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  2. Period 4 element - Wikipedia

    en.wikipedia.org/wiki/Period_4_element

    A period 4 element is one of the chemical elements in the fourth row (or period) of the periodic table of the chemical 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 ...

  3. Period (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Period_(periodic_table)

    Period 4 includes the biologically essential elements potassium and calcium, and is the first period in the d-block with the lighter transition metals. These include iron , the heaviest element forged in main-sequence stars and a principal component of the Earth, as well as other important metals such as cobalt , nickel , and copper .

  4. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows ("periods") and columns ("groups"). It is an icon of chemistry and is widely used in physics and other sciences.

  5. List of time periods - Wikipedia

    en.wikipedia.org/wiki/List_of_time_periods

    The period ends with the beginning of the Age of Revolutions. Contemporary history – History within living memory. It shifts forward with the generations, and today is the span of historic events from approximately 1945 that are immediately relevant to the present time.

  6. Menstruation - Wikipedia

    en.wikipedia.org/wiki/Menstruation

    Diagram illustrating how the uterus lining builds up and breaks down during the menstrual cycle Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone ...

  7. Why Is My Period Late? 6 Possible Reasons (Besides the ... - AOL

    www.aol.com/lifestyle/why-period-6-possible...

    Elena Shlyapnikova/getty images. 1. You’ve Almost Hit Menopause. Women in perimenopause may have delayed menstrual periods due to a natural decline in ovarian function. “Perimenopause begins ...

  8. Why Do We Get ‘Period Poops’—And What to Do About Them

    www.aol.com/lifestyle/why-period-poops-them...

    If you’ve ever experienced irregular bowel movements during your period, you’re not alone. Your menstrual cycle can lead to symptoms like bloating, cramping, and changes in your bowel ...

  9. Transition metal - Wikipedia

    en.wikipedia.org/wiki/Transition_metal

    For example, Ti (Z = 22) is in period 4 so that n = 4, the first 18 electrons have the same configuration of Ar at the end of period 3, and the overall configuration is [Ar]3d 2 4s 2. The period 6 and 7 transition metals also add core (n − 2)f 14 electrons, which are omitted from the tables below.