The first period in which you'll find 18 elementSis the fourth (4th) period: going from 19-K (potassium) to 36-Kr (Krypton).
Maybe this is the answer to the question you didn't ask but probably meant to ask.
(It is impossible for one element to contain 18 elements, you see!)
The element with 18 electrons in the 3rd period (= row) of the Periodic Table is Argon
In the first period of the periodic table there are only two elements: H (1 eln.) and He (2 eln's) and have nothing to do with the number 18.
The first row of the periodic table to have 18 elements is the third row, which ends with krypton, Kr.
two elements 2 2 2 don't forget it! its very important
Helium is in group 18 and period 1. It is the lightest of the noble gases.
The element is Helium. It has chemical symbol He.
Refer to the related link.
This element is helium.
Helium(He)
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litium, and elements in the 2nd period (row) are pretty common
The first element in a period is an alkali metal.
Period four elements fill 4s shells then 3d then 4p. The first element in this particular period is potassium.
The rows going across the periodic table are called periods. As you go across a row, each element increases in number of protons and electrons, which distinguishes it from other elements in the table.
The first element in period three of the periodic table of chemical elements is sodium (Na).
Two elements
The fourth period contains 18 elements beginning with potassium and ending with krypton – one element for each of the eighteen groups. It sees the first appearance of d-block (which includes transition metals) in the table. Do You Agree? Sincerely, Jocelyn E.Flowers
hydrogen and helium
Potassium is the element that used to be first to make fertilizer.
two elements, hydrogen and helium.
two
Period 1: 2 elements Period 2: 8 elements Period 3: 8 elements Period 4: 18 elements Period 5: 18 elements Period 6: 32 elements Period 7: 25 elements
The first period or row contains only elements that are gases at standard temperature and pressure.
A period is a horizontal row on the periodic table of the elements. There are seven periods on the periodic table. Each period corresponds to the highest energy level that contains electrons. For example, the elements in the first period have electrons in the first energy level, which is the only energy level available; the elements in the second period have their highest energy electrons in the second energy level; the elements in the third period have their highest energy electrons in the third energy level, and so on.
There are two elements in the first period, hydrogen and helium.
2