Edexcel Chemistry Additional Science Revision

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  • Created on: 29-03-15 21:12

Additional Science Revision

CHEMISTRY

TOPIC 1;

Atoms;

-the nucleus contains protons and neutrons

-the nucleus is an overall positive charge because protons are positively charged and neutrons have no charge

-the nucleus is very small compared to the overall size of the atom

-the electrons have a negative charge

-electrons and protons have equal but opposite charges

-the number of protons is always equal to the number of electrons in an atom

PARTICLE

RELATIVE MASS

RELATIVE CHARGE

Proton

1

+1

Neutron

1

0

Electron

1/2000

-1

 

 

Electron Shells;

-only a certain number of electrons are allowed in each shell

-1st shell = 2      2nd shell = 8       3rd shell = 8

-Electronic configuration is the way in which electrons are arranged in an atom

-electronic configurations can be worked out using atomic numbers. For example, the atomic number of Sodium is 11. This means that there are 11 protons and also 11 electrons. To fill the shell you have:

2 electrons fitting the first shell (leaving 9 more)

9 electrons fitting the 2nd shell (leaving 1 more)

And 1 electron filling the 3rd shell (leaving none)

-the number of occupied shells is the same as the period number. Apart from elements in group 0 (which all have fill outer shells), the number of outer electrons is the same as the group number. For example the electronic configuration of Sodium is 2.8.1 therefore it shows that Sodium is in the third period and in group 1

Elements; (copper, aluminium, iron, oxygen, nitrogen)

-consist of one type of atom only

-each element has an atomic number and a mass number

-the atomic number says how many protons there are in an atom and how many electrons there are because an atom has the same number of electrons as protons

-the mass number is the total number of protons and neutrons in the nucleus

-to find the number of neutrons in an atom, just subtract the atomic number from the mass number

 

Isotopes and Relative Atomic Mass;

-Isotopes are different atomic forms of the same element, which have the same number of protons but different numbers of neutrons

-the existence of isotopes results in some relative atomic masses not being whole numbers

-they must have the same number of protons but different mass numbers, otherwise they would be different elements altogether

-The relative atomic mass of an element (Ar) is an average value for the isotopes of the element

 

Periodic Table;

-elements are in order of increasing atomic mass

-in 1869, Dmitri Mendeleev arranged 50+ known elements according to their properties and the properties of their compounds to make a table of elements

-the gaps in his table predicted the properties of undiscovered elements

-arranged the elements known at the time in a periodic table by using properties of these elements and their compounds

-metals and non-metals are on opposite sides of the periodic table

-the period number is the same as

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