Periodicity

Question 1

Define and state periodic trend of Electronegativity:

Answer 1

Definition:

• Measure of an atom’s strength to attract and form bonds with electrons

Trend:

• As you move to the right across a period of elements, electronegativity increases; when the valence shell of an atom is less than half full, it requires less energy to lose an electron than gain one and thus, it is easier to lose an electron; conversely, when the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one
• As you move down a group, electronegativity decreases; this is because the atomic number increases down a group and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius

Question 2

Define and state periodic trend of Ionization Energy:

Answer 2

Definition:

• The amount of energy required to remove an electron from a neutral atom

Trend:

• The ionization energy of the elements within a period generally increases from left to right; this is due to valence shell stability
• The ionization energy of the elements within a group generally decreases from top to bottom; this is due to electron shielding

Question 3

Define and state periodic trend of Electron Affinity:

Answer 3

Definition:

• Describes the ability of an atom to accept an electron
• Unlike electronegativity, electron affinity is a quantitative measure that measures the energy change that occurs when an electron is added to a neutral gas atom; When measuring electron affinity, the more negative the value, the more of an affinity to electrons that atom has

Trend:

• Electron affinity increases from left to right within a period; this is caused by the decrease in atomic radius
• Electron affinity decreases from top to bottom within a group; this is caused by the increase in atomic radius

Question 4

Define and state periodic trend of Atomic Radius:

Answer 4

Definition:

• One-half the distance between the nuclei of two atoms

Trend:

• Atomic radius decreases from left to right within a period; this is caused by the increase in the number of protons and electrons across a period; one proton has a greater effect than one electron; thus, a lot of electrons will get pulled towards the nucleus, resulting in a smaller radius; a
• Atomic radius increases from top to bottom within a group; this is caused by electron shielding.

Question 5

Define and state periodic trend of Metallic Character:

Answer 5

Definition:

• Defined as how readily an atom can lose an electron

Trend:

• Metallic characteristics decrease from left to right across a period; this is caused by the decrease in radius of the atom which allows the outer electrons to ionize more readily
• Metallic characteristics increase down a group; electron shielding causes the atomic radius to increase thus the outer electrons ionizes more readily than electrons in smaller atoms