STRUCTURES AND BONDS

STRUCTURES AND BONDS

By the end of this chapter, you should be able to:

• Understand that atoms are the building blocks from which all matter is made
• Understand the terms ‘element’, ‘atom’, molecule’ and ‘compound’, and appreciate how they are related. 
• Understand how atoms of different element differ in their subatomic structure
• Appreciate that atoms are made up of subatomic particles and know the properties of the particles.
• Understand the terms relative atomic mass, proton number, nucleon number and isotopes
• Understand the appreciate that the atoms of elements join together to form compounds
• Understand the processes involved in the formation of ionic, covalent and metallic bonds
• Recognize the different in the physical properties of ionic and covalent compounds and relate them to their bonding.

Keywords

• Atom
• Molecule
• Compound
• Protons
• Neutrons
• Electrons
• Proton number
• Mass number
• Nucleon
• Isotopes
• Bond
• Covalent bond
• Ionic bond

Competency: you will appreciate how atoms are composed of fundamental particles and how molecules and compounds are composed of atoms.

Introduction

If you look around your class, you will see different materials or substances. Are the different materials you see the same? Probably you will find out that they are different colours, texture, states and hardness. The different substances are formed when atoms of the same or different elements combine. This can occur between atoms of the same different kind. When atoms of the same elements combine, we get molecules of the elements. But when atoms different elements combine, compounds are formed.

But why do the elements combine? The elements which are able to combine lack the electronic stability which can be attained when they combine. The properties of Substances are dependent on the nature of bonds present between their atoms. In this chapter you will learn how atoms of same or different elements combine and what they form. You will also compare the properties of the substances formed through different types of bonding.

1. Atoms are building blocks of matter

Have you thought about why different pure substances look different? The reason is that they are made up of different building blocks. The building blocks that make up matter are called atoms.

Atoms are the smallest, electrically neutral, indivisible particles of matter that can take part in a chemical reaction.

One of the early scientists called Dalton in this theory stated among others that atoms of the same element were exactly alike and different from atoms of other elements.

What are atoms made of? It is now known that atoms are made up of subatomic particles. The different in the particles may cause atoms of the same element to be different in some aspects. Activity 2.1 below, explores discoveries by different scientists about the structure of atoms. How do the theories help in understanding the structure of atoms?

Activity 2.1 exploring the discoveries related to atomic structure

What you need

Internet or any library books

What to do

In your groups, research for information about the discoveries related to the structure of atoms by the following scientists

1. Joseph Thomson
2. Dalton
3. Ernest Rutherford

Discussion

1. Imagine you are any one of the scientists. Prepare and present an oral report about your findings about the structure of atoms.
2. Discuss the similarities about atomic structure in the results of the work of each of the scientists in (1) above.
3. Of what importance are the different discoveries in understanding atomic structure?

Atoms contain sub atomic particles

There are three types of subatomic particles inside an atom. These are protons, neutrons and electrons. The protons and neutrons are found in the central part of the atom called the nucleus. The nucleus is incredibly small and dense. Figure 2.1 shows an atom showing the location of subatomic particles and electrons.

Figure 2.1 Basic structure of an atom 1

The tiny electrons move around this nucleus in areas or orbits called energy levels (shells).

Activity 2.2 Modeling the basic structure of an atom

What you need

• Materials from the environment
• Internet or any library resources

What to do

1. In your groups, search for information about the structure of atoms
2. Mobilize locally available materials that you will use to make a model of an atom

Discussion

1. Design a model showing the basic structure of an atom of Nitrogen showing the location of different particles.
2. Display your model in the class for comparison with those of other groups
3. How can you improve your model to represent atomic structure better?
4. What can you conclude from the activity?
5. elements molecules and compounds

you now know that the building blocks of matter are atoms. Look at figure 2.2 below showing pure magnesium ribbon and red phosphorus. Why do they look different?

Figure 2.2 A: Magnesium ribbon 1                     Figure 2.2 B: Red phosphorus 1

The two substances look different because they are made up of different kinds of atoms. The different substances containing different kinds of particles in a pure substance are called elements. There are over 90 naturally occurring elements and you can name the common ones using activity 2.3 below.

Activity 2.3 Naming common elements in periodic table

What you need

• periodic table
• internet or library resources

What to do

In your groups, use the Periodic table, internet or any other book to find information about the common elements and their symbols

Discussion

1. draw table showing the first 20 elements and their symbols
2. share the contents of your table with those of other members of the class
3. identify the physical states of the elements under normal conditions.

