Chemistry- Atomic structure and The Periodic Table

History of the atom

Timeline

Democritus 460-370 BC

democritus

  • Tiny particles even in different shapes
  • He called them atomos
  • However Aristotle disagreed saying that all matter is made of water, fire, earth and wind

John Dalton 1766-1844

  • In 1808 John Dalton saw that common things broke down into the same elements
  • Different size and mass

J.J Thomson 1856-1940

democritus

  • Atoms packed full of spheres of positive matter embedded with negatively charged electrons

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Earnest Rutherford 1871-1957

  • He did an experiment showing there is space for particles to pass through
  • However some particles bounced back showing there was a nucleus

Rutherford_atomic_planetary_model

Niels Bohr 1885-1962

  • This model shows the electrons orbiting the nucleus

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Werner Heisenberg 1901-1976

  • He challenged Bohr saying it was impossible to know the speed and the exact whereabouts of an electron

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  • Also known as the Plum Pudding model
  • First speculation
  • Found out that an atom can not be created or destroyed
  • This was the discovery of the electron
  • He won a nobel prize, however this model did not stay long
  • He found this by using earlier works from Planck and Einstein
  • Discovered electrons orbit nucleus at fixed energy levels
  • Able to jump from one shell to another

Atoms- An atom is the smallest part of an element that can exist on its own

Elements- substance that contains only 1 type of atoms

Molecules- A molecule is where 2 or more atoms are chemically bonded together

Compound- Atoms of 2 or more different elements chemically bonded together

Particle

Mass

Charge

Location

Neutron

Proton

Electron

1

+1

Nucleus

1

0

Nucleus

very small

-1

orbiting around the Nucleus

The atom

The number of electrons = The number of protons

The charge of electrons = The charge of protons

Number of electrons in each shell

Shell 1 - 2

Shell 2 - 8

Shell 3 - 8

Shell 4 - 2

Number of Protons + Number of Neutrons = Mass number

Number of Protons = Atomic Number

Number of neutrons = mass number - atomic number

Isotopes- Atoms of the same element with the same number of electrons and protons but different number of neutrons

Ions

An ion = a charged particle

When atoms gain and lose electrons they develop a charge

Loose electrons = positively charged

Gain electrons = negatively charged

They are charged because the amount of electrons is not equal to the amount of protons

With positive ions, The charge = the group number

With negative ions, the charge = the group number - 8

Most types of metals form positive ions

Most types of non-metals form negative ions

Group 1 metals

The metals

Li - Lithium

Na - Sodium

K - Potassium

Rb - Rubidium

Cs - Caesium

Fr - Francium

Trends

  • The further down the column the more reactive they get
  • All are white crystalline solids
  • The melting points decrease as you go down the column
  • They are all colourless solutions
  • They are all electrolyes
  • They all have high melting points and high boiling points

All the metals in Group 1 have 1 electron on the outer shell meaning they all have 1+ charge, this means they are IONIC

  • They all have 1 electron on the outer shell

Another name for them is ALKALI METALS

Water mixed with alkali metals causes an explosion

Li, Na, K

have to be stored in oil

they are soft and when exposed to air in a matter of seconds you can see it tarnishes showing a reaction

because of how reactive they are

Sodium + Water

Na + H2O = NaO + H2

It floats on the water and fizzes

Potassium + Water

K + H2O = KOH + H2

It fizzes and gives off a purple flame also the gas ignites on its own

Rubidium + Water

Rb + H2O = RbO + H2

It explodes giving off a cloud of gas this happens immediately

Caesium + Water

Cs + H2O = CsOH + H2

It immediately gives off a big explosion

Francium is even more reactive, it is dangerous

Group 7

The non-metals

F - Florine

Cl - Chlorine

Br - Bromine

I - Iodine

At - Astatine

Also known as the halogens

They all have 7 electrons in the outer shell forming a 1- ion when they react

Trends

  • The melting and boiling points increase as you go down the column
  • They all go around in diatomic pairs

They react with other non- metals and form covalent bonds

They react with metals to form ionic bonds

  • They have all typical non-metal properies

Low melting points

Low boiling points

Brittle

Dull

They do not conduct electricity

Do not conduct heat

Fluorine - pale yellow - gas

Chlorine - yellow, green - gas

Bromine - reddish brown - liquid

Iodine - violet - solid

These are all types of structure covalent

Group 0

The non-metals

He - Helium

Ne - Neon

Ar - Argon

Kr - Krypton

Xe - Xenon

Rn - Radon

They are also known as Noble Gases

Because they have filled outer shells, there is no chemical reaction as there is no way to gain or lose electrons

Their electron structure is special as they all have filled outer shells

Helium - 2 - Gas - White, orange

Neon - 2,8 - Gas - Red, orange

Argon - 2,8,8 - Gas - Violet

Krypton - 2,8,8,8 - Gas - Grey

Xenon - 2,8,8,8,8 - Gas - Grey, blue

Radon - 2,8,8,8,8,8 - Gas - Colourless

Transition Metals

They are the large block of elements between group 2 and 3

Trends

  • They have the highest melting points and boiling points
  • They have higher densities
  • They are much stronger and harder
  • They are all metals
  • They have metallic properties

They are much LESS REACTIVE

They have more uses than Group 1

Transition metals have special properties as well

  • They form different charges e.g iron (II) ions, Fe 2+
  • They form coloured compounds e.g copper (III) sulfate is blue
  • They are useful catalysts e.g iron in the haber process and nickel in the hydrogenation of fats

Ionic Bonds - When group 1 metals react with non-metals

Covalent Bonds - A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms

Perfect paragraph to explain the reaction between Sodium and Chlorine

The outer electron from the sodium atom is transferred to the outer shell of the chlorine atom

To form a sodium ion (Na+) and a chlorine ion (Cl-)

Both ions have filled outer shells

As these ions have opposite charges so they attract each other

This is called an ionic bond