Anions are ions with a negative charge, while cations are ions with a positive charge. The attraction between these ions are called the electrostatic attraction.
4.1.2 Describe how ions can be formed as a result of electron transfer
An ion is a charged particle. Ions form from atoms or from groups of atoms by loss or gain of one or more electron. All particles want a stable electron configuration isoelectronic to the noble gases.
When an atom loses electrons it forms a positive ion, also called a cation.
When an atom gains electrons it forms a negative ion, also called a anion.
The number of charges on the ion formed is equal to the number of electrons lost or gained.
4.1.3 Deduce which ions will be formed when elements in group 1, 2 and 3 lose electrons
Group 1 metals will form Cations with 1+ charge
Group 2 metals will form Cations with 2+ charge
Group 3 metals will form Cations with 3+ charge
This is because that is how many electrons required to lose for a full outer electron shell.
4.1.4 Deduce which ions will be formed when elements in group 5, 6 and 7 gains electrons
Group 5 non-metals will form Anions with 1- charge
Group 6 non-metals will form Anions with 2- charge
Group 7 non-metals will form Anions with 3- charge
This is because that is how many electrons required to lose for a full outer electron shell.
4.1.5 State that transition elements can form more than one ions
Transition elements can form more than one ions. Iron ions can exist either as 2+ or 3+. This metal was actually used in the syllabus so it is recommended to use it.
4.1.6 Predict whether a compound of two elements would be ionic from the position of the elements in the periodic table or from their electronegativity values.
In order to form an ionic compound, the elements reacting together must have very different tendencies to lose or gain electrons. These are two inter-related ways of recognizing this: the position of the elements in the Periodic Table and their electronegativity.
Electro-negativity is a measure of the ability of an atom to attract electrons. So electronegativity values can also be used to determine whether an ionic compound will result from two specific elements reacting together. It is generally recognized that a difference of 1.8 units or more on the Pauling scale will give a compound that is predominately ionic.
One element will usually be a metal on the left of the Periodic Table and the other a non-metal on the right. As well, we learned that the tendency to lose electrons and form positive ions increases down the groups on the left, whereas the tendency to gain electrons and form negative ion increase up the groups on the right.
4.1.7 State the formula of common polyatomic ions formed by metals in periods 2 and 3
Nitrate NO3 charge 1-
Hydroxide OH charge 1-
Hydrogen Carbonate HCO3 charge 1-
Carbonate CO3 charge 1-
Sulfate SO4 2-
Phosphate PO4 3-
Ammonium NH4 1+
4.1.8 Describe the lattice structure of ionic compounds.
The forces of electrostatic attraction between ions in a compound cause them to surround themselves with ions of opposite charge. As a result, the ionic compound takes on a predictable three-dimensional crystalline structure known as an ionic lattice.
The strength of the force between the ions is expressed in its lattice enthalpy. The higher the charges on the ions and the smaller their size, the large the lattice enthalpy and the more energetically stable the ionic compound. The term coordination number is used to express the number of ions that surround a given ion in the lattice. For example, for every 6 sodium ions there are 6 chlorine ions.
Lattice consists of a large number of ions and it can grow indefinitely. As ionic compounds do not exists as units with a fixed number of ions, their formula are simply an expression of the ratio of ions present.
This comment has been removed by the author.
ReplyDelete