<P> A period 4 element is one of the chemical elements in the fourth row ( or period ) of the periodic table of the elements . The periodic table is laid out in rows to illustrate recurring ( periodic ) trends in the chemical behaviour of the elements as their atomic number increases : a new row is begun when chemical behaviour begins to repeat , meaning that elements with similar behaviour fall into the same vertical columns . The fourth period contains 18 elements , beginning with potassium and ending with krypton . As a rule , period 4 elements fill their 4s shells first , then their 3d and 4p shells , in that order ; however , there are exceptions , such as chromium . </P>
<P> A period 4 element is one of the chemical elements in the fourth row ( or period ) of the periodic table of the elements . The periodic table is laid out in rows to illustrate recurring ( periodic ) trends in the chemical behaviour of the elements as their atomic number increases : a new row is begun when chemical behaviour begins to repeat , meaning that elements with similar behaviour fall into the same vertical columns . The fourth period contains 18 elements , beginning with potassium and ending with krypton . As a rule , period 4 elements fill their 4s shells first , then their 3d and 4p shells , in that order ; however , there are exceptions , such as chromium . </P>
which element begins the fourth group of the periodic table
which element begins the fourth group of the periodic table
potassium
potassium