Periodic Table Trends

Question 1

Electronegativity

Answer 1

Chemical property describing an atom’s ability to attract and bind with electrons.

Electronegativity increases as you move across a period. (Because elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared with the energy required to lose electrons. As a result, the elements on the left side of the periodic table generally lose electrons when forming bonds.Conversely, if the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one.)

Electronegativity decreases as you move down a group. (Because atomic number increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius.)

Flourine = most electronegative element

Question 2

Ionization Energy

Answer 2

The energy required to remove an electron from a neutral atom in its gaseous phase

Conceptually, ionization energy is the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation.

Ionization energy increases as you move across a period. (Elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled. Elements on the left side of the periodic table have low ionization energies because of their willingness to lose electrons and become cations.)

Ionization energy decreases as you move down a group. (Because the number of electrons increases and the strength of shielding increases. As a result, it is easier for valence shell electrons to ionize, and thus the ionization energy decreases down a group)

Question 3

Atomic Radius

Answer 3

Atomic radius decreases as you move across a period. (Because, within a period of elements, all electrons are added to the same shell. However, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. This means that the nucleus attracts the electrons more strongly, pulling the atom’s shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom.)

Atomic radius increases as you move down a group. (The valence electrons occupy higher levels due to the increasing quantum number (n). As a result, the valence electrons are further away from the nucleus as ‘n’ increases. Electron shielding prevents these outer electrons from being attracted to the nucleus; thus, they are loosely held, and the resulting atomic radius is large.)

Question 4

Metallic Character

Answer 4

Metallic character decreases as you move across a period. (This is caused by the decrease in radius of the atom that allows the outer electrons to ionize more readily.)

Metallic character increases as you move down a group. (Electron shielding causes the atomic radius to increase thus the outer electrons ionizes more readily than electrons in smaller atoms.)