Answer:
--> 12.011 is the relative atomic mass number of carbon.
--> elements in the same group have the same number of electrons in their outermost shells
--> elements in the same period have the same number of electron shells.
Explanation:
An element is a pure chemical substance that contains the same type of atoms which cannot be broken down into smaller substances by any chemical reaction. Example of an element is Carbon, hydrogen, Helium, Nitrogen.
Carbon has the relative atomic mass number of 12.011 in the periodic table. This is as a result of carbon having six protons, six neurons and six electrons. Carbon being an element that has isotopes, the number of decimal seen is its relative mass compared to 1/12 the mass of one atom of carbon-12.
Periodic table shows the properties of elements that vary in a regular manner. The elements in the same GROUP have the same number of electrons in their outermost shells. Electrons are arranged in shells which forms the outermost part of an atom around the atomic nucleus. Electron are arranged in shells called K,L,M,N outward from the nucleus with maximum number 2,8,18,32 respectively. For example, atoms in group 1 include hydrogen, Lithium, Sodium and potassium. When arranged in shells, they all have the same number remaining in their outermost shell which is 1. This makes them to have similar chemical properties.
Elements in the same period have the same number of electron shells. Example of elements in the same period include sodium, magnesium, aluminium silicon, phosphorus. When their atoms are arranged in shells, they have the same number of shells irrespective of the atomic number.
