Answer:
Step-by-step explanation:
Elements are listed in numerical order by atomic number. The atomic number is the number of protons in an atom of that element. So element number 1 (hydrogen) is the first element. Every atom of hydrogen has 1 proton. Until a new element is discovered, the last element on the table is element number 118. Every atom of element 118 has 118 protons. This is the biggest difference between today's periodic table and Mendeleev's periodic table. The original table organized the elements by increasing atomic weight.
Each horizontal row on the periodic table is called a period. There are seven periods on the periodic table. Elements in the same period all have the same electron ground state energy level. As you move from left to right across a period, elements transition from displaying metal characteristics toward nonmetallic properties.
Each vertical column on the periodic table is called a group. Elements belonging to one of the 18 groups will share similar properties. Atoms of each element within a group have the same number of electrons in their outermost electron shell. For example, elements of the halogen group all have a valence of -1 and are highly reactive.
There are two rows of elements found below the main body of the periodic table. They are placed there because there wasn't room to put them where they should go. These rows of elements, the lanthanides and actinides, are special transition metals. The top row goes with period 6, while the bottom row goes with period 7.
Each element has its tile or cell in the periodic table. The exact information given for the element varies, but there is always the atomic number, the symbol for the element, and the atomic weight. The element symbol is a shorthand notation that is either one capital letter or a capital letter and a lowercase letter. The exception is the elements at the very end of the periodic table, which have placeholder names (until they are officially discovered and named) and three-letter symbols.
The two main types of elements are metals and nonmetals. There are also elements with properties intermediate between metals and nonmetals. These elements are called metalloids or semimetals. Examples of groups of elements that are metals include alkali metals, alkaline earths, basic metals, and transition metals. Examples of groups of elements that are nonmetals are the nonmetals (of course), the halogens, and the noble gases.