The modern periodic table is not only constructed on the increasing atomic number but also using the work of Newlands, elements are divided into groups of similar physical properties and reactivities. The groups are the vertical columns of the periodic table.
When referring to reactivity of an element this is its relative ease of creating a compound when reacting with another element to form a compound, this often relates to how easy that element will lose or gain electrons. Scientists constructing groups of the periodic table were able to study how elements reacted with other elements and spot common similarities and differences. There are 18 groups in the periodic table spanning from left to right.
An example of this is the reaction of Group 1 metals with water. All group 1 metals will react with water to produce a hydroxide solution and hydrogen gas but progressing down the group 1 the reaction gets more violent as the outer electron (valence electron) is lost a lot more easily. this can be seen in the observations of the reaction. Lithium will react with water giving a small fizz and bubbling but when reacting caesium with water it reacts violently exploding and creating a lot of heat. It is these similarities in reactivity that have allowed scientists to group chemicals together into groups based on their chemical and physical similarities. This is in contrast the elements in Group 18 (Noble Gases) are relatively unreactive and are all gases. All the gases in group 18 are similar in properties being heavy, unreactive and having full outer shells. The unreactive nature of the group 18 elements is due to their inability to gain or lose electrons due to their full outer shell.
Through the work of Newlands and Mendeleev, the modern periodic table has very interesting patterns. Not just on reactivity and chemical reactions but also the structure of the electron shells, the presence of metals and non-metals and also their appearances. Before most modern techniques elements were often grouped together by their appearances only. The first example of this was the grouping of metals and non metals, the two largest categories of the periodic table. Most metals in their elemental state are shiny, silver and strong compared to non metals that are brittle, coloured and powdery substances. For example, the Group 18 gases whilst being unreactive and colourless all exhibit the property of being able to conduct an electric current which produces different colours based on this appearance they can be classified into the same group.
Atomic number is the number of protons in the nucleus
John Newlands was a British scientist who divided 56 elements into groups
Elements are atoms with the same number of protons in the nucleus
Physical properties are characteristics of an element or compound that are physical such as melting points and boiling points
Groups are the columns of the periodic table with elements that are grouped together with similar properties
A compound is when two or more elements are joined together by a bond which forms when they share electrons or move them between each other
A hydroxide is a compound that contains an oxygen and. hydrogen atom bonded together an ion to form the OH- ion which is known as the hydroxide ion
Noble gases are very unreactive non metal elements found in group 18 of the periodic table. They do not react with other elements easily and are all gases.
Unreactive describes an element or atom that will not change because of another as they are quite stable
A full outer shell is known as the noble gas configuration where the outer shell of an atom is energetically stable and contains 8 outer electrons
Dmitri Mendeleev was a Russian scientist who in 1869 proposed the first structure of the periodic table
Brittle is used to describe a physical property where layers of atoms when moved across each other will break apart. Commonly in ionic lattices as the ions repel each other