Chemistry 1: Atomic structure and the periodic table Electronic Structure

Atoms are ny, too small to see. They have a radius of 0.1 nanometres ( 1 x 10 –10 m) Atoms  1st shell– Lowest energy level and can hold 2 electrons Atoms have no charge because they have the same number of protons and electrons.  2nd shell– Energy level can hold up to 8 electrons Electron

Proton  3rd shell onwards– Can hold up to 8 electrons.

Nucleus Neutron Electron structure and the periodic table Elements in the same group have the same number of electrons on their outer shell. Electron Orbit around nucleus in Mass Number : shells protons + neutrons Proton number = Electron Number Proton Found in the nucleus Atomic number: Number of neutrons=

Neutron Found in the nucleus Protons Mass number—Atomic number

An ion is an atom that has lost or gained electrons. An isotope is an atom that has the same number Ions Isotopes of protons but a different number of neutrons. In an ion the number of protons is not equal to the number of electrons so the atom has an overall They have the same atomic number but different atomic mass numbers. charge. This can either be posive or negave.

Relative atomic mass (Ar) Relave atomic = sum of (isotope abundance x isotope mass number)

Mass (Ar) sum of abundance of all the isotopes An average mass of an element that has a number of different isotopes.

Chemical Equations Balancing equaons:  There must always be the same number of atoms on Chemical reacons are shown using: both sides of a symbol equaon.

 Word equaons Magnesium + Oxygen Magnesium Oxide  Atoms can’t just disappear. (reactants) (product)

 Symbol equaons—Show the atoms on both sides  You balance equaons by pung numbers in front of

2Mg + O2 2MgO the number. History of the atom Ideas about atoms have change over me. Compounds ‐ Have a fixed composion Mixtures ‐ No fixed composion Plum pudding model Rutherford’s nuclear model Bohr’s model ‐ Can be separated by a ‐ Can be separated by physical

An atom was a ball of posive Electrons orbing the nucleus Electrons orbit the chemical reacon means charge with electrons which contains very dense nucleus at set distances ‐ Chemical bonds between ‐ No chemical bonds between scaered in the ball. posively charged protons. in fixed energy levels (shells). atoms atoms

Separating Mixtures

Filtraon Evaporaon

Separates insoluble solids from liquids. Used to separate a soluble salt from a soluon.

‐ Put filter paper in a funnel and pour the ‐ Heat the soluon unl the solvent evaporates.

The Periodic table The arrangement of the periodic table has changed. soluon through it. The liquid passes through and the solid is caught in the filter paper. Early 1800s Crystallisaon

 Arranged my relave atomic mass. Used to separate a soluble salt from a soluon.

 Sciensts had not yet discovered proton, neutrons or electrons. ‐ Heat the soluon and then leave  There were gaps for missing elements that had not been found yet.

Dimitri Mendeleev Disllaon Paper chromatography You will need to  Ordered mainly by atomic mass. Used to separate liquid from a soluon. Can be used to separate different dyes in an ink. know the first 20  Elements with similar properes in the same group. element names Heat soluon and the part with the lowest boiling ‐ Compounds are dissolved by using filter paper and point evaporates and is condensed back into a liquid. a solvent, in which the compounds are placed.  Gaps le for elements that hadn’t been found yet. and their symbols

Modern Day Fraconal Disllaon  In order of increasing atomic mass. Used to separate a mixture of  Repeang paerns in the properes of the liquids from a soluon. elements. Group 1– Alkali metals Li Group 7– Halogens Group 0– Noble gases He  Metals are on the le and non– metals are on the right. ‐ One electron on outer shell Na ‐ Seven electrons on outer shell F ‐ Eight electrons on outer shell Ne K Cl Ar Properes of metals ‐ Ducle ‐ Malleable Properes of non‐ metals ‐ Brile ‐ Very reacve ‐ Less reacve down the group ‐ Unreacve as they have a full Rb Br Kr ‐ High melng and boiling point ‐ Insulators of heat and electricity Reacvity increases down ‐ Higher melng and boiling outer shell and are stable Cs I Xe ‐ Conduct heat ‐ Conduct electricity ‐ Not always solids ‐ lower density points down the group ‐ Colourless gases the group. Fr At Rn