Periodic table (First 20 elements) Types of chemical bonds

Subject : Chemistry

Topic :

LAWS OF CHEMICAL COMBINATION

Class :

SS 1

Term :

1st Term / First Term

Instructional Materials :

• Lagos State Scheme of Work
• Textbooks On Social Studies
• Online Materials
• Picture Charts

Previous Knowledge :

The pupils have been taught

LAWS OF CHEMICAL COMBINATION

in their previous lesson

Behavioural Objectives :  At the end of the lesson, the pupils should be able to

• Define oxidation number and, determine the ON of sulphur in SO32-
• Define a periodic table
• List the first twenty (20) elements
• State the periodic law

Content

WEEK 8

TOPIC: CHEMICAL COMBINATION

CONTENTS:

1. Periodic table (First 20 elements)
2. Types of chemical bonds
3. IUPAC system of naming inorganic compounds.

PERIOD 1:

PERIODIC TABLE (FIRST 20 ELEMENTS)

Chemical combination: The atoms of noble gases e.g. Helium He, Neon Ne are very stable; because their outermost shells are completely filled with electrons. The tendency of the other elements is to attain this stable structure possessed by the noble gases. This is achieved during chemical combination. Thus, chemical bonding is the coming together of atoms of the same or different elements, in order to form a stable structure.

The Periodic Table

Periodic table is the arrangement of chemical elements in order of their atomic numbers. Atomic number, Z, of an element is the number of protons in one atom of that element while, Mass number, A, of an element is the sum of the protons and neutrons in it.

Many scientists have attempted to classify chemical elements based on their properties. They include Newland, Lothar Meyer, Dobereiner and Mendeleev. The modern periodic table is based on Mendeleev’s original idea in 1869. The basic assumption behind the modern periodic table known as Periodic Law whichstates that “the properties of the elements are a periodic function of their atomic number”

The modern periodic Table

The modern periodic table is divided into vertical columns of elements called Groups and horizontal rows of elements called Periods. There are seven (7) periods and eight (8) groups. The first twenty (20) elements are:

Periodic table of elements

PERIODIC TABLE (FIRST 20 ELEMENTS)

1. Hydrogen

2. Helium

3. Lithium

4. Beryllium

5. Boron

6. Carbon

7. Nitrogen

8. Oxygen

9. Fluorine

10. Neon

11. Sodium

12. Magnesium

13. Aluminum

14. Silicon

15. Phosphorus

16. Sulfur

17. Chlorine

18. Argon

19. Potassium

20. Calcium

Interactive Questions and Answers 

Questions

1. What is the first element on the periodic table?

2. What is the second element on the periodic table?

3. What is the third element on the periodic table?

4. What is the fourth element on the periodic table?

5. What is the fifth element on the periodic table?

6. What is the sixth element on the periodic table?

7. What is the seventh element on the periodic table?

8. What is the eighth element on the periodic table?

9. What is the ninth element on the periodic table?

10. What is the tenth element on the periodic table?

Answers

1. Hydrogen

2. Helium

3. Lithium

4. Beryllium

5. Boron

6. Carbon

7. Nitrogen

8. Oxygen

9. Fluorine

10. Neon

EVALUATION

1. Define a periodic table
2. List the first twenty (20) elements
3. State the periodic law
4. How many groups and periods are there in the periodic table?
5. In the periodic table, elements are arranged according to their _______

PERIODS 2 and 3:

TYPES OF CHEMICAL BONDS

The attractive force between atoms when they combine chemically is called a chemical bond. There are two main types of chemical bonds namely (i) Strong bonds (ii) Weak bonds.

(i) Strong bonds are:

(a). Electrovalent (or Ionic)

(b).Covalent

(c).Co-ordinate (or Dative)

(d). Metallic

(a) Electrovalent (Ionic) bond is defined as the electrostatic force of attraction between oppositelycharged ions.

It involves the transfer of electrons from one atom, donor atom, (usually metallic) to another atom, acceptor atom, (usually non-metallic). The electrons involved reside in the outermost shells of the atoms and are called Valence electron(s).

IONIC COMPOUNDS are crystal lattices consisting of aggregates of oppositely charged ions. Examples of such compounds are Sodium chlorides, calcium oxides, ammonium chlorides etc.

The formation of sodium chloride is illustrated below:

Na = 2, 8, 1    Cl =2, 8, 7

Na+= 2, 8    Cl– = 2, 8, 8

Na++ Cl–→ NaCl

Characteristics of Electrovalent bonds

1. They have high melting and boiling points
2. They are generally soluble in water

iii .They are good conductors of electricity when molten or in solution iv. They do not conduct electricity when solid

1. The energy needed to separate them is relatively high.

(b)Covalent bonds:This is defined as the bonds formed when two atoms donate equal numbers of electrons and share the donated electrons to attain stable octet structure. In covalent bonding, electrons are shared between atoms of the same or different elements such that each atom contributes the shared electrons so as to attain stable noble gas configuration. During the process, discrete or separate molecules are formed with covalent bonds between the atoms.

