What is the correct order of increasing electronegativity for Rb, F and O?

Question

Quizplus · Accepted Answer

Electronegativity is a measure of an atom's ability to attract electrons towards itself in a covalent bond. 
Among these three elements, fluorine has the highest electronegativity due to its small atomic size and high effective nuclear charge. Oxygen is next in electronegativity because it has more protons in its nucleus than rubidium, making it able to attract electrons better. Rubidium has the lowest electronegativity because it has a larger atomic size and lower effective nuclear charge than the other two elements. 
Therefore, the correct order of increasing electronegativity for Rb, F, and O is Rb < O < F.

What Is the Correct Order of Increasing Electronegativity for Rb