Questions

1. Lichens are plants that grow in exposed places such as rocks or tree bark.

2.  Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere.  

3. They need to be very good at absorbing water and nutrients to grow there.

Helium has the highest First Ionization Energy in the Noble Gases group.

Ionization Energy ::

Ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms. Atoms are more stable when they have full valence shells.

Noble Gases have a very stable electron configuration, therefore, they have the highest amount of ionization energy within their periods. It decreases down a family because electrons farther from the nucleus are easier to remove.

Ionization Energy levels of Noble Gases group in Descending Order :: He, Ne, Ar, Kr, Xe, Rn

Later in 1840, Rowland Hill invented the stamp, which was paid for by the sender, not the receiver.