Molecules

Do you recall what you learnt in senior one about molecules? When some atoms combine with one another, they form products called molecules. Molecules are small groups of atoms chemically combined. Molecules can be made up of the same or different elements. In the next activity, you will find out more about the structure of molecules.

Activity 2.4 Representing the structure of molecules using models

What you need

• suitable materials from the environment
• internet or textbooks

What to do

1. in your groups, read about the structure of molecules
2. select materials in your environment that you will use to represent molecules

Discussion

1. Write the formulae of different molecules with:

1. Identical atoms
2. Different atoms

2. Model the structures of the molecules you have written in (1) above
3. Compare your model with those of your neighbor group
4. With help of your teacher, discuss as a class on how you can represent the molecules better.

Compounds

You have learnt that most materials we use in everyday life are compounds. Figure 2.3 shows a woman fetching water in lake Albert in western Uganda. Water is example of a compound. It is made up of hydrogen and oxygen atoms combined chemically.

Figure 2.3: Woman fetching water. Water is a compound 1

Substances which are made up of two or more different elements are called compounds.

Compounds are pure substances formed when two or more elements of different kinds chemically combine together.

Can you identify any other examples of compounds? Activity 2.5 will help you to understand the different compounds.

Activity 2.5 Modelling the structure of compounds

What you need

• Any suitable materials from the environment
• Internet or any library resources

What to do

1. In your groups, search for information about common compounds and their formation
2. Think of how you can represent the information of compounds using materials in your environment

Discussion

1. Name and write formulae of 4 common simple compounds
2. Write a word equation to show how the compound is formed from its elements
3. Compare your list of compounds with the rest of the members in the group
4. Using materials from the environment, model the structures of the compounds you have named
5. Display your models in the class to compare with the rest of the members
6. With the help of your teacher, discuss how you can improve the models to represent the compounds.
7. Elements differ in their subatomic structure

In senior two, we learnt that elements contain sub-atomic particles. Can you recall the subatomic particles that form atoms? The subatomic particles include protons, neutrons and electrons. Figure 2.4 shows a model diagram of one atom of carbon indicating the atom of carbon indicating the location of subatomic particles. As already learnt, the sub atomic particles differ in charge and mass.

Figure 2.4: Structure of the carbon atom showing the particles 1

Different atoms contain a different number of sub-atomic particles. In the next activity you will model different atoms and show their subatomic particles.

Activity 2.6 Modelling atoms with different subatomic particles

What you need

Internet or library resources

Materials from the environment

What to do

1. In your groups, use the internet or textbooks to gather information about the subatomic particles in atoms
2. Select materials to use in the modelling of different atoms

Discussion

1. In your groups, use the materials in your environment to model 4 simple atoms showing the different subatomic particles
2. Display your models in the class and compare with those of other groups
3. Explain how you can improve the models to represent the atoms better
4. sub-atomic particles in atoms differ in their properties

The sub-atomic particles in atoms differ in their properties particularly the mass and charge. Figure 2.6 shows a model of a nitrogen atom showing the different charges on the subatomic particles.

Figure 2.6: Model of a nitrogen atom showing the charges on particles 1

What are the properties of the particles? In the next activity you will show the difference in properties between the three types of sub-atomic particles.

Activity 2.8 identifying properties of sub-atomic particles

What you need

Internet or library resources

What to do

Search for information about properties of subatomic particles

Discussion

1. Identify the properties of the sub-atomic particles in an atom
2. How do these properties affect the mass number of the atom?
3. How do the properties affect the overall charge of the atom?
4. How do the properties identify affect reactivity of the elements?
5. Atomic number, Nucleon number, Isotopes and Relative atomic mass

You now know that elements are arranged in the periodic table according to their atomic numbers. Do you recall the meaning of atomic number? The atomic number Z of an element is the number of protons the atom of an element. Thus, different atoms have different atomic numbers.

Figure 2.7 Representing atomic number and mass number for helium1

The mass number (A) is the number of protons and neutrons in the atom of an element. Since the protons and neutrons reside in the nucleus of an atom, the mass number can also be called the nucleon number. In activity 2.9, you will use the periodic table to write the numbers and mas numbers of different elements.