If electrons are shared between similar atoms, the donated electrons are equally shared which give rise to a non-polar covalent bonde.g. F2, H2, O2, Cl2but if the shared pair of electrons involves two different elements with difference in electronegativity, the electrons are then not equally shared, this results in the formation of polar covalent bond, e.g. the formation of HCl, H2O, HF..

Characteristics of Covalent bonds i. Low melting and boiling points.

1. Energy required for separation is low
2. Do not conduct electricity in the solid or molten state, or in solution iv. They generally have a strong, easily noticeable smell

1. They are not easily soluble in water, but are usually soluble in organic solvents

• Co-ordinate covalent or Dative bond involves sharing of electrons as in the normal covalent bonding, but the shared pair is donated by only one of the participating atoms. For instance, Ammonia and water molecules possess lone pairs and so readily enter into coordinate covalent bonding.

• Metallic bond: The electrostatic force of attraction between the positive nuclei and the sea of mobile electrons is called metallic bond. Metallic bonding, therefore, is the process whereby the positively charged nuclei of metal atoms are simultaneously attracted to the sea (orcloud) of mobile electrons. Metallic bond increase with increase in valence electrons of the metal. For example, in period 3, metallic bond increases from sodium to aluminium.

(ii)Weak bonds: These are intermolecular forces of attraction that hold atoms and covalent molecules together in gases, liquids and solids. The most common ones are: (a). Van der Waals forces (b). Hydrogen bond (c)

Dipole-Dipole (Dipolar)

(e)Van der Waals forces: They were first described by J.D. van der Waals, and are known as van der Waals forces. They are weak short-ranged attractive forces formed between covalent molecules. They are the only attractive forces between the atoms of the noble gases and non-polar covalent molecules, and are responsible for the low melting and boiling point of covalent compounds. Due to increase in van der Waals forces, there is gradation in the physical properties of the Halogens: Fluorine and chlorine are gases; bromine is a liquid; and iodine is a solid.

Van der Waal force becomes stronger as the relative atomic mass increases among the non-metals.

(f) Hydrogen bond: This is an intermolecular force which arises when hydrogen is covalently linked to highly electronegative elements like nitrogen, oxygen and fluorine.

The presence of hydrogen bonds between H2O molecules is responsible for water being a liquid at room temperature and with a high boiling point; if not, it would have been a gas, like hydrogen H2S. HF is a liquid at room temperature, while HCl is a gas.

TYPES OF CHEMICAL BONDS

Interactive Questions and Answers 

Questions

1. What is a chemical bond?

2. How are chemical bonds formed?

3. What are the different types of chemical bonds?

4. How do ionic bonds form?

5. How do covalent bonds form?

6. How do metallic bonds form?

7. What are the properties of ionic bonds?

8. What are the properties of covalent bonds?

9. What are the properties of metallic bonds?

10. Which type of bond is the strongest?

Answers

1. A chemical bond is a force that holds atoms together in a molecule.

2. Chemical bonds are formed when electrons are shared between atoms.

3. There are three types of chemical bonds: ionic, covalent, and metallic.

4. Ionic bonds form when one atom donates an electron to another atom.

5. Covalent bonds form when electrons are shared between atoms.

6. Metallic bonds form when electrons are shared between metal atoms.

7. The properties of ionic bonds include: high melting and boiling points, electrical conductivity in the molten state, and insolubility in water.

8. The properties of covalent bonds include: low melting and boiling points, poor electrical conductivity, and solubility in water.

9. The properties of metallic bonds include: high melting and boiling points, good electrical conductivity, and insolubility in water.

10. The strongest type of bond is the ionic bond.

EVALUATION

• What is a chemical bond?
• List three (3) general properties of electrovalent compounds.
• Define covalent bond and state its characteristics
• State    two    (2)    differences    between    covalent    and    electrovalent compounds.
• Explain the term Metallic bonding

PERIOD 4:

IUPAC SYSTEM OF NAMING INORGANIC COMPOUNDS

Chemical compounds are named according to the International Union of Pure and Applied Chemistry (IUPAC) system. In order to understand the basic principles behind the IUPAC system, a good knowledge of the concept of Oxidation Number (ON) is very essential.

Concept of oxidation number

An oxidation number (ON) is a positive or negative number assigned to an atom according to a set of rules. It is sometimes called Oxidation State.

