Chemical Bonds: Ionic, Covalent and Metallic

1. What type of chemical bond forms when a substance is formed from: two non-metals ; two metals ; a metal and a non-metal.

Answer: two non-metals form a covalent bonding ; two metals form a metallic bonding ; a metal and a non-metal form an ionic bonding


2. State whether electrons are shared between atoms, or transferred from one atom to another, in these types of chemical bond: ionic bonding ; metallic bonding ; covalent bonding.

Answer: in the ionic bonding electrons are transferred ; in the ionic and metallic bonding electrons are shared


3. Name the type of compound consisting of a lattice structure of oppositely charged ions.

Answer: An ionic compound


4. Name the type of bonding that occurs between nitrogen and hydrogen atoms in molecules of ammonia (NH3 ).

Answer: Covalent bonding


5. Draw a dot and cross diagram for each of the following molecules: hydrogen chloride (HCl) ; water (H2O) ; ammonia (NH3)

Answer:  


6. Draw a simple two-dimensional diagram to represent metallic bonding. Label your diagram.

Answer:  


7. Sodium, chlorine and hydrogen are three very reactive elements. These elements can react to form different types of compounds with different structures.

a) Give the type of bonding present in sodium.

Answer: metallic bonding


b) Give the type of bonding present in Cl2 molecules.

Answer: covalent bonding


c) Sodium hydride (NaH) forms when sodium reacts with hydrogen. Hydrogen chloride (HCl) forms when chlorine reacts with hydrogen. Compare the bonding and structure of NaH to that of HCl. Explain your answer in terms of particles and electrons.

Answer: NaH is formed from a metal reacting with a non-metal. Electrons are transferred from the sodium atoms to the hydrogen atoms. The particles are ions, Na+ and H- , and the bonding is ionic with a giant lattice structure. HCl is formed from two non-metallic elements reacting together. Electrons are shared between the atoms. The particles are molecules and the bonding is covalent.


8. The ionic compound magnesium fluoride forms when magnesium metal reacts with the non-metal fluorine. Magnesium is in Group 2 and fluorine is in Group 7 of the periodic table.

a) Determine the formula of magnesium fluoride.

Answer: Mg forms 2+ ions  and  F forms 1− ions. Formula is MgF2 .


b) Both magnesium and fluorine atoms form ions with the electronic structure of a noble gas. Draw the electronic structure of both ions and give the name of the noble gas that has the same electronic structure.

Answer: Both ions have the same electronic structure as neon atoms.  


c) The figure below shows the structure of magnesium fluoride represented using the ball and stick model. Give one limitation of representing this structure using this model.


Answer: the sticks in the image may be confused with covalent bonds but there are no covalent bonds present ; the model suggests the ions are far apart, and they are not.


d) Describe the changes that take place in the magnesium and fluorine atoms when they react together to form ions.

Answer: Each magnesium atom loses its two outer-shell electrons to form magnesium ions with a 2+ charge (Mg2+). Each fluorine atom gains one electron to get a full outer shell, forming a fluoride ion with a 1- charge (F). The oppositely charged ions attract each other and form a giant lattice structure.


9. Silicon reacts with hydrogen to form a covalent compound made up of small molecules. Silicon reacts with oxygen to form a covalent compound with a giant structure.

a) Write the balanced symbol equation for the reaction between silicon and hydrogen gas to form silane (SiH4 ). You do not need to include state symbols.

Answer: Si + 2H2  →  SiH4


b) Copy and complete the dot and cross diagram in the figure below to show the covalent bonding in a molecule of (SiH4 ).


Answer:  


c) The figure below shows the structure of silica (SiO2 ). Suggest what each small sphere and each line represents in this figure.


Answer: Each circle represents an atom and each line represents a pair of electrons.


d) The figure below shows two representations of a giant structure. One is a ball and stick structure and the other is a three-dimensional structure. Give one advantage of a three-dimensional space filling representation over a ball and stick diagram.


Answer: 3D space-filling models give a better representation of how close the atoms are ; 3D space-filling models show how the atoms merge together when they bond


e) Pyrosilicic acid is a covalently bonded compound containing hydrogen, silicon and oxygen. The figure below shows the stick diagram for a molecule of pyrosilicic acid. Give the molecular formula for pyrosilicic acid.


Answer: H6Si2O7


10. The figure below is a representation of the bonding in the element sodium.


a) Describe fully the type of bonding represented by this figure.

Answer: This figure represents metallic bonding. There is a giant lattice of metal atoms. The outer-shell electron from each atom becomes delocalised, which means they can move throughout the whole structure. There is a strong attraction between the delocalised electrons and the positive nuclei of the metal atoms (this is the metallic bond).


b) Sodium can be made by heating sodium carbonate (Na2CO3 ) with carbon. The products of the reaction are sodium and carbon monoxide (CO). Write the balanced symbol equation for this reaction.

Answer: Na2CO3 + 2C  →  2Na + 3CO