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.
Read more about Period 4 Element: Properties, List of Elements
Famous quotes containing the words period and/or element:
“We are in a period when old questions are settled and the new are not yet brought forward. Extreme party action, if continued in such a time, would ruin the party. Moderation is its only chance. The party out of power gains by all partisan conduct of those in power.”
—Rutherford Birchard Hayes (1822–1893)
“We must be very suspicious of the deceptions of the element of time. It takes a good deal of time to eat or to sleep, or to earn a hundred dollars, and a very little time to entertain a hope and an insight which becomes the light of our life.”
—Ralph Waldo Emerson (1803–1882)