CHEM101 Lecture 11: January 30: Ionization energy and reactivity, electronegativity, types of bonding, ionic vs covalent bonding, picturing covalent bond length, bond energy, and bond length.

F) Eletronegativity: Linus Pauling defined electronegativity as, The power of an atom in a molecule to attract electrons to itself. Often electronegativity is set on a relative scale. Pauling's scale assigns 4.0 to fluorine (the most electronegative element) and sets the other elements relative to uorine. Electronegativity will be discussed much more as we discuss chemical bonding and it is very useful in understanding physical properties and chemical reactivity. Figure 6: Pauling Electronegativity vs. Atom number Pauling Electronegativity vs. Atom Number 3.5 2.5 1.5 0.5 10 15 20 Atomic Number 32) Figure 6 is a plot of Pauling electronegativity vs, atomie number. Find any trend down a group and across a period and list is here. 33) Explain why these trends occur. Try to use what you know about atoms and the concepts of electron affinity and ionization energy in your explanation. 34) Why is Group 8A not included when discussing trends in electronegativity?

multiple choice (3 points each) Identify the choice that best completes the statement or answers the question. 1. Which element is the most electronegative? Cd Iodine Chlorine 2. Which of the following is true about atomic radius regarding the periodic table? Increases as you move left to right a. Increases as you go up a group d. Increases as you move down a group Increases as you move to the upper right Alkali metals on the Periodic Table have Small radii and high electronegativity 6. Large radi and high electronegativity o. Large radi and low electronegativity d Small radii and low electronegativity Which of the following best describes an atom with a high ionization energy? a. There is a weak attraction between the electrons /c It has a large atomic radius d' There is a strong attraction between the electr and the protons No attraction between electrons and protons protons Moseley arranged the periodic table a. By atomic number d Alphabetically b By atomic mass Why does adding more protons tend to decrease atomic radius? na increases the repulsion of the protons c. Increases the nuclear repulsion d Decreases the mass of the atom Increases the nuclear pull Which one of the following has the smallest radius? C. Bromine b. Sodium d, Chlorine Which of the following groups of the periodic table isthe least reactive? a. Group 1 c. Group 13 b. Group 2 d, Group 18 Which of the following gives the correct order forthe ionization energy of the elements from greatest to least? a. Cl S Al Ar Si c. Al Si S Cl Ar b. S Si CI All Ar d. Ar Cl S> Si Al The electronegativity of the elements as you increase the number of protons across a period of th table, and as you increase the number of energy levels in a group. a. Increase, increase c. Decrease, increase b. Increase, decrease d. Decrease, decrease