Elements within a group have the same number of valence electrons, but in increasing energy levels. Elements toward the bottom of a group have valence electrons with higher energies in larger orbitals. This results in a larger radius and a weaker attractive force between the nucleus and outer electrons. The ionization energy decreases as the electrons are more removed from the attraction of the nucleus.

When moving down a group, atomic radius increases and ionization energy decreases.

Atomic radius increases with increasing effective nuclear charge (Z). Elements toward the right and toward the top of the periodic table have the highest Z values. Protons and electrons are added in pairs as we traverse the periodic table from left to right. A attractive force is established between the positively-charged nucleus and the negatively-charged electron cloud, which increases as the number of particles grows.

When electrons are added or taken away without the same happening to a proton, an imbalance of charge accumulates. When more electrons are present than normal, the electron cloud sags farther away from the nucleus. When fewer electrons are present than normal, the electron cloud is drawn in more tightly toward the nucleus. Atoms with extra electrons (a negative charge) will have larger nuclei than their neutral counterparts. A chloride ion will thus has a larger atomic radius than argon, a potassium ion, or a calcium ion.

Atomic radius can be determined using the periodic trends. Atomic radius increases to the left of a period and down a group of the periodic table. Electronegativity, in contrast, increases to the right of a period and up a group of the periodic table. Relating the two, we can see that the greater the atomic radius, the weaker its electronegativity because the electrons are farther away from the nucleus and are unable to feel the attractive force of the protons in the nucleus.

Electronegativity increases to the right and up when looking at the periodic table of elements, such that fourine is the most electronegative element. Following this general trend can help you determine the relative electronegativity between atoms within problems. Remember that periods run horizontally on the table and groups run vertically.

Remember that electronegativity increases as you approach the top right corner of the periodic table. Since oxygen is the farthest right and the highest up on the perioidic table out of these choices, we conclude that it has the highest electronegativity.

Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and from the bottom of a group to top. The least electronegative (sometimes called most electropositive) element is francium (Fr). This is because an electron that can be attracted to francium has the lowest ratio of attractive nuclear force to repulsive force by other electrons in the atom. Essentially, the distance between the attractive nuclear protons is too great for the attractive force to overcome the repulsion of the orbiting electron cloud. Francium will not be stable if it gains an electron, and is much more stable if it loses an electron and forms an octet as a positive ion.

Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and the bottom of each group to the top. The most electronegative element is fluorine (F). This is because an electron that can be attracted to fluorine has the greatest ratio of attractive nuclear force to repulsive force by other electrons. Essentially, fluorine is the most stable ion with a negative-one charge. It is small, allowing the nuclear protons to maintain the attractive force on the electron, and it has an octet, giving it the absolute maximum ionic stability possible.

The correct answer is chlorine. The most electronegative elements are those in the upper right of the periodic table, with the exception of the noble gases. Electronegativity describes how easily an element will gain an electron. The halogens (second to last group) "want" an extra electron to complete their valence shell. Iodine and chlorine are both halogens. Chlorine, however, has a smaller atomic radius, and therefore a smaller distance between the protons and outer electrons. Chlorine thus has a stronger attraction for an additional electron due to the greater effective nuclear attraction.

Electronegativity is the tendency for an atom to attract electrons.

We know that fluorine is the most electronegative atom on the periodic table, and that electronegativity increases to the right across periods and upwards within groups. The trick answer might possible be potassium, since it has a very low electronegativity and is located to the left of the table. The noble gases, however, have virtually no electronegativity. Remember, noble gases are characterized by their valence octets in the ground state. This stability generates resistance to any electron change, including both electronegativity and ionization energy.

Flourine must have an electronegativity value higher than oxygen. Remember your periodic trends: electronegativity increases as we move up and to the right on the periodic table. We are told in the passage that the electronegativity of oxygen is 3.44, therefore, our answer must be 3.9.