ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Electronegativity

Updated on March 30, 2015

Electronegativity refers to the ability of an atom to attract electrons that it is sharing with another atom.

The trend in electronegativity generally follows that of ionization energy and the reason for the trend is pretty much the same. Across a period (horizontal row), electronegativity increases from left to right, and within a group (vertical column), electronegativity decreases. We can also say that the trend in electronegativity is increasing towards the upper right-hand corner of the periodic table. Thus, fluorine (F) is the most electronegative element. Note that, based on the trend, Ne and He would be expected to be more electronegative than F. However, in nature, He, Ne and the other noble gases are not found sharing electrons with other atoms; they are usually ignored when discussing electronegativities.

Example: which is more electronegative: a metal or a nonmetal?
Answer: Nonmetals are more electronegative than nonmetals. Nonmetals are found on the upper right-hand corner of the periodic table.

The Pauling Scale

On the Pauling scale, atoms are assigned electronegativities ranging from 0.7 for the least electronegative atom (Francium) to 4.0 for the most electronegative atom (Fluorine); on this scale, hydrogen has an electronegativity of 2.2. Some of Pauling's original values for the most electronegative elements are given below:
F (4.0), O (3.5), N and Cl (3.0),
Br (2.8), S and C (2.5), I and Se (2.4),
P, H, and The (2.1)
Pauling later changed the value for H to 2.2. The values for the least electronegative (most "electropositive") elements are:
Cs (0.7), Rb and K (0.8), Na and B (0.9), Li, Ca and Sr (1.0), Mg (1.2), Be and Al (1.5)

For an interesting account of how Linus Pauling came up with the numbers, Click Here.

There are several other scales that have been suggested, including some that slightly modify Pauling's scale; Click Here.

Pure covalent bonding is only found in elements.
Pure covalent bonding is only found in elements. | Source

Bond Polarity

With the electronegativity difference between F and the least electronegative nonmetals being around 1.8 or 1.9, we can pretty much consider any pair of atoms that differ in electronegativity by 2.0 or higher as being in an ionic bond. Pauling defined the percent ionic character of a bond using the equation:
%ionic character = 1-exp(-x2/4),
where x is the electronegativity difference between the two atoms. Plugging in a value of 2.0 for x gives us
%ionic character = 1-exp(-2.02/4) = 0.63, or 63%
If we try to calculate the electronegativity difference between pairs of atoms, we will find that some pairs of atoms that we would normally consider to form ionic bonds (metal + nonmetal) actually have an electronegativity difference less than 2.0. These bonds between these atoms should be considered as polar covalent bonds, not ionic. Indeed, the "metal + nonmetal = ionic bond" rule is just a rule of thumb. There are a lot a of exceptions. Indeed, an entire field of study (organometallic chemistry) deals with covalently bonded transition metal atoms.

If the electronegativity difference between two atoms is larger than zero but less than 0.5, the polarization is negligible; the bond between them is classified aspolar covalent, but essentially nonpolar.

Example: classify the bond between C and H, Li and I, Na and Cl, Na and Na
Answer:
For C and H: electronegativities of C and H are 2.5 and 2.2; difference = 0.3. Bond is polar covalent, but essentially nonpolar.
For Li and I: electronegativities of Li and I are 1.0 and 2.4; difference = 1.4. The bond is polar covalent.
For Na and Cl: electronegativities of Na and Cl are 0.9 and 3.0; difference = 2.1. The bond is ionic.
For Na and Na: the electronegativity difference is obviously zero; bond is pure covalent

[Note: metallic bonding refers to bonding among atoms in a metallic solid; but the bond between just two atoms of a metallic element is pure covalent].

© 2015 Discover the World

Comments

    0 of 8192 characters used
    Post Comment

    • profile image

      Gaviota 

      3 years ago

      H2O is a polar molecule. The oxyegn carries a partially negative charge because it is more electronegative (attracts electrons more strongly) than hydrogen. The two hydrogen atoms then consequently get a partial positive charge. When water solidifies (becomes ice), the molecules have to get arranged so that the same charge interactions are at a minimum. This means that the molecules have to stop moving and they end up expanding. While water is still liquid molecules can move freely and once they repel each other they just move away. If they are about to solidify, they can't move freely anymore which is why you end up with a greater volume.If water didn't have this property, there would be no life on earth. Ice forms on top of lakes/seas/rivers and insulates the lower parts so thus it maintains the life underneath.References :

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)