Activity 2.9 Exploring atomic numbers and mass numbers of different of different elements

What you need

Copy of periodic table, internet or books 

What to do

1. In your groups, use the periodic table to explore the common elements, their atomic numbers and mass numbers.
2. In groups, use the internet or textbooks to search for more information about atomic numbers and mass numbers.

Discussion

1. Draw a table, showing the first 20 elements, their atomic numbers and mass numbers.
2. Explain why it is important to arrange elements, their atomic numbers and mass numbers.
3. What can you conclude from this activity?

Relationship between mass number and atomic number

Is there a relationship between a mass number and atomic number? You have earnt that the number of protons in an atom is equal to the number in electrons. You are also aware that the number is the sum of protons and electrons. Mathematically?

Protons + neutrons=mass number

 We can use the information to solve the problems involving the particles in an atom.

Worked example 2.1 calculating mass number

What is the mass number of atom which contains 14neutrons and 13 protons in its nucleus?

1. Looking for: You are asked to the mass number.
2. Given:           You are given the proton number and neutron number.
3. Relationships: use the relationship: proton + neutron= mass number
4. Solution:        Substitute and solve: neutrons=14 + 13=27

                         The mass number is 27.

Exercise 2.1

What is the mass number of an atom which contains 18 neutrons and 17 protons in its nucleus?

Worked example 2.2 Calculating the number of neutrons

What is the number of neutrons in an atom mass number is 31 and the number of protons is 15?

1. Looking for: you are asked to find the number of neutrons.
2. Given: you are given the proton number and mass number.
3. Relationships: use the relationship: protons + neutrons= mass number.
4. Solution: substitute and solve: neutrons = 19+ -=39

                               The neutron number is 20.

Exercise 2.2

What is the neutron number of an atom which contains 56 protons and has mass number 116?

Isotopes

Dalton in this theory stated that all elements are identical. Do you agree with this assertion? It is possible to find atoms of the same element with the same atomic number but different mass numbers. One examples of an element that has isotopes is carbon. Carbon has two known isotopes. One with a mass number of 12 while the other has a mass of 14. The two carbon atoms differ in the number of neutrons in their nuclei. One other element that has isotopes is hydrogen. Figure 2.8 below shows models of the isotopes of hydrogen.

Figure 2.8: Isotopes of hydrogen 1

What difference can you see between the isotopes of hydrogen?

Isotopes are atoms of the same element with the same atomic number but different mass number.

In activity 2.10, you will explore the different elements which have isotopes.

Activity 2.10 identifying isotopes

What you need

Internet or library resources

What to do

In your groups, search for information about isotopes

Discussion

1. Identify 6 elements which contain isotopes and write their nuclear composition
2. Share your list with the rest of the class in a plenary
3. Which are common to all groups and which are different?
4. What physical differences are likely to be found in the different elements

Relative atomic mass

Figure 2.9 below shows a balance used to weigh different merchandise in our shops. To weigh for example sugar, you have to place a standard stone and relate it with an equal mass of sugar.

Figure 2.9: Weighing balance 1

Similarly, because the actual masses of atoms are very small, we measure them against a standard mass. The mass of carbon-12 atom, 12C6 is used as the standard atom against which the masses of other atoms are compared.

The relative atomic mass of an element is the average mass of its atoms, compared to 1/12^th the mass of a carbon-12 atom Sloper.

Since some elements have isotopes, the relative atomic mass, A, of an element is calculated from the mass numbers of its isotopes and their abundance. The relative atomic mass of an element is the average contribution of the isotopes. It is given by:

RAM=Isotopes mass x percentage abundance of the isotope( ∑means sum of the elements)

Worked example 2.3 Calculating relative atomic mass

Natural chlorine consists of 75% chlorine -37 and 25% chlorine-35. What is the relative atomic mass of chlorine?

Contribution from chlorine-35=35x 75/100= 26.25

Contribution from chlorine-37=37x 25/100=9.25

Relative atomic mass= 26.25+9.25=35.5

Exercise 2.3

The table shows the mass numbers and abundances of naturally occurring copper isotopes.

1. Calculating the relative atomic mass of copper. Give your answer to 1 decimal place.
2. How does the calculated relative mass compare with the isotopic masses
   6. Atoms combine to form compounds

Why do atoms combine?

You have observed that the materials in our midst are predominantly made up of more than atom combined. Why do the atoms combine? To understand why chemical bonds form, consider the common compound known as water (H2O). It consists of two hydrogen (H) atoms and one oxygen (O) atom. As you can on the left side of the figure 2.10 below, each hydrogen atom has just one electron, which is also its only valence electron. The oxygen atom has six electrons in the outer energy level but only 2 are unpaired.

