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History of Atoms

John.D discovered atom

J.J Thomson all atoms for same element are the same

Ernest Rutherford discovered nucleus

Model of atom changed over time to explain it

Structure of Atom

Nucleus surrounded by neg charged electrons

Nucleus made of pos charged protons and neutrons (no charge)

Atom has no overall charge

Relative mass of electron is 0 others are 1

Elements and Compounds

Elements are 1 type of atom

Over 100

Compound are 2 or more elements chemically combined

Mass and Atomic Number

Mass number top

Total number of pro and neu

Atomic number bottom

Total number of protons

mass take atomic= number of neutrons

Protons=atomic number

Electrons=protons

Period number- how many shells used

Group number- how many electrons in outer shell

Elements arranged by increasing atomic number

Isotopes

Atoms of same element, same atomic number, different mass number so different number of neutrons

Carbon has 3 isotopes (12,13, 14)

Electron configuration

how electrons are arranged

2,8,8

atomic number=number of electrons

Ions

Charged atoms

If atom loses electrons, positive ion

If atom gains electrons, negative ion

Ionic Bonding

Metal atom loses outer shell, becomes positive

Non-metal gains electrons to fill outer shell, becomes negative (forms stable octet)

They are attracted

E.G.sodium chloride and magnesium oxide- high melting points, only conduct in solution and when molten, can dissolve in water

Structure and Physical properties

Sodium chloride and magnesium oxide form Giant ionic lattices- pos and neg ions strongly attracted

Ions in solution are free to move so can conduct

Magnesium oxide has higher melting point

Making Ionic Compounds

If an atom has 1 electron on outer shell and the other needs 1 electron.It transfers making atoms ions.(The atoms become charged.

If an atom has 1 electron on outer shell, but other atom needs 2 another of the first atom is needed.

If an atom has 2 electrons on outer shell and the other only needs one, another atom of the second is needed.

Groups

Groups

Vertical group on periodic table

Have same number electrons on outer shell as group number

Group 0 has full outer shell

Similar chemical properties

Periods

Horizontal row of periodic table

Same number as elements used shells

Electronic Structure

Can find elements position on periodic table using group and row

Bonding

Covalent-all non metals

Ionic- metals and non metals

Metallic- all metals

Covalent Bonding

Non metals share pairs of electrons

E.g. Water- H2O liquid at room temp, doesn't conduct, low melting point

Carbon dioxide- CO2, dosen't conduct, gas at room temp and low melting point

Weak intermolecular forces so low melting point, no free electrons

Representing Molecules

H2- share electrons

H-H

Development of the Periodic Table

Dobereiner- law of triads, elements with similar properties, did not work

John Newlands- first "periodic table" included compounds as he thought they were elements, Law of Octaves

Mendeleev- modern periodic table, left gaps in, but made predictions and was later found to be correct

Alkali Metals

Group 1 elements

Alkali metals stored under oil as reactive with air and water

Reactions with water

Alkalis react with water produce a hydroxide and hydrogen. Produce alkaline solution.This is why they are called alkali metals

Lithium reacts gently

Sodium more vigorously

Potassium produces lilac flame

Flame Tests

Sodium yellow

Potassium lilac

Lithium Red

Nichrome wire dipped in water, then in solid compound, then in flame

Properties of Alkali Metals

Rubidium reacts with water-fast, violent and exothermic

Density increases as go down group 1

Caesium- greatest density, lowest melting and boiling point

Trends in group 1

Have similar properties

Lose one electron from outer shell as react

Positive ion made

Get more reactive down the group as outer shell gets further away from pos nucleus. Makes losing electron easier.

Oxidation-electron lost

Group 7-halogens

Non metals

At room temp: chlorine green gas, bromine orange liquid, iodine grey solid

Iodine used to sterilise wounds

Chlorine sterile water, make plastic and pesticides

React vigorously with alkali metals, make halides

Replacement Reactions

Reactivity of group 7 decreases as you go down

More reactive reactive halogen will displace less reactive halogen

Chlorine displace bromides and iodide

Bromine displace iodides

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