The periodic table is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties.
The structure of the table shows periodic trends. The seven rows of the table, called periods, generally have metals on the left and nonmetals on the right.
The columns, called groups, contain elements with similar chemical behaviours.
Deoxyribonucleic acid (DNA)
Deoxyribonucleic acid (DNA) is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.
DNA and ribonucleic acid (RNA) are nucleic acids.
Combustion is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.
Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vapourise, but when it does, a flame is a characteristic indicator of the reaction.
Chemical compound is a chemical substance composed of many identical molecules (or molecular entities) composed of atoms from more than one element held together by chemical bonds.
A molecule consisting of atoms of only one element is therefore not a compound.
There are four types of compounds, depending on how the constituent atoms are held together:
Molecules held together by covalent bonds
Ionic compounds held together by ionic bonds
Intermetallic compounds held together by metallic bonds
Certain complexes held together by coordinate covalent bonds.
Chemical Color Change
Color change may also indicate that a chemical reaction has occurred.
A reaction has occurred if two solutions are mixed and there is a color change that is not simply the result of a dilution of one of the reactant solutions.
A color change may also occur when a solid and liquid are mixed.