Alfred Ajibola
- 21st November, 2025 @ 10:42 AM
Topics in Chemistry
Chemistry Scheme of Work, SS1 Third Term Chemical Industries: Petrochemicals, Biodegradable, Non-biodegradable Wastes and Pollutants Chemical Industries: Types, Advantages, Disadvantages and Factors affecting Chemical Industries Hydrocarbons: Fractional Distillation of Crude oil and Uses of its Fractions Hydrocarbons: Sources, Classification and Test for Saturated and Unsaturated Hydrocarbons Trioxocarbonates: Preparation, Physical and Chemical Properties, Tests and Uses of Trioxocarbonates Carbon and its Compounds: Oxides of Carbon, Carbon(IV) oxide Carbon and its Compounds: Oxides of Carbon Amorphous Allotropes of Carbon Carbon: Structure and Allotropes of Carbon Salts in Chemistry: Types, Properties, and Uses of Salts Salts in Chemistry, their Classifications, Solubility, Preparations and Colors pH Indicators, Types of Indicators and Importance of pH and pOH Relative Acidity and Alkalinity (pH Scale), and Calculations on pH Bases and Alkalis: Definitions, Classification, Physical and Chemical Properties Bases: Preparation of Bases and Alkalis, Test and Uses Physical and Chemical Properties of Acids, Preparation, Test and Uses of Acids. Acid: Definition, Basicity, and Types of Acid Families of elements in the periodic table Periodic table and Classification of ElementsAcademic Questions in Chemistry
With regards to redox reactions, which of the following statement is wrong?
A. Redox reaction are examples of chemical change
B. Reduction is the gain of electron
C. Substances that donates election during chemical reaction are termed reductants
D. Oxidizing agents are always reduced in chemical reactions
E. Oxidation occurs at the cathode in electrolysis
F. Hydrogen is a reducing agent
In chemistry, physical change is associated only with the rearrangement of molecules while the internal composition of the substance remains the same.
A. True
B. False
_____ electron(s) is a term that describes the number of electron(s) in the outermost shell of an atom.
A. Outer
B. Excess
C. Valence
D. Positive
E. Negative
F. Last
_____ is the negative electrode in electrolysis.
A. Anode
B. Anion
C. Cathode
D. Cation
E. Ion
F. Electrolyte
The above diagram shows the _____ type of bond.
A. Covalent
B. Polar covalent
C. Coordinate covalent
D. Metallic
E. Van dear walls
F. Ionic
Metals are referred to as _____ in their impure state.
A. Diluted
B. Consecrated
C. Coloured
D. Ores
E. Stained
F. Strained
Metals generally have the quality to shine, glow, sparkle, glitter, reflect light and be polished. This characteristic of metals is termed _____.
A. State
B. Ductility
C. Luster
D. Malleability
E. Hardness
F. Inflorescence
The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.
A. Mole
B. Volume
C. Weight
D. Number of moles
E. Mass
F. Amount of substance
The periodic table is the table which shows the arrangement of elements in the order of
increasing atomic number.
The historical development of the periodic table began with the classification of elements by Antoine Lavoisier in 1789, whose classification was essentially into gases, metals, non-metals and earths. Other scientists like Johann Wolfgang Döbereiner, Newland and Lother Meyer also attempted to classify elements based on their properties.
In 1869, a Russian scientist, Dmitri Mendeleev prepared the first periodic table where he arranged elements based on their atomic masses. Mendeleev's development of the periodic table was based on the periodic law. His periodic law is stated below:
Dmitri Mendeleev periodic law stated that the properties of the elements varied periodically with their relative atomic masses.
Please read on atomic and molecular mass here.
Mendeleev arranged the elements in increasing order of relative atomic mass. With this, elements having
similar properties kept recurring at regular intervals or periods, forming families of related elements.
With the discovery of the electronic structure of the atoms, it became clear that elements do vary regularly (not with their relative atomic mass), but with their atomic number. Hence, in the modern periodic table, classification is based on atomic number, rather than their relative atomic masses. This gave rise to the modern periodic law which is stated below:
The modern periodic law states that the properties of elements are a periodic function of their atomic number.
Please read on elements and their characteristics here.
The modern form of the periodic table is divided into eight vertical columns termed "Groups" and seven horizontal rows known as "Periods". These are explained below:
The vertical columns of elements or groups are numbered from I to VIII (or 0). Elements in the same group have the same number of electrons in the valence shell (or outermost shell).
With regards to hydrogen, it can be placed in
group I or VII since it can donate its one electron like the group I elements, or accept an electron like group VII elements. Regardless, hydrogen is conveniently placed in group I simply because it has only one valence electron.
In group VIII, also termed as group 0, Helium has two electrons while the other elements have got eight valence electrons.
Apart from the eight groups, there are also the transition group of elements (termed the transition metals). These lay between group II and III elements in the periodic table. They are shown in the image below:
You can read on the mole and Avogadro's number here.
The horizontal rows of elements or periods are numbered from 1 to 7. Elements in the same
period have the same number of electron shells.
It is noteworthy to state that period 6 and 7 contain a special class of elements called the Lanthanides and Actinides series. These are known as the inner transition metals. They are typically placed at the bottom of the periodic table to keep it from becoming too wide, and are also known as inner transition elements or f-block elements.
You can read on Dalton's Atomic theory and it's modifications here.
The elements in the periodic table may be divided into blocks. These blocks of elements is determined according to the orbital in which their valence electrons are present; and thus responsible for the positions of these elements.
The blocks of elements are put into the following:
The s-block elements which have s electrons in the outermost energy level. S-block elements are found in Groups 1 and 2 of the periodic table. The group I elements are termed the alkali metals (with the exception of hydrogen), while the group II are called alkaline earth metals. They are called s-block elements because their last electron enters the s-orbital.
The p-block elements has both s and p-electrons. This block includes a wide variety of elements like non-metals, metalloids, noble gases and even metals like aluminum. Examples of p-block metals include nitrogen, oxygen, fluorine, aluminum, and the noble gases. They are characterized by the general outer electron configuration of ns2 np1-6.
The d-block transition elements contain the inner d-electrons in addition to its s and p-electrons. Their electronic configuration ensures that the last electron enters the d-orbitals of the penultimate shell. Transition metals include chromium, manganese, iron, copper and zinc; and they are present between the s-block and p-block elements. Their properties are influenced by the presence of unpaired d-electrons, which can lead to variable oxidation states and magnetic properties.
The f-block elements include the lanthanides and actinides series. They contain the f-electrons in addition to the s, p and d electrons. F-block elements are the inner transition metals in the periodic table, characterized by the last electron entering an (n-2)f orbital. They are divided into two series, the lanthanides (4f series) and the actinides (5f series), and are typically placed separately at the bottom of the periodic table.
Please read more on the periodic table and classification of elements here.
Note: The "spdf" electronic configuration is a method for describing the arrangement of electrons in an atom's orbitals, where 's', 'p', 'd', and 'f' represent the different types of subshells. Each subshell has a maximum number of electrons it can hold: That is; s subshell can hold a maximum of 2 electrons, p can hold 6, d (10), and f (14) respectively.
You can read on the introduction to chemistry here.
The table below shows the spdf electronic configuration of the first 20 elements:
|
Atomic Number |
Elements |
Electronic Configuration |
|
1 |
H |
1s1 |
|
2 |
He |
1s2 |
|
3 |
Li |
1s2 2s1 |
|
4 |
Be |
1s2 2s2 |
|
5 |
B |
1s2 2s2 2p1 |
|
6 |
C |
1s2 2s2 2p2 |
|
7 |
N |
1s2 2s2 2p3 |
|
8 |
O |
1s2 2s2 2p4 |
|
9 |
F |
1s2 2s2 2p5 |
|
10 |
Ne |
1s2 2s2 2p6 |
|
11 |
Na |
1s2 2s2 2P6 3s1 |
|
12 |
Mg |
1s2 2s2 2P6 3s2 |
|
13 |
Al |
1s2 2s2 2P6 3s2 3p1 |
|
14 |
Si |
1s2 2s2 2P6 3s2 3p2 |
|
15 |
P |
1s2 2s2 2P6 3s2 3p3 |
|
16 |
S |
1s2 2s2 2P6 3s2 3p4 |
|
17 |
Cl |
1s2 2s2 2P6 3s2 3p5 |
|
18 |
Ar |
1s2 2s2 2P6 3s2 3p6 |
|
19 |
K |
1s2 2s2 2P6 3s2 3p6 4s1 |
|
20 |
Ca |
1s2 2s2 2P6 3s2 3p6 4s2 |
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Amazing facts in Chemistry
Plastic and Glass can decompose, but not in our lifetimes. It takes an average time of 450 years for plastics to decompose. As for the decomposition of glasses, it takes about 4,000 years
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals.
Copper is the only metal that is naturally antibacterial. For this reason, some children utilize 'copper water bottles' in schools
Water freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
Notable points in Chemistry
Below are the physical properties of metals:
They exist in solid state.
The have high densities.
They are good conductors of heat and electricity.
The have the ability to be polished, to glow, sparkle and reflect light.
They can be bent, flattened and made into sheets called foils.
They can be drawn into wires.
Iron undergoes magnetism while most metals are poorly magnetized.
They typical have high melting point.
They generally have high boiling point.
With the exception of lithium, sodium and potassium, most metals are generally hard.
They have the ability to make sound when in contact with other objects or metals.
Please read details on the physical properties of metals here
John Dalton is an English chemist who brought clarity into the composition of matter and the basis for their chemical reactions.
Below are Dalton's Atomic Theory:
All matter consists of tiny indivisible particles called atoms.
Atoms of the same element are identical to each other in every aspect because they have the same shape and mass, while atoms of different elements are different in all respect.
Atoms are indestructible and can neither be created nor destroyed.
Atoms of different elements can combine with each other in simple whole number ratios to form compounds.
Atoms of the same element share similar physical and chemical properties. They can also combine in more than one ratio to form two or more compounds.
Meanwhile, understand that the above theories of John Dalton had been modified.
Please read on Dalton's atomic theory and its modifications here
The periodic table, also called periodic table of elements or Mendeleev's table, is a table that shows an organized arrangement of the 118 chemical elements according to their atomic number.
Out of the 118 elements; elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially.
The manner at which elements are arranged on this table reveals some similarities in their electronic configurations and chemical properties.
A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)
Step 1: Identify the given parameter from the question.
Fe = 69.94%, O = 30.06%.
Empirical formula = Fe?O?
Step 2: Convert the percentages to gram. (just attribute grams to the %).
Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in emperical formula.
Mole of Fe: 69.94/55.85 = 1.252mol
Mole of O: 30.06/16 = 1.879mol
Step 4: Divide both sides by the smallest mole ratio.
Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1, 1.879/1.252 = 1.5
We now have the formula = Fe1O1.5
Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.
For iron (Fe), we will have 1 x 2 = 2
For oxygen (O), we will have 1.5 x 2 = 3
Step 6: Write the empirical formula.
The empirical formula= Fe2O3
Iron(III)tetraoxosulphate(VI)
In chemistry, hydrocarbons can be classified as either aliphatic or aromatic. Recently, both classifications of hydrocarbon were based on their structure rather than their origin.
Aliphatic hydrocarbons are put into three main groups according to the types of bonds they possess. These are:
Alkanes
Alkenes
Alkynes
They are shown in the image below:
It's important to note the followings:
Alkanes have single bonds (only) in their structures.
Alkenes always have a carbon-carbon double bond present in their structure.
Alkynes always have a carbon-carbon triple bond present in their structure.
Aromatic hydrocarbons are classified into:
