<span>The characteristics of a wave are given certain names to describe them, and this helps scientists to accurately describe any given wave. The characteristic known as frequency describes the number of waves that pass a point, and it is measured in waves per second, or Hertz, which is given the symbol Hz, but can also be described using the inverse of the SI unit for second, s^-1.</span>
Acetylene is the only fuel gas suitable for gas welding because of its favourable flame characteristics of both high temperature and high propagation rates. Other fuel gases, such as propane, propylene or natural gas, produce insufficient heat input for welding but are used for cutting, torch brazing and soldering.
1) For example, sodium oxide (Na₂O).
One one molecule of sodium oxide has one sodium atome (Na) and two oxygen atoms (O).
The subscript after element shows the number of elements in a molecule.
2) Yes, it possible for two different compounds to be made from the exact same two elements.
This are isomers, same molecular formula, but different arrangements of atoms.
For example, n-butane (C₄H₁₀) and 2-methylpropane (C₄H₁₀).
3) There are large number of compounds in this world, around 40 millions.
