mixture into hot water and stir - the salt will dissolve and sand wont

Filter the mixture and the sand will collect on the paper (filtration) and salt passes through

Evaporate the water from the salt to form crystals (evaporation)

What determines how many electrons an atom/isotope has?

The atomic number which shows the number of protons which is equivalent to the number of electrons

How many electrons can be in each shell?

Shell 1 = 2

Shell 2 = 8

Shell 3 = 8

What do atoms/ions intend to do?

Gain or lose electrons to stabilise the outer shell

What are group 0 elements known as?

Noble gases

What are the properties of group 0 elements?

• Unreactive as they have a full outer shell

• Single atoms - not bonded

• Non-flammable

• Colourless at room temperature

• As you go down the group boiling points increases (due to greater intermolecular forces)

• As you go down the group relative atomic mass increases

What are group 7 elements known as?

Halogens

What are the properties of group 7 elements?

• Coloured non-metal vapours

• Exist as pairs of atoms (diatomic)

• All have 7 electrons in outer shell

• As you go down the group reactivity decreases (harder to gain electrons)

• As you go down the group higher melting and boiling points

• As you down the group relative atomic mass increases

How do group 7s react with non-metals?

They form covalent bonds to share electrons between the non-metal and non-metal (C2 for full explanation)

How do group 7s react with metals?

What is the formula?

They form ionic structures

Metal + halide = metal halide

What happens when group 7s react with hydrogen? (Formula)

Hydrogen + halogen = hydrogen halide

What happens when halogens react with a salt?

A more reactive halogen displaces a less reactive salt

What are group 1 metals known as?

Alkali Metals

What are the properties of alkali metals?

• One electron in the outer shell so are very reactive

• Soft

• Low density

• Increasing reactivity down the group

• Lowered melting and boiling points down the group

• Higher relative atomic mass down the group

Why do alkali metals increase in reactivity down the group?

The outer electron is more easily lost as the nucleus is further away so has less control

What happens when group 1 metals react with non-metals?

An ionic compound is formed

What happens when group 1 metals react with Water? (Formula)

Metal + water = metal hydroxide + hydrogen

What happens when group 1 metals react with Chlorine? (Formula)

Metal + Caroline = metal chloride

What happens when group 1 metals react with Oxygen? (Formula)

Metal + oxygen = metal oxide

How was the early periodic table arranged?

Who changed it?

How was it changed?

In order of atomic weight - their properties were not taken into account

Dimitri Mendeleev

He put elements in order of atomic weight while taking their properties into account to group them. He also left space for new elements.

How is the modern periodic table arranged?

In order of increasing atomic number with metals on the left and non-metals on the right

Elements with similar properties form columns vertically called groups

What do groups in the table represent?

The number of atoms in the outer shell and their reactivity

E.g. group 2 = 2 electrons in the outer shell

Who were the 5 scientists that contributed to the atom?

What did the model look like?

What did they think?

1. Dalton = solid spheres = tiny spheres that can’t be divided

2. JJ Thompson = plum pudding model = ball of positive charge with embedded electrons

3. Rutherford = positive central nucleus surrounded by ring of electrons

4. Bohr = electrons orbit nucleus in shells

5. Chadwick = discovered neutrons in nucleus