Arsenic (As) is a 33-atom chemical element that is primarily found in the Earth's crust and rocks. It is a toxic metal that can cause cancer and other health problems in animals, people and plants.
The number of valence electrons in an element tells us how likely it is to form a chemical molecule from that element. A valence electron is an unpaired electron in the outermost shell of the element.
An example of valency is arsenic acid, which forms 3 bonds with the oxygen atoms in water and one bond with each hydrogen atom. The molecule also has a double bond with the arsenic atom.
In water, the H+ ions and the OH- ions are both very close to the same molar concentration. That's because when an acid loses a proton, it becomes an ionized molecule with a negative charge.
When the pH of a solution is near neutral, the OH- ions are much higher than the H+ ions. This causes the ionized molecules to be more mobile in the water.
This is why some acid solutions are toxic, like sulfuric acid, which can kill humans. It's also why some water is neutral, even though it has a very low concentration of H+ ions.
The valency of an element is a very important property for determining how the elements interact with each other and with other elements. It is also a key property for understanding how chemical reactions take place in the world.