+ Electron Structure Noadswood Science, 2012

+ Electron Structure To be able to represent the electron structure of atoms Thursday, February 11, 2016

+ Reactivity Some metals are extremely reactive, whilst others are not – the reactivity series shows how reactive metals are… Potassium Sodium Calcium Magnesium Aluminium (Carbon) Zinc Iron Lead (Hydrogen) Copper Silver Gold Platinum

+ Reactivity Compare the reactivity series to where the elements are found within the periodic table – what relationship is there?

+ Electron Structure & Reactivity There is a definite pattern between the placement of a metal on the periodic table and how reactive it is – the most reactive metals are located in groups I and II, with the least reactive metals being within the transition metals, placed in the centre of the periodic table, between groups II and III – they are generally hard and dense, and less reactive than the alkali metals

+ Reactivity – Very Reactive The electron structure of an atom affects how reactive it is – a shell with just one electron in is it keen to ‘get rid’ of this so they have a full outer shell Elements within group I (lithium, sodium, potassium etc…) and group II (magnesium, calcium, strontium etc…) have just one or two electrons to ‘get rid of’ before they have a full outer shell, and as such are extremely reactive The most reactive metals are found within group I and II

+ Reactivity – Not Reactive Electron structure of an atom affects how reactive it is – a shell with three of four electrons will find it very difficult to gain / loose enough electrons to have a full outer shell Elements within group III and group IV (including the transition metals such as zinc, silver and gold) have lots of electrons to gain / lose before they have a full outer shell, and as such as quite un-reactive This is why metals such as gold can be found as ‘pure’ – they are so un-reactive that they have not reacted with other chemicals for billions of years

+ Electron Structure Electrons are arranged in different shells around the nucleus The innermost shell - or lowest energy level - is filled first Each succeeding shell can only hold a certain number of electrons before it becomes full - the innermost shell can hold a maximum of two electrons, the second shell a maximum of eight, and so on... Energy Level (Shell) Maximum No. Electrons First2 Second8 Third8 Fourth18

+ Shells Electrons which orbit the nucleus of an atom occupy specific shells – the follow some specific rules: - Electrons always occupy shells (energy levels) The lowest energy levels are always filled up first Only a certain number of electrons are allowed in each shell (1 st shell = 2; 2 nd shell = 8; 3 rd shell = 8; 4 th shell = 18) In most atoms the outer shell is not full, making them want to react

+ Electron Structure The electronic structure of an atom is a description of how the electrons are arranged - you need to be able to describe the electronic structure of the first 20 elements in the periodic table... The first 20 elements in the periodic table run from hydrogen to calcium

+ Electron Structure The periodic table can be used to work out an electronic structure: - 1. Find the element in the periodic table 2. Work out which period it is in, and draw that number of circles around the nucleus 3. Work out which group the element is in and draw that number of electrons in the outer circle - with eight for Group 0 elements (except helium) 4. Fill the other circles with electrons (2 in the first, 8 in the second and third, and 18 in the fourth) 5. Finally, count your electrons and check that they equal the atomic number

+ Lithium For example, work out the atomic structure of Lithium...

+ Lithium Lithium - 2nd period so it has 2 circles drawn around it and in group 1 so it has 1 electrons in the outer shell...

+ Lithium Lithium (Li) - 2,1 (three electrons (2 in shell 1 and 1 in shell 2))

+ Examples Draw the following atoms and write their electron numbers... Fluorine Neon Sodium Calcium

+ Examples Fluorine 2,7 Neon 2,8 Sodium 2,8,1 Calcium 2,8,8,2

+ Position Electrons occupying shells around the nucleus is the ‘cause’ of all underlying chemistry When elements react their atoms join with other atoms forming compounds – this involves giving, taking, and sharing of electrons What link is there between the electron structure and the elements position within the periodic table?

+ Position There is a link between an atom's electronic structure and its position in the periodic table – an atom's electronic structure can be worked out from its place in the periodic table…

+ Position Atoms in group I have 1 electron in the outer shell Atoms in group II have 2 electrons in the outer shell Atoms in group III have 3 electrons in the outer shell etc… Atoms in group VIII have a full outer shell