Figure 2.10: Demonstrating formation of a water molecule1

In the water molecule on the right in the Figure 2.10 above, each hydrogen atom shares a pair of electrons with the oxygen atom. By sharing electrons, each atom has electrons available to fill its outer energy level. In the water molecule, each of the hydrogen atoms has a pair of shared electrons making its outer energy level fully filled with electrons. The oxygen atom has a total of eight electrons in its outer shell, so its outer energy level is also full. A full outer energy level is the most stable possible arrangement of electrons. It explains why elements form chemical bonds with each other.

Outer electrons are responsible for bonding

You have already learnt that atoms combine to attain a fully filled outer energy level. Which electrons are involved in chemical bonding? Electrons in inner energy levels occupy a completely full energy level. In addition, they are not accessible or available to combine. Therefore, it is the outer electrons which undergo chemical bonding to be fully filled by the electrons. The outer electrons of an atom are called valency electrons. Figure 2.11 below shows the valence electrons in a carbon atom.

Figure 2.11: valence electrons in the carbon atom 1

In activity 2.11, you will represent structures of atoms and show valence electrons.

Activity 2.11 Representing electronic structures of atoms by showing valence electrons

What you need

• Materials from the environment
• Manila paper
• Assorted markers
• Internet or textbooks

What to do

• In your groups, use internet or textbooks to gather information about structures of atoms and valency electrons
• Select suitable materials from the environment for use in modeling structures of atoms

Discussion

1. Using a manila paper, draw the structures of the first 5 non-noble gas elements showing the valency electrons
2. Using the structures, you have drawn, model structures of the atoms showing the valence electrons using materials in the environment.
3. Display your models in class for sharing with your classmates
4. What does the valency electrons indicate about the reactivity of atoms?

Atoms can lose or gain electrons to form ions

You have learnt valency electrons are responsible for chemical bonding. You have also learnt that atoms combine in order to gain the stable electronic structure of noble gases. But how can this structure be attained? The noble gas structure is attained by loss or gain of electrons, ions are formed. The figures below (2.12 and 2.13) show an illustration of loss and gain of electrons by atoms. Note the noble gas structure attained in each case.

Figure 2.12: Formation of a sodium ion 1

Similarly, the formation of a fluoride ion involves gain of an electron to form a negative ion.

Figure 2.13: Formation of chloride ion. 1

Activity 2.12 Demonstrating loss and gain of electrons by atoms

What you need

• Internet
• Manila
• Assorted permanent markers
• Suitable materials from environment

What to do

1. In your groups, search the internet for information on ion formation.
2. Select suitable materials in your environment for modelling the formation of ions

Discussion

1. Draw electronic structures to show the formation of ions from the following elements

1. Magnesium
2. Oxygen
3. Aluminum
4. Fluorine

2. Model the structures you have drawn using locally available materials in the environment
3. Display your models for sharing with rest of the class
4. What are the similarities or differences in the electronic structures of the different groups?
5. What can you conclude about the formation of ions by different elements?
6.  Formation of ionic, covalent and metallic bonds

How do atoms make molecules and compounds? Typically, atoms and molecules join together in such a way that they lose their identities as elements and adopt a new identity as molecules and compounds. This process is called chemical bonding. The three common types of chemical bonds include covalent, ionic, and metallic bonds. Each type of bonding is described below.

Ionic bonding

Chemical bonding takes place between electrons in the outer energy level. You also know that bonding takes place for the atoms to be stable. Stability can be attained if atoms lose gain or share their valence electrons. Ionic bonding takes place when atoms are transferred from one atom to another.

An ionic (electrovalent) bond is formed by the transfer of electrons between atoms.

Figure 2.14 below shows loss and gain of electrons in the formation of sodium chloride.

