First ionization energy tends to decrease as you move downward and to the left on the periodic table. Of the given answer options, rubidium is the farthest down and to the left, so it has the lowest first ionization energy.

Ionization energy is a property of an atom that describes the lowest energy needed to remove a electron from its valence shell in the ground state.

Ionization energy increases up and to the right on the periodic table. All the elements listed are halogens located in group 7A of the periodic table. Because fluorine is located at the top of the periodic table in group 7A, it will have the highest first ionization energy. Ionization energy can be though of as the inverse of atomic radius. That is, the closer the valence shell of electrons is to the nucleus, the larger the magnitude of electric attractive force, and thus, the more energy is required to strip that electron. 

Ionization energy is a property of an atom or ion that describes the lowest energy needed to remove a electron from it in the ground state.

Ionization energy increases up and to the right on the periodic table. Because oxygen is the highest and rightmost element of those listed, it will have the highest first ionization energy. Ionization energy can be though of as the inverse of atomic radius. That is, the closer the valence shell of electrons is to the nucleus, the larger the magnitude of electric attractive force, and thus, the more energy is required to strip that electron.

Ionization energy is a property of an atom or ion that describes the lowest energy needed to remove a electron from it in the ground state.

Ionization energy increases up and to the right on the periodic table. Because fluorine is located furthest to the top right on the periodic table in group 7A, it will have the highest first ionization energy.

Ionization energy is a property of an atom or ion that describes the lowest energy needed to remove a electron from it in the ground state.

Ionization energy increases up and to the right on the periodic table. All the elements listed are either lower than or further to the left on the periodic table than chlorine, therefore chlorine has the highest ionization energy.

Ionization energy is a property of an atom or ion that describes the lowest energy needed to remove a electron from it in the ground state.

Ionization energy increases up and to the right on the periodic table. All the elements listed are chalcogens located in group 6A of the periodic table. Because oxygen is located furthest to the top right on the periodic table in group 6A, it will have the highest first ionization energy.

Electronegativity is the tendency for an atom to attract electrons. This tendency increases as you move upward and to the right on the periodic table. Of the given options, chlorine is the farthest up and to the right, so it is the most electronegative. The least electronegative atom would be selenium, as it is the lowest and leftmost option.

Electronegativity is a property that describes an atom's ability to attract and bond to electrons. There numerical estimates for the electronegativity of elements which differences can be used to estimate whether a bond is ionic, nonpolar covalent, or covalent. Within each period of the periodic table, there is an increase in electronegativity from left to right. Electronegativity also decreases with increasing atomic number in each group with minor exceptions among transition metals. 

Most people clearly understand that atomic radius will increase as you go down the periodic table. However, going from left to right will actually decrease atomic radius. The reason is that the increased positive charge in the nucleus from the added protons will pull the electrons closer, decreasing the radius. Of the given options, arsenic and selenium are in the lowest row, but arsenic is more to the left. As a result, it has the largest atomic radius.

The trend for atomic radius is to increase going from top to bottom, as additional valence shells are added to the atom. Out of the answer choices, rubidium has the highest energy valence shell.

With a single electron in the fifth energy level, krypton will have the highest number of energy levels of the group I elements listed.

When moving across a period, atomic radius will decrease as the number of protons increases. These protons increase the attraction between the high-energy electrons and the nucleus, effectively "shrinking" the electron cloud.