PERIODIC TRENDS

Chemistry 11 – Unit 5 Forero Name: ______________________________ Date: ___________ Blk: _____
NOTES: PERIODIC TRENDS
Examine your periodic table to answer these questions and fill-in-the-blanks. Use
drawings to support your answers where needed:
I. ATOMIC RADIUS (Size)
Going from left to right a given period, the atomic number (# of ___________________)
increases/decreases (circle one). Thus, the positive charge on the nucleus ____________.
This trend also brings an increase in the number of _________________ surrounding the
nucleus.
1. What would happen to the atomic radius as the number of electron “shells” increases?
Why? Then, what should happen to the atomic radius going DOWN a group?
2. (a) What happens to the size of the positive nuclear charge “felt” by the electrons
surrounding the nucleus in an element, going from left to right across a row of the table?
(b) What effect would you expect this change in charge to have on the average distance
between the nucleus and a given electron going across the table?
(c) What should happen to the radii of the elements, going from left to right
ACROSS a row of the periodic table?
Chemistry 11 – Unit 5 Forero II. IONIZATION ENERGY
Ionization Energy: energy required to REMOVE an electron from a neutral atom
*The e- removed is the outermost and therefore the most easily removed
1. (a) What happens to the distance between the nucleus and outermost electrons going
DOWN a chemical family?
(b) What happens to the electrostatic attraction of the nucleus to an electron in the
outermost shell going DOWN a family?
(c) Thus, what happens to the ionization energy going DOWN a family?
2. (a) What happens to the distance between the nucleus and outermost electrons going
ACROSS a period? (refer to above section on atomic radius!)
(b) What happens to the nuclear charge going ACROSS the period?
(c) What happens to the electrostatic attraction of the nucleus to an electron in the
outermost shell going ACROSS a period?
(d) Thus, what happens to the ionization energy going ACROSS a period?
3. What member of each of the following pairs should have a greater ionization energy?
(a) Br or Cl
(b) Al or Cl
(c) Ne or Xe (d) Mg or Ba (e) F or Ne
(f) Rb or I
Chemistry 11 – Unit 5 Forero Extension Questions: Answer the following questions based on the graph you’ve made of
ionization energy versus atomic number.
1. Why are the ionization energies for He, Ne and Ar so high?
2. Why do the ionization energies decrease going from He to Ne to Ar?
3. Why is there a general increase in ionization energy going from Li to Ne?
4. “Filled subshells and half-filled subshells have special stability which requires extra
energy to be applied before electron removal can occur”. This general statement is
supported by the existence of the electron configuration exceptions found for Cu and CR.
What experimental evidence exists in the graph to support this general statement?
Chemistry 11 – Unit 5 Forero III. ELECTRONEGATIVITY
Electronegativity: the tendency of an atom to attract electrons from a neighbouring atom.
*The investigation of electronegativity focuses on the atoms Li, F and I.
1. This exercise compares Li and F:
(a) Which atom is larger: Li or F? (refer to above section on atomic radius!)
(b) Which atom has the stronger attraction to the outer electrons on a neighbouring atom
based ONLY on atomic radius? WHY?
(c) Which atom has the greater nuclear charge?
(d) Which atom can attract electrons from an adjacent atom most strongly based on
BOTH size and nuclear charge? WHY?
(e) Summarize the above by filling in the blank below.
IN GENERAL, when going from left to right across the periodic table the
electronegativity of the atoms will _______________________________.
2. This exercise compares F and I:
(a) Which atom is larger: F or I?
(b) Which atom has a stronger attraction to the outer electrons of another atom? WHY?
(e) Summarize the above by filling in the blank below.
IN GENERAL, when going from going down a family of the periodic table the
electronegativity of the atoms will _______________________________.
Chemistry 11 – Unit 5 Forero If an atom has HIGH electronegativity, it has a high/low (circle one) ionization energy.
WHY?
If an atom has LOW electronegativity, it has a high/low (circle one) ionization energy.
WHY?