Final answer:
To identify the pair with the lower electronegativity element first, we use periodic trends and specific naming rules. Electronegativity increases across a period from left to right and decreases down a group. Elements like fluorine have the highest values, while elements such as cesium have the lowest, guiding which element is listed first in a compound.
Step-by-step explanation:
The question requires us to identify the pair of elements where the element with the lower electronegativity value is listed first. Electronegativity is a measure of an atom's ability to attract and hold onto electrons when forming a chemical bond. It has distinct trends on the periodic table: it increases from left to right across a period and decreases from top to bottom within a group. From the periodic trends, we know that fluorine (F) has the highest electronegativity value and elements like cesium (Cs) are among the least electronegative.
Given that order, to identify the pair with the lower electronegativity element first, we can use the general rule that in a binary compound formula, the element with lower electronegativity is written first. We should also consider that carbon (C) is always first and hydrogen (H) follows nitrogen (N). Additionally, when there is only one atom of the first element in a molecule, the prefix "mono" is not added to that element's name, and when a prefix ends in 'a' or 'o' and the element name starts with a vowel, the 'a' or 'o' is usually omitted.
Now, knowing the general electronegativity trend from lowest (bottom left) to highest (upper right), and with fluorine having the maximum value of electronegativity, we can predict the order for a given set of elements. So, if we had to choose between pairs like Si-Cl, Sr-Se, or N-Br, we would expect Si < Cl, Sr < Se, and N < Br because Si is to the left of Cl, Sr is to the left and below Se, and N is to the left of Br on the periodic table, meaning that Silicon (Si) and Strontium (Sr) are less electronegative than Chlorine (Cl) and Selenium (Se), respectively, whereas Nitrogen (N) and Bromine (Br) have comparable electronegativities.