Download Chapter 6.8 - Periodic Trends

Chapter 6.8 - Periodic Trends
Reading Sheet
1.
2.
3.
Look up the word trend in the dictionary. (See online dictionary.) A trend is _____.
a. a rule or behavior which is always followed
b. a general tendