Periodic Table: Classification of Elements in the Periodic Table

len Alfred Ajibola - Tue, 26th March, 2019 @ 6:15 PM

Topics in Chemistry

Le Chatelier's Principle: Changes in Concentration and Pressure explained in Dynamic Equilibrium Chemical Equilibrium: Dynamic Equilibrium in Chemistry Static and Dynamic Equilibrium explained with their Differences Chemistry Scheme of Work, SS1, First Term Chemistry Scheme of Work, SS1, Second Term Chemistry Scheme of Work, SS1, Third Term Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry

Academic Questions in Chemistry

Please check out our Test Your Knowledge page to see all Questions and Answers

Which of the following statement is false concerning hydrocarbons?

  • A. Hydrocarbons can be aromatic

  • B. Hydrocarbons are made up of carbon and hydrogen only

  • C. Alkynes are aliphatic hydrocarbons

  • D. Alkenes have a carbon-carbon double bond in their structure

  • E. Benzene ring has a carbon-carbon triple bond in its structure

  • F. Hydrocarbons are the main constituents of petroleum and natural gas

The ability of carbon to form long chain of itself is called _____.

  • A. Carbon chain reaction

  • B. Catenation

  • C. Carbontion

  • D. Carbontion

  • E. Organic chemistry

  • F. Carbon moleculation

Calculate the relative molecular mass of methane. (Carbon = 12.001, H = 1.00794).

  • A. 13.00894 amu

  • B. 11.00206 amu

  • C. 12.00794 amu

  • D. 14.001 amu

  • E. 15.001 amu

  • F. 16.033 amu

Which of he following is not a fact concerning gold?

  • A. 24 karat gold is the purest gold element

  • B. It is the 50th rarest metal amongst all elements found beneath the earth crust

  • C. It is the most malleable and ductile pure metal ever known

  • D. It is the only metal with a golden color

  • E. Gold is non toxic and can be eaten with food

  • F. It's present inside the earth crust in all seven continents

Which of the following is not an example of a chemical change?

  • A. The burning of wood
  • B. The melting of candle wax
  • C. The decomposition of food
  • D. The rotting of leaves
  • E. The lightening of a match stick
  • F. None of the above

Which of the following is not a fraction of crude oil?

  • A. Gasoline
  • B. Naphtha
  • C. Benzene
  • D. Wax
  • E. Paraffin
  • F. Lubrication Oil

The Separating Funnel is a technique used in the separation of mixtures. Another name for Separating Funnel is the _____ Funnel.

  • A. Partition
  • B. Separatory
  • C. Division
  • D. Liquid
  • E. Half
  • F. Dividing

2NH4+(aq) + Ag+(aq) -> 2H4AgN

The equation above represents _____ acid.

  • A. Svante Arrhenius'

  • B. Brønsted–Lowry's

  • C. Gilbert Lewis'

  • D. Avogadro's

  • E. Sir Isaac Newton's

  • F. Albert Einstein's



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Periodic Table:

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.

  • Recall that atomic number is the number of protons in the nucleus of an atom.

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.

Please read on the Physical Properties of Metals here.

On the periodic table, atomic symbol of elements are used to represent each element. As an instance, the element sodiun is represented as Na.

Note: The atomic number of each element of the periodic table can be seen on the top left (or on top) of each atomol symbol. Also seen are the elements' atomic mass just below the atomic symbol.

Atomic mass is the sum of protons and neutrons in the nucleus of an atom.

Below is a diagram that shows the periodic table of elements:

Periodic Table - Len Academy

Please read on Acids - Physical and Chemical Properties of Acids here.


Classification of elements on the periodic table

  • Groups

The vertical columns of the periodic table are called the groups. They are present in the 'up - down' direction of the table.

The groups are 8 in numbers (numbered I, II, III, IV, V, VI, VII and VIII). They appear to be the most significant criteria in the classification of elements in the periodic table.

Most of the elements within a group have similar chemical properties and share a common name. For instance, the group VIII elements are referred to as the 'noble or rare or inert gases' while groups I, II and VII are called alkali metals, alkali earth metals and halogens respectively.

All elements in the same group have the same valence electron(s). For instance, all group I elements have one valence electron while group II elements have got two.

Valence electrons(s) is/are the number of electron(s) in the outermost shell of an atom. It is shown in the image below:
Valence Electron - Len Academy

The outermost electrons (valence electrons) determine the chemical behaviour of elements, giving rise to the basis of the periodic law.

The periodic law states that the properties of the elements are a periodic functions of their atomic numbers. To simply put it, elements with the same valence electron(s) will tend to chemically behave in a similar way.

You can read on an introduction to Organic Chemistry here.


  • Periods

The horizontal rows of the periodic table make up the periods (left - right). They also show some similar trends; for instance, all elements in period one have got one shell while elements in period two have two shells or atomic orbitals.

Note: Electrons revolve round the shell.

As we go across the period, the number of electrons increases by 1.


  • Blocks

Elements in the periodic table are also classified into blocks depending on the electrons present on the outermost shell of the of elements. For this reason, we have the following blocks of elements:

  • s-block elements
  • p-block elements
  • d-block elements
  • f-block elements

An understanding on how the electronic configurations of elements are written for their respective blocks is important. As an instance, Helium (He) is an s-block element simultaneously belonging to group VIII and period 1 of the periodic table. It's electronic configuration is written as 1s2.

You can read on Salts in Chemistry here.

Apart from the above classifications, elements in the periodic table can further be classified as:

  • Transition metals

  • Lanthanides

  • Actinides

As a student, understanding the chemical properties and trends that elements share within the groups and periods is crucial.

The chemical trend seen in the periodic table include:

  • Atomic Radius

  • Ionic Radius

  • Ionization Energy

  • Electronegativity

  • Electron Affinity

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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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Amazing facts in Chemistry

The only letters that failed to appear on the periodic table are letters:

J     &     Q

Gold and copper are the only two non-silvery colored metals.

Please read some interesting facts about gold here

Copper is the only metal that is naturally antibacterial. This is why you would see some children utilize 'copper' water bottles in schools

Water actually 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.

Please read on modification of Dalton's atomic theory here.

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


A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.

Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.

The large molecules (above) have no specific chemical formula throughout their volume.

Please read more on Carbohydrates and Sugars here

Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the Modifications of Dalton's Atomic Theory.

Please read on Dalton's Atomic Theory and its Modifications here.

Calculate the Relative Molecular Mass of Methane (CH4). (Carbon=12.001 and H=1.00794)

  • Molecular Mass = Atomic mass of carbon + Atomic mass of Hydrogen
  • Methane is composed of one atom of Carbon and 4 atoms of Hydrogen.
  • 12.001 + (1.00794 x 4)

Molecular Mass of Methane = 16.033 amu

Please read more on molecular mass here

Calculate the Relative Molecular Mass of Water (H2O). (Oxygen=15.9994 and Hydrogen=1.00794)

  • Molecular Mass = Atomic mass of Hydrogen + Atomic mass of Oxygen
  • Water contains 2 atoms of Hydrogen and 1 atom of oxygen.
  • (1.00794 x 2) + 15.9994

Molecular Mass of Water = 18.015 Da

Please read on Emperical Formula and its Calculations here

Gold ; Len Academy

Below are some facts about gold

  • It is the only metal that has a gold (golden) color.

  • Gold is present inside the earth crust in all the seven continents.

  • Pure gold is soft and very stretchable (It can even be stretched into threads).

  • The Latin name of Gold is aurum which means 'shining dawn'. For this reason, its chemical symbol is 'Au'.

  • Gold is a very good conductor of electricity. This is why it’s sometimes used in making USB and audio cables.

  • Gold is non toxic and can be eaten with food. It is sometimes added to desserts in some expensive restaurants.

  • The term Gold originated from an ancient English word 'geolu' which means yellow.

  • 24karat gold is the purest gold element.

Please read more interesting facts about gold here

An acid is a substance that produces Hydrogen ions (H+) when dissolved in water (or when in the form of an aqueous solution).

Svante Arrhenius definition of Acid


An acid is a substance that donates a proton in a chemical reaction.

Brønsted Thomas Martin Lowry definition of Acid


An acid is a substance that accept an electron pair in a chemical reaction.

Gilbert Newton Lewis definition of Acid


Finally, Acids can also be also defined as substances that gives out hydronium ion (H3O+) when dissolved in water.


In summary, all acids will always contain the positive H+ (cation) and an anionic group in their formula. For instance, the acid HCl (Hydrogen Chloride) contains H+ as cation and Cl- as its anion.

Please read the explanations of the above definitions of acid here