Figure 2.14 Formation of sodium chloride 1

As show in figure 2.14, the sodium atom loses its outer electron to the chlorine atom forming a positive charge while chlorine forms a negative charge. The two oppositely charged ions attract each other and combine chemically to form sodium chloride. You can illustrate the bonding between atoms by carrying out activity 2.13

Activity 2.13 Drawing and modeling ionic compounds

What you need

• Internet or text books
• Manila
• Assorted permanent markers
• Suitable materials from environment

What to do

1. In your groups, search the internet for information on formation of ionic compounds.
2. Select suitable materials in your environment for modelling the formation of ionic compounds

Discussion

1. Draw diagrams to illustrate the formation of ionic bonds in magnesium oxide and sodium fluoride
2. For the drawings in 1, model a basic structure showing the bond formation
3. Compare your model to that of the other groups

Covalent Bonding

You have already learnt that ionic compounds are formed by the transfer electrons. One other type of bonding is covalent bonding. Unlike ionic bonding, covalent bonding involves the sharing of electrons between atoms. Contrary to ionic bonding where the atoms must be metals and non-metals, covalent bonding takes place between non-metals. One example of covalent bonding is the formation of hydrogen chloride molecule (Figure 2.15)

Figure 2.15: Formation of hydrogen chloride molecule1

You note that during covalent bond formation, the valence electrons of the two atoms are shared thus forming the hydrogen chloride molecule. you can this example to illustrate the formation of covalent bonds between other atoms by doing activity 2.14.

Activity 2.14 Drawing and modelling formation of covalent bonds

What you need

• Internet or text books
• Manila
• Assorted permanent markers
• Suitable materials from environment

What to do

1. In your groups, search the internet for information on formation of covalent bonds
2. Select suitable materials in your environment for modelling the formation of covalent bonds between atoms

Discussion

1. Draw electronic structures to show the formation of covalent bonds in molecules of:

1. Hydrogen
2. Water
3. Ammonia
4. Hydrogen chloride
5. Carbondioxide

2. Using materials from your environment model the electronic structures of molecules you have drawn in (1) above.
3. Compare your models with the rest of the groups in the class.
4. Suggest how you can improve your model to fairly represent the structures of molecules.
5. Properties of ionic and covalent compounds

You have learnt that ionic compounds are formed by transfer of electrons while covalent substances are formed by the sharing of electrons. Thus, the properties for the different compounds produced in different ways must be different. In activity 2.15, you compare the properties of compounds with the two types of bonds.

Activity 2.15 comparing melting points and solubility of covalent and ionic substances.

What you need

• Source of heat
• 4 boiling tubes
• Tongs/ wooden test tube holder
• Stop watch
• Sugar
• Cooking oil
• Distilled water
• Common salt

Caution: observe all safely precautions when using the Bunsen burner or any source of heat to avoid burns.

What to do

1. Place a small sample of common salt in a hard-boiling tube.
2. Hold the boiling tube with tongs or wooden test tube holder and heat on a flame.
3. Determine how long it takes for the salt sample to melt. Immediately stop the heating when the sample starts to melt.
4. Repeat the procedure using an equal amount of sugar.
5. Half fill another boiling tube with cooking oil. Add a spatula end full of common salt and shake gently for about 10 seconds. Record your observations.
6. Repeat step 5 using sugar and note your observations.
7. Pour about 10cm³ of distilled water into a boiling tube, add a little common salt and shake.
8. Repeat step 7 by adding an equal amount of cooking oil.

Discussion

1. Which of the samples takes a longer time to melt?
2. Which substance has a higher melting point and why?
3. Comment on the solubility of sugar and salt in cooking oil
4. Which of cooking oil and common salt dissolved in water?
5. Example how the properties of the substances investigated relate to their bonding?

Electrical conductivity is the ability of a substance to conduct electricity. Do you recall from senior 2 that metals conduct electricity? Not only metals conduct electricity. Many ionic and same covalent substances conduct electricity. Also, the physical state of the substance can affect its ability to conduct electricity. For example, sodium hydrogen carbonate (baking powder) figure 2.16 cannot conduct electricity in solid state.

Figure 2.16: Baking powder does not conduct electricity1

However, it is good conductor of electricity when dissolved in water. In the next activity, you will find out whether ionic substances conduct electricity and in what form.

Activity 2.16 Investigating conductivity and physical state of covalent and ionic substances.

What you need

• Common
• Light bulb
• Dry cells
• Stirring rod
• 3 connecting wires
• 2 beakers (100cm³)
• Distilled water (200cm³)
• Microscopic slide or watch glass
• Microscopic or hand lens

What to do

1. Pour 50cm³ of distilled water into a beaker (100cm³). add some salt and stir until it dissolves.
2. Take another beaker and add some sugar. Stir the solution until it dissolves.

