1.3 Chemical Reactions: Covalent Bonding
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Atoms can react with each other to form compounds. When atoms react, they form chemical bonds. Making bonds involves giving, taking or sharing electrons. There are two main types of bonding that are needed for the exam; they are ionic bonding and covalent bonding.
Covalent Bonding
Covalent bonds are where atoms share electrons with each other. Compounds from non-metals are known as molecules. Atoms share electrons with each other so that they completely fill their outer shells with electrons. Compounds with covalent bonds have no free electrons and no ions meaning that they cannot conduct electricity.
An example of a covalent bond is water (H2O). Oxygen shares two of its electrons; one with each hydrogen atoms. Each hydrogen atom shares one electron with oxygen. Hydrogen now has access to two electrons and thus has a full outer shell (its first shell has 2 electrons in it). Oxygen has access to two more electrons, making a total of 10 electrons meaning that its outer shell is full (oxygen will have 2 electrons in its first shell and 8 electrons in its second shell).
Covalent bonds are where atoms share electrons with each other. Compounds from non-metals are known as molecules. Atoms share electrons with each other so that they completely fill their outer shells with electrons. Compounds with covalent bonds have no free electrons and no ions meaning that they cannot conduct electricity.
An example of a covalent bond is water (H2O). Oxygen shares two of its electrons; one with each hydrogen atoms. Each hydrogen atom shares one electron with oxygen. Hydrogen now has access to two electrons and thus has a full outer shell (its first shell has 2 electrons in it). Oxygen has access to two more electrons, making a total of 10 electrons meaning that its outer shell is full (oxygen will have 2 electrons in its first shell and 8 electrons in its second shell).
Covalent bonds in water.
A compound will have different properties to the properties of each of the elements.
Equations
When a chemical reaction occurs, no atoms are lost or made during the chemical reaction. You have the same number of each element after the reaction as before the reaction took place. This means that the mass of all the atoms before the reaction is the same as the mass of all the atoms after the reaction. We can write chemical reactions in words or in formulas. Let’s use water as an example:
When a chemical reaction occurs, no atoms are lost or made during the chemical reaction. You have the same number of each element after the reaction as before the reaction took place. This means that the mass of all the atoms before the reaction is the same as the mass of all the atoms after the reaction. We can write chemical reactions in words or in formulas. Let’s use water as an example:
Word: Hydrogen + Oxygen = Water
Balanced symbol: 2H + O = H2O
Balanced symbol: 2H + O = H2O
When writing out the symbol equation, one needs to make sure that it is balanced (meaning that there are the same number of each element before and after the reaction; same number of elements on each side of the equal sign). The easiest way to make sure that an equation is balanced is to find an element that is currently unbalanced and to start adding numbers in front of the entities so that it balances.
Suppose that we have iron (III) oxide and we want to extract by reduction with carbon. After the reduction reaction has taken place, we will have iron and carbon dioxide.
Suppose that we have iron (III) oxide and we want to extract by reduction with carbon. After the reduction reaction has taken place, we will have iron and carbon dioxide.
Iron (III) Oxide + Carbon -> Iron + Carbon Dioxide
Fe2O3 + C -> Fe + CO2
Fe2O3 + C -> Fe + CO2
The element that we are going to check is Oxygen. On the left-hand side, there are 3 atoms of oxygen. But on the right-hand side there are only two atoms which are oxygen. Therefore, the equation is not balanced. We can now add a number to one of the entities and see what this gives us. Let’s add a 2 in front of the iron (III) oxide (Fe2O3).
2 Fe2O3 + C -> Fe + CO2
By having two iron oxide compounds, we will get 3 carbon dioxides as a result. However, if we check the number of carbon atoms, we will see that there is only one on the left-hand side and three on the right-hand side. This can be overcome by placing the number 3 in front of carbon.
2Fe2O3 + 3 C -> Fe + 3 CO2
We now have the same number of carbon and oxygen atoms on each side. We need to check the final element type which is iron. Currently there are 4 iron atoms on the left and 1 on the right. We can solve this by placing a 4 in front of iron on the right side.
2 Fe2O3 + 3 C -> 4 Fe + 3 CO2
A good strategy is to do a final check of all the different elements. There are 4 iron atoms, 6 oxygen atoms and 3 carbon atoms.