How is the Periodic Table grouped??
The Periodic Table like any other table is grouped into rows and columns. The rows are called periods and the columns are called groups. When we travel through the periodic table row-wise we see an increase in atomic number, and usually in mass too. However, the periodic grouping is not that useful. It only tells us the atomic number of an element and not much else.
However, the beauty of the modern periodic table lies in its groups. Each group has different properties. Each element of the group has similar properties on a fundamental level. Furthermore, for each group, the valency of the element remains the same.
There are 7 periods on the periodic table and there are 18 different groups in the table. These groups help divide elements into 10 distinct properties.
Alkali Metals
The Alkali Metals are the leftmost group in the periodic table, named group 1(IA). These metals have a valency of positive 1 which makes them highly reactive. These include metals like Lithium(Li),Sodium(Na), Potassium(K). These are called alkali metals since their reaction with water forms strong bases known as alkalis. Sodium and potassium are the most common naturally found alkalis on earth.
Properties of Alkali Metals
Physical Properties:
The alkali metals have a high thermal and electrical conductivity, lustre, ductility, and malleability that are characteristic of metals. Each alkali metal atom has a single electron in its outermost shell.
They form electrovalent compounds with non-metals. The compounds that result have high melting points and are hard crystals held together by ionic bonds (resulting from mutually attractive forces between positive and negative electrical charges).
Physical Properties of Alkali Metals
Chemical Properties:
Since the alkali metals are the most electropositive (the least electronegative) of elements, they react with a great variety of nonmetals.
Reaction with Oxygen
The alkali metals tend to form ionic solids in which the alkali metal has an oxidation number of +1. Therefore, neutral compounds with oxygen can be readily classified according to the nature of the oxygen species involved.
All the alkali metals react directly with oxygen; lithium and sodium form monoxides, Li2O and Na2O, and the heavier alkali metals form superoxides, MO2. The rate of reaction with oxygen, or with air, depends upon whether the metals are in the solid or liquid state and upon the degree of mixing of the metals with the oxygen or air. In the liquid state, alkali metals can be ignited in the air with ease, generating copious quantities of heat and dense choking smoke of the oxide.
Reaction with Water
The alkali metals all react violently with water according to M + H2O → MOH + 1/2 H2. The rate of the reaction depends on the degree of metal surface presented to the liquid. With small metal droplets or thin films of alkali metal, the reaction can be explosive.
These reactions are highly exothermic (give off heat), and the hydrogen generated can react with oxygen to increase further the heat generated.
Non- metals
Non-metals are the elements of group 13-17 in which group 13-16 has 1, 2, 3, and 4 non-metals respectively. Group 17 forms a class of non-metals known as halogens. Non-metals are those which lack all the metallic attributes. They are good insulators of heat and electricity. They are mostly gases and sometimes liquid. Some are even solid at room temperatures like Carbon, sulphur and phosphorus.
Properties of non-metals
Characteristic properties of non-metals are high ionization energies and high electronegativity. Owing to these properties, non-metals usually gain electrons when reacting with other compounds, forming covalent bonds. Among the non-metals, the anionic dopants have a strong influence on the VB. Non-Metal dopants are carbon, nitrogen, fluorine, sulphur and iodine.
The following are the general properties of non-metals.
The atoms of non-metals tend to be smaller than those of metals. Several of the other properties of non-metals result from their atomic sizes.
Non-metals exhibit very low electrical conductivities. Low or non-existent electrical conductivity is the most important property that distinguishes non-metals from metals.
Non-metals have high electronegativities. This means that the atoms of non-metals have a strong tendency to attract more electrons than they would normally have.
Non-metals have high electronegativities. This means that the atoms of non-metals have a strong tendency to hold on to the electrons that already have. In contrast, metals rather easily give up one or more electrons to non-metals, metal therefore easily form positively charged ions, and metals readily conduct electricity.
Under normal conditions of temperature and pressure, some non-metals are found as gases, some found as solids and one is found as a liquid. In contrast, except mercury, all metals are solids at room temperature. The fact that so many non-metals exist as liquids or gases means that non-metals generally have relatively low melting and boiling points under normal atmospheric conditions.
In their solid state, non-metals tend to be brittle. Therefore, they lack the malleability and ductility exhibited by metals.
Physical Properties
Ductility is the property of the material to be stretched into wires but non-metals are not ductile except for carbon, as carbon fibres find uses in a wide variety of industries including sports and music equipment.
Another property characteristic of metals is absent in non-metals called malleability. They can’t be drawn into sheets as they are brittle and break on applying pressure.
They are not lustrous as they do not have any shiny appearance.
They are not sonorous and do not produce a deep ringing sound when they are hit with another material. They are also bad conductors of heat and electricity except for graphite.
Table of Non-metals
Chemical Properties
Reaction with water:
A non-metal does not react with water but it is usually very reactive in air, which is why some of them are stored in water. For example, one of the highly reactive non-metals is phosphorus and it catches fire when exposed to air that is why it is stored in water to prevent its contact with atmospheric oxygen.
Reaction with Acids
None of the non-metals is known to react with acids.
Reaction with Bases
The reaction between non-metals and bases is a very complex one. The reaction of chlorine with bases like sodium hydroxide gives products like sodium hypochlorite, sodium chloride as well as water.
Reaction with Oxygen
Oxides of non-metals are formed when it reacts with oxygen. The oxides of non-metals are acidic or neutral in nature.
When sulphur reacts with oxygen, we get sulphur dioxide.
S + O2 → SO2
When sulphur dioxide reacts with water it forms sulphurous acid.
SO2 + H2O → H2SO3
Nice summary!