Naming of inorganic compounds

• Binary compounds. Binary compounds contain two elements only. The metal is named first, followed by the name of the second element ending with –ide. If the metal is one that has variable valencies, the valency exhibited will be written in Roman numeral examples are given below:

Name of compounds

• Radicals. In naming radicals, the last element is mentioned first with its number of atoms given as mono (1), di (2), tri (3), tetra (4), penta (5), etc. The other element’s name ends with –ate.

IUPAC SYSTEM OF NAMING INORGANIC COMPOUNDS

Interactive Questions and Answers 

1. What is the IUPAC system of naming inorganic compounds?

The IUPAC system of naming inorganic compounds is a set of rules and conventions that are used to name inorganic compounds.

2. How do you determine the correct IUPAC name for an inorganic compound?

To determine the correct IUPAC name for an inorganic compound, you must first identify the functional groups present in the compound. Once you have identified the functional groups, you can then use the IUPAC rules to determine the root name of the compound. The root name will be based on the highest priority group present in the compound.

3. What are the rules for assigning priority to functional groups?

The rules for assigning priority to functional groups are as follows:

1) Groups with a higher atomic number have higher priority;

2) Groups with multiple bonds have higher priority than groups with single bonds;

3) Groups with double or triple bonds have higher priority than groups with single bonds;

4) Groups with more than one atom have higher priority than groups with only one atom.

4. What is the root name of the compound?

The root name of the compound is the base part of the IUPAC name. The root name is determined by the highest priority group present in the compound.

5. What are the prefixes and suffixes used in the IUPAC system of naming?

The prefixes and suffixes used in the IUPAC system of naming are as follows: 1) Prefixes are used to indicate the number of atoms of each element present in the compound; 2) Suffixes are used to indicate the functional groups present in the compound.

6. How are prefixes used in the IUPAC system of naming?

Prefixes are used in the IUPAC system of naming to indicate the number of atoms of each element present in the compound. The most common prefixes are mono-, di-, tri-, and tetra-.

7. How are suffixes used in the IUPAC system of naming?

Suffixes are used in the IUPAC system of naming to indicate the functional groups present in the compound. The most common suffixes are -ane, -ene, and -yne.

8. What is the suffix used to indicate a compound containing a double bond?

The suffix used to indicate a compound containing a double bond is -ene.

9. What is the suffix used to indicate a compound containing a triple bond?

The suffix used to indicate a compound containing a triple bond is -yne.

10. What are the rules for naming organic compounds?

The rules for naming organic compounds are as follows: 1) The first letter of the root name is always lowercase; 2) The second letter of the root name is always uppercase; 3) Prefixes and suffixes are always lowercase; 4) The final letter of the prefix or suffix is always lowercase; 5) The letters “i” and “j” are never used as the second letter of a root name.

EVALUATION

• Define oxidation number and, determine the ON of sulphur in SO32-
• Give the IUPAC name of the following: (i) Al(NO3)3 (ii) MnO2 (III) CuSO4 .5H2O
• What is the correct IUPAC name for NO2-?

GENERAL EVALUATION OBJECTIVE TEST:

1. 1. Which of these are found in the nucleus of an atom?(a) electrons and protons B. electrons and neutrons C. protons and neutrons D. photons and electrons E. photons and neutrons.
   2. The type of bond between two atoms of an element with atomic number 7 is? A. ionic B. covalent C. hydrogen bond D. metallic bond E. coordinate covalent bond.
   3. The ON of phosphorus, P in PH3is? A. +2 B. -3 C. -1 D. +3
   4. Give the IUPAC name of the compound NO2. A. nitrogen dioxide B. nitrogen monoxide C. nitrogen (II) oxide D. nitrogen (iv) oxide
   5. Atomic number, Z, is the number of __________ in one atom an element. A. protons B. neurons C. electrons D. atoms

ESSAY QUESTIONS

1. By means of a diagram, show the arrangement of electrons in one atom of Sodium.
2. The electronic configurations for the metal calcium, the non-metals silicon and chlorine can be represented as: Ca : 2, 8, 8, ; Si : 2, 8, 4 ; and Cl : 2, 8, 7.
3. Explain, in terms of electrons, the formation of calcium chloride and silicon chloride.
4. Give two (2) differences in physical properties you would expect between calcium chloride and silicon chloride.
5. Compare the characteristics of ionic with those covalent compounds.

Use this fig. to answer questions 4 and 5.

    I    II    III    IV    V    VI    VII    VIII

1. Which of the following pairs of letters denotes elements containing the same number of electrons in their outermost shell?
2. What letter presents an element that participates in covalent rather than ionic bonding?

WEEKEND ASSIGNMENT:

New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio;

READING ASSIGNMENT:

Read about States of matter, its kinetic theory and application.