Comparing Electronegativity of Elements

[Vincent Grospe 3C]

Without an electronegativity chart, how can one compare electronegativities (which one is higher or lower) of elements that are diagonally close to each other (based on diagonal effect -- similar size)?

Do we begin to focus on an element's closeness to fluorine, its period, or its group which impacts the electronegativity?

[Shanmitha Arun 1L]

There are some common elements such as H, C, N, and O that we are expected to know electronegativity for in order to determine polarity. Other than that, we can base it off trends since we know electronegativity increases as we go higher up and to the right.

[905022356]

The general trend for electronegativity is that it decreases down the group and increases across the period. The elements in the p block (except the noble gasses) tend to have high values of electronegativity because they want to gain electrons to become isoelectronic with a noble gas. On the other hand, the s block elements have very low electronegativities because it's easier for them to loose electrons to gain a noble gas electronic configuration. Paulings' relative scale of electronegativity assigns these values to all elements.

[Humza_Khan_2J]

Are there any main exceptions to the electronegativity rule of increasing across a period and decreasing down a group?

[Reyna Alonso 1E]

There are a few exceptions to electronegativity, "Important exceptions of the above rules include the noble gases, lanthanides, and actinides. The noble gases possess a complete valence shell and do not usually attract electrons. The lanthanides and actinides possess more complicated chemistry that does not generally follow any trends. Therefore, noble gases, lanthanides, and actinides do not have electronegativity values.
As for the transition metals, although they have electronegativity values, there is little variance among them across the period and up and down a group. This is because their metallic properties affect their ability to attract electrons as easily as the other elements."(chem.libretexts.org)

[Scott Chin_1E]

Also, metals are known to form ionic bonds due to their tendency to give off electrons and bond with nonmetals (who more often accept electrons due to their higher electron affinity values).