Period 3 Elements Pdf
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A period on the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, elements in the same group (column) have similar chemical and physical properties, reflecting the periodic law. For example, the halogens lie in the second-to-last group (group 17) and share similar properties, such as high reactivity and the tendency to gain one electron to arrive at a noble-gas electronic configuration. As of 2022[update], a total of 118 elements have been discovered and confirmed.
Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomic number increases, shells fill with electrons in approximately the order shown in the ordering rule diagram. The filling of each shell corresponds to a row in the table.
In the s-block and p-block of the periodic table, elements within the same period generally do not exhibit trends and similarities in properties (vertical trends down groups are more significant). However, in the d-block, trends across periods become significant, and in the f-block elements show a high degree of similarity across periods.
There are currently seven complete periods in the periodic table, comprising the 118 known elements. Any new elements will be placed into an eighth period; see extended periodic table. The elements are colour-coded below by their block: red for the s-block, yellow for the p-block, blue for the d-block, and green for the f-block.
The first period contains fewer elements than any other, with only two, hydrogen and helium. They therefore do not follow the octet rule, but rather a duplet rule. Chemically, helium behaves like a noble gas, and thus is taken to be part of the group 18 elements. However, in terms of its nuclear structure it belongs to the s-block, and is therefore sometimes classified as a group 2 element, or simultaneously both 2 and 18. Hydrogen readily loses and gains an electron, and so behaves chemically as both a group 1 and a group 17 element.
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. Almost all have biological roles.
Period 5 has the same number of elements as period 4 and follows the same general structure but with one more post transition metal and one fewer nonmetal. Of the three heaviest elements with biological roles, two (molybdenum and iodine) are in this period; tungsten, in period 6, is heavier, along with several of the early lanthanides. Period 5 also includes technetium, the lightest exclusively radioactive element.
Period 6 is the first period to include the f-block, with the lanthanides (also known as the rare earth elements), and includes the heaviest stable elements. Many of these heavy metals are toxic and some are radioactive, but platinum and gold are largely inert.
All elements of period 7 are radioactive. This period contains the heaviest element which occurs naturally on Earth, plutonium. All of the subsequent elements in the period have been synthesized artificially. Whilst five of these (from americium to einsteinium) are now available in macroscopic quantities, most are extremely rare, having only been prepared in microgram amounts or less. Some of the later elements have only ever been identified in laboratories in quantities of a few atoms at a time.
No element of the eighth period has yet been synthesized. A g-block is predicted. It is not clear if all elements predicted for the eighth period are in fact physically possible. There may therefore be no ninth period.
The periodic table is the most important reference a chemist has because it puts all the known elements into a meaningful pattern. Elements are arranged left to right and top to bottom in order of increasing atomic number. This order generally goes with increasing atomic mass.
The different rows of elements are called periods. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state). The number of elements in a period increases as one moves down the periodic table because as the energy level of the atom increases, the number of energy sub-levels per energy level increases.
A group is a vertical column of the periodic table, based on the organization of the outer shell electrons. There are a total of 18 groups. There are two different numbering systems that are commonly used to designate groups, and you should be familiar with both. The traditional system used in the United States involves the use of the letters A and B. The first two groups are 1A and 2A, while the last six groups are 3A through 8A. The middle groups use B in their titles. Unfortunately, there was a slightly different system in place in Europe. To eliminate confusion, the International Union of Pure and Applied Chemistry (IUPAC) decided that the official system for numbering groups would be a simple 1 through 18 from left to right. Many periodic tables show both systems simultaneously.
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However, how do I use jQuery to select the drop down list so that I can pre-fill it? I realize that I could do this server side but there will be other dynamic elements on the page that affect the list.
A backslash in a jQuery selector escapes the next character. But you need two of them because backslash is also the escape character for JavaScript strings. The first backslash escapes the second one, giving you one actual backslash in your string - which then escapes the next character for jQuery.
As noted in bdukes answer, there is a reason we need 2 \ characters. \ will escape the following character in JavaScript. Se when JavaScript interprets the string "#Address\.Country", it will see the \, interpret it to mean take the following character litterally and remove it when the string is passed in as the argument to $(). That means jQuery will still see the string as "#Address.Country".
That's where the second \ comes in to play. The first one tells JavaScript to interpret the second as a literal (non-special) character. This means the second will be seen by jQuery and understand that the following . character is a literal character.
Until the issue is fixed, I use my own extension methods like Html.TextBoxFixed, etc. that simply replaces dots with underscores in the id attribute (not in the name attribute), so that you use jquery like $("#Address_Street") but on the server, it's like Address.Street.
When I run this code no options are selected in the drop-down. I believe the problem I am having is caused by the fact that I have an HTML element with a period in the id but I do not have the ability to change the underling HTML code for the page.
In CSS selector frameworks, including jQuery/Sizzle and what Selenium is doing in this example, the period has a special meaning - mainly to select elements based on many rules. This is why it's tripping here here - you can see the same thing if you run the CSS selector direct into Chrome or Firebug - it will fall over as well.
I think it will work quite well to just use the same data element in different datasets with different periodicity. The only thing to look out for is to avoid double counting, e.g. watch out for misleading Totals in Analytics.
Data elements should not be assigned to two separate data sets whose period types differ. The recommended approach would be to create two separate data elements (for instance a monthly and yearly data element) and assign these to respective datasets.
I am sure Lars can provide the exact reason for this, but I am pretty sure one should not have the same data element with two separate frequencies. It would seem to be a good feature however, but I believe this is a restriction imposed by analytics at the moment.
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