The Periodic Law (Periodic Table)

Brief History of periodic table Original periodic table was constructed by Dmitri Mendeleev in 1869. This periodic table consisted of about 60 elements and was arranged in order of increasing atomic mass

Modern Periodic Table Current periodic table is based on the work of Henry Mosely, who arranged the elements in order of increasing atomic number in 1914.

Periodic Trends Periodic Law: This means that if elements are arranged by atomic #, they will fall into groups that have similar properties. You will see patterns form like the Valence electron pattern that you found yesterday. Trending happens due to Periodic Law

Periodic Trends You will be responsible for knowing 3 trends: Periodic Trends are patterns that are increasing and decreasing in nature as you go across and down the table. For example: the valence electrons increase as you go to the right across the table and stay the same as you go down. You will be responsible for knowing 3 trends: Atomic Radii 1st Ionization Energy Electronegativity You will also be responsible for knowing how an ions radii compares to a neutral atoms radii. #of Valence Electrons Increase Stay the same

Atomic Radii Atomic Radii-The distance from the center of the nucleus to the edge of the atom’s electron cloud. Atomic Radii

Atomic Radii Continued Trend in each period Why do you think the radius decreases to the right if there are more protons to the right? Shouldn’t that make the radius increase? As there are more protons they pull more strongly on the electrons that are surrounding them and each period is within the same energy level.

Atomic Radii Continued Trend in each group Why do you think the radius increases as you go down a group if more protons means they pull harder on the electrons? As you go down a group you are adding energy levels which makes the radius increase. You can only squish the shielding electrons in so close together.

Atomic Radii Continued Periodic Table Trend: Increases to the left Increases going down Increasing Size

Atomic Radii Practice K or Ni Ne or Xe Rb or In Al, K, Ne, H In each pair which of the following has the largest Atomic Radii? K or Ni Ne or Xe Rb or In Arrange the following in order of increasing atomic radii? Al, K, Ne, H Will a larger atomic radii make an atom more or less likely to give away an electron? You will find you answer in the next trend!!

Ionization Energy (IE) 1st Ionization Energy-Energy required to remove one electron from an un-bonded atom. (individual atoms) Basically: How hard is it to get an electron away from an atom? Gimme that!!! Mine! e-

Ionization Energy (IE) Continued Trend across a period? Decreases to the left Trend in a group/family? Decreases going down Which Group would have the lowest first Ionization energy? (who is it easiest to take an electron from?) Group 1 Why? They want to get rid of that 1 valence electron to reveal a full energy level underneath. Valence electrons are further away from nucleus than other groups of elements so there is less pull on the valence electrons by the protons in the nucleus. There are more shielding or inner elctrons.

Ionization Energy (IE) Continued Which group would have the highest first ionization energy? Group 18 Why? They do not want to lose one of their 8 valence electrons (they are happy the way they are with a full outer energy level) Their valence electrons are closer to the nucleus than other groups are therefore the protons in the nucleus can pull more strongly on the electrons. Less shielding or inner electrons in the way.

Ionization Energy Periodic Table Trend: Decreases to the left Decreases going down Decreasing Decreasing

Ionization energy practice Which element within the following pairs has the highest ionization energy? K or Be B or Ga O or Ca Ar or Sb Arrange the following in decreasing Ionization energy Be, O, B, Rb, Ar, F

Electron Affinity Electron Affinity-The energy change that occurs when an individual atom gains an electron. The more an atom “loves” getting another electron the more the energy it will release. . . _ . . + Electron Atom

Electron Affinity Which group is “happiest” to take on an electron?

Electron Affinity Why would Group 17 elements give off so much energy when they get an additional electron? 1 more electron will make them more stable and fill there outer shell for a total of 8. Also, the valence electrons are closer to the nucleus than in other atoms and therefore the protons can pull more strongly on the electrons.

Electron Affinity Which groups care nothing for additional electrons?

Electron Affinity Group 1 and Group 18 and 2? Why? Group 18 elements are totally happy with their 8 electrons and are very stable. These elements do not want to give up valence electrons. Group 1 is closer to being “happy” by giving away its 1 valance electron to reveal a full valence shell underneath. So, gaining an extra electron makes them more unstable than they already are. Group 2 has a full s orbital and a full s orbital is more stable than a partially full p orbital.

Electron Affinity Periodic Table Trend: Decreases to the left Decreases going down Decreasing Decreasing

Electron Affinity Arrange by increasing Electron Affinity Which of the following has the greatest electron affinity? Al or Br O or C Xe or F Arrange by increasing Electron Affinity Cl, K, Fr, I

Electronegativity Electronegativity-How strongly one atom attracts the electrons of another atom in a compound (in a bond). Developed by Linus Pauling Electronegativity is used to predict the types of bonds that elements will form. Which element do you think would be the most electronegative?

Electronegativity Fluorine has the highest electronegativity due to: Its small radius (ability of the protons to pull on the valence electrons). Its near full valence shell causes this atom to be highly unstable, therefore, gaining an electron will be highly desirable. It would stabilize the atom and give it a full valence shell.

Electronegativity Fluorine is the most electronegative with an electronegativity of 4.0. All other values are calculated in relation to Fluorine’s value. Scientists just picked the number 4 and went from there. It’s not as much a measurement as a comparison of each element’s pull on electrons in a bond to fluorine’s pull on electrons in a bond. Basically…who is the biggest electron hog and will fight the most for them!!

Electronegativity & (FON) Oxygen, Nitrogen and then the other halogens are the most Electronegative after fluorine. F, O, N – Top 3 highest electronegativity

Electronegativity Periodic Table Trend: Decreases to the left Decreases going down Decreasing Decreasing

Electronegativity Practice Which of each pair has the greatest EN? a. Ca or Ga b. Br or As c. Li or O d. Ba or Sr e. Cl or S f. O or S Rank the following elements by increasing EN: sulfur, oxygen, neon, aluminum, Francium, Potassium