The atomic number refers to the number of protons present in the nucleus of an atom. It is denoted by the symbol "Z" and is a fundamental property of an element. Each element on the periodic table has a unique atomic number, which determines its position in the periodic table and its identity.
The atomic number is important because it defines the element's characteristics and properties. It determines the number of electrons an atom has when it is in its neutral state. In a neutral atom, the number of protons (positive charges) is equal to the number of electrons (negative charges), ensuring overall electrical neutrality.
Valency, on the other hand, refers to the combining capacity or the number of electrons an atom can gain, lose, or share in order to achieve a stable, filled outer electron shell. The valency of an element is determined by its position in the periodic table, specifically by the number of valence electrons it possesses.
Valence electrons are the electrons present in the outermost shell or energy level of an atom. These electrons are involved in chemical reactions and determine how an atom interacts with other atoms to form compounds. The valency of an element determines its ability to form bonds with other elements and influences the types of compounds it can form.
Valency is often indicated by the number of electrons an atom needs to gain or lose to achieve a stable electron configuration, typically the configuration of a noble gas. For example, an element with a valency of 2 would need to gain or lose two electrons to achieve stability. The valency of an element can vary depending on the type of compound it forms and the chemical reaction it undergoes.