Bonding - Ion Formation (A-Level Chemistry)
Ion Formation
Formation of Ions
Re-cap of Ions
- Ions are formed from atoms when electrons are transferred between them. A negative ion is formed if an atom gains an electron and a positive ion is formed if an atom loses an electron.
- Atoms form ions to gain a full outer shell of electrons like the noble gases. Atoms want to gain a full outer shell of electrons because this makes the atoms stable and unreactive like the noble gases which are inert.
- A lot of ions are formed from single atoms. When an ion is formed from a single atom, it means an electron is transferred between only one type of atom. E.g. Na+ is an ion formed from a single atom which is Sodium. It is formed when a sodium atom loses an electron.
- The group of the periodic table the element is in tells you how many outer shell electrons it has. E.g. a Group 1 element has 1 election in its outer shell. Group 2 elements have 2 outermost electrons. Group 6 have 6 outermost electrons and Group 7 have 7 outermost electrons.
- The group of the periodic table the element is in tells you which ion it will form. All the elements in one group of the periodic table have the same number of electrons in their outer shell. This means that all the elements in the same group will form an ion with the same charge as they all have to gain or lose the same number of electrons to achieve a full outer shell of electrons.
- Most transition metals will form more than one type of ion. The elements on the middle block of the periodic table have the particularity that they can lose a variable number of electrons from their outermost shell to form more than one type of ion. The exception to this are zinc and silver which only form one type of ion each: Zn+2 and Ag+ respectively
Compound Ions
- A compound ion is an ion formed from multiple atoms instead of single atoms. A compound ion is formed from multiple atoms. For this course, we will need to learn the following formulas of compound ions.
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