Ionization+energy,+Electron+Affinity,+Atomic+Radius

$$$$ $$$ $$$  Ionization Energy, elctron affinity and atomic radius

__Ionization Energy__  "Ionization energy is the energy required to remove an electron from a neutral atom" (Text. P168)

__ Electron Affinity __ "Electron affinity is how easy to add an electron to a neutral atom" and "The energy released when an electron is added to an atom." $

__ Atomic Radius __ $$ "Atomic radius is a term used to describe the size of the [|atom] ."

These three concepts are important __when forming chemical bonds.__ For example, alkali metals only have one electron on the outermost shell, so the required ionization energy is the minimum because the atoms on the right has minimum electrons in a group, so they are easy to react.

$ "The IONIZATION ENERGY of an atom is equal to __the amount of energy given off__ when an electron is added to an atom. When an electron is added to an atom, we call the energy given off the ELECTRON AFFINITY (EA). So, IE=EA."

__Notes:__ Before we explain the trend of ionization energy, electron affinity, and atomic radius, let us review some concepts about __ electrostatic force __ together. opposite charges attract each other like charges repel each other the greater the distance between two charged particles, the smaller the attractive(or replusive) force existing between them” the greater the charge on two particles, the greater the force of attraction(or replusion) between them

__Question 1 __: What is the trend of ionization energy ？ Why it performs in this way? Answer: ① When elements go to the right of the periodic table in a group, ionization energy increases; as elements go down a family, ionization energy decreases. ② As elements go right in a same group, the atomic number increases with same number of shells, so the nuclei of these elements will possess more positive charges. Then the nuclei will be able to attract electrons more tightly according to the rules of __ electrostatic forces __ 1 and 4. As a result, more energy will be needed to remove an electron from a neutral atom which is on the right compared to its left one.As elements go down a family, there is one more shells added gradually, so the distance between the nuclei and the electrons become bigger and bigger. According to the rule of __ electrostatic forces __ 1, the attractive forces between nuclei and electrons decrease. (Although the proton number increases as elements go down, the distance is so large that these added protons don’t make a difference)As a result, less energy is needed when one more shell is added, so the ionization energy decreases.

__ Question 2: __ What is the trend of electron affinity? Why it acts in this way? Answer: When elements go to the right of the periodic table in a group, electron affinity increases; as elements go down a family, electron affinity decreases. <span style="font-family: 宋体; font-size: 14pt; line-height: 150%;">② <span style="font-family: 'Calibri','sans-serif'; font-size: 14pt; line-height: 150%;">As elements go right in a same group, the atomic number increases with same number of shells, so the nuclei of these elements will possess more positive charges. Then the nuclei will be able to attract electrons more tightly according to the rules of __ electrostatic forces __ 1 and 4. As a result, an electron is easier to be added to a neutral atom which is on the right compared to its left one.

As elements go down a family, there is one more shells added gradually, so the distance between the nuclei and the electrons become bigger and bigger. According to the rule of __ electrostatic forces __ 1, the attractive forces between nuclei and electrons decrease. (Although the proton number increases as elements go down, the distance is so large that these added protons don’t make a difference)As a result, it will be harder to add an electron to an element which is placed at the bottom, so the electron affinity decreases. __ Question 3 __ : What’s the trend of atomic radius? Why it acts in this way? Answer: <span style="font-family: 宋体; font-size: 14pt; line-height: 150%;">① <span style="font-family: 'Calibri','sans-serif'; font-size: 14pt; line-height: 150%;">When elements go to the right of the periodic table in a group, atomic radius decreases; as elements go down a family, atomic radius increases. <span style="font-family: 宋体; font-size: 14pt; line-height: 150%;">② <span style="font-family: 'Calibri','sans-serif'; font-size: 14pt; line-height: 150%;">As elements go right in a same group, the atomic number increases with same number of shells, so the nuclei of these elements will possess more positive charges. Then the nuclei will be able to attract electrons more tightly according to the rules of __ electrostatic forces __ 1 and 4. As a result, the atomic radius is decreasing as elements going right.

As elements go down a family, there is one more shells added gradually, so the distance between the nuclei and the electrons become bigger and bigger, and in addition, according to the rule of __ electrostatic forces __ 1, the attractive forces between nuclei and electrons decrease. (Although the proton number increases as elements go down, the distance is so large that these added protons don’t make a difference), so the distance becomes even larger. As a result, the atomic radius increases when elements go down a family.

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