3. Using the beaker containing salt water, set up a circuit as shown in fig. 2.17 below and observe the results.

                        Figure 2.17: Conducting of ionic compounds  1

4. Repeat the procedure in 3 using sugar solution. What do you observe?
5. Watch grains of sodium chloride on a watch glass. What do you observe?
6. Repeat step 5 with candle wax. Note your observations.

Discussion

1. State what you observed in steps 3 and 4.
2. Explain your observations in steps 3 and 4.
3. Comment on the shape of particles steps in 5 and 6.
4. What can you conclude about the particles in steps 5 and 6?

Metallic bonding

You are probably familiar with metals such as copper, iron, aluminum and silver. But do you know what an element a metal? One is that all metals give up electrons easily. In a metal structure, there is only one kind properties.

Aluminum copper wire cast iron utensils

Figure 2.18: Metals contain the metallic bonds1

Therefore, the electrons cannot be donated since the pushing capacity is the same. In metals, the valence electrons move freely throughout the structure (they are delocalized) forming a mobile ‘sea’ of electrons. Figure 2.19 illustrates a model of the electrons surrounding the metal cations.

Figure 2.19: Model of metallic structure showing free electrons 1

The positive ions maintain the electrons in the space between the different ions. The solid structure of atoms can be modelled to fully understand this relationship between metal cations and their electrons.

Activity 2.17 drawing and modelling the structure of metals.

What you need

• Internet or text books
• Manila
• Assorted permanent markers
• Suitable materials from environment

What to do

1. In your groups, search the internet for information on structures of metals.
2. Select suitable materials in your environment for modelling the structure of metals.

Discussion

1. Draw the structure of a metal showing the free electrons.
2. Model the structure you have drawn in (1) using materials from your environment.
3. Compare your model with those of the other groups in your class.
4. How can you improve your model to fairly represent the structure of a metal.
5. Explain how the structure you have drawn and modelled accounts for the different properties of metals.

ACTIVITY OF INTERGRATION

You have been employed as a plumber in a very busy hotel. The hotel manager has narrated to you that the biggest problem in the hotel include smell from the dumping place, blockage of toilets and dirt in the sinks.

He wants you investigate the reasons and suggest solutions to the different problems faced by the hotel. Write a report to the manager explaining the causes of the problems and solutions to solve them.

Figure 2.18: Water flowing into a sink 1

Your report should include:

• Chemical nature and composition of the different materials.
• Solutions to the problems based on the chemical nature of the materials.

CHAPTER SUMMARY

•  The basic unit of matter is the atom.
• Atoms of the same elements are identical in many respects.
• Atoms of different elements differ in their subatomic structure.
• Isotopes have the same proton number but different mass numbers.
• The relative atomic mass of an element is the average mass of its atoms, compared to 1/12^th the mass of carbon-12 atom isotope.
• Ions are formed when atoms loss or gain electrons.
• Bonding is a chemical combination of atoms of the same or different kind.
• Elements combine in order to attain a noble gas electronic structure.
• Bonding can be ionic, covalent or metallic. Substances formed by the types of bonding have differences in physical properties between them.
• Ionic bonds form between non-metals.
• Metallic bonds form between metals.
• Ionic compounds are soluble in water, have high melting and boiling points conduct in aqueous form and have crystalline structures.
• Covalent compounds are soluble in organic solvents have low melting and boiling points, have molecular structures and are poor conducts of heat and electricity.
• Metallic substances have giant structures with high melting points and conduct in solid state.

REVISION EXERCISE

1. a. Distinguish between covalent and ionic bonds.

b. Compare the properties of covalent and ionic compounds

2. Explain the following observations:

(a) metals are good conductors of electricity and heat.

(b) ionic compounds do not conduct electricity in solid state.

(c) covalent compounds are insoluble in water.

3. Copper, zinc, iron and lead are metals.

(a) Mention four similarities between the metals.

(b) Explain why the similarities exist.

4. The table below shows some elements. The letters used are not actual symbols of the elements.

1. Which two different elements are likely to combine and form a covalent bond?
2. Which pairs of elements are likely to combine and form an ionic bond?
3.  Which element is not likely to combine?
4. State any 2 physical properties of element V.
5. Elements X and Y have atomic numbers 13 and 8 respectively.

1. Write electronic configuration of X and Y.
2. State the group and period of each of the elements.
3. Write the formula of the compound that can be formed between X and Y.
4. State the type of bond that can result from combination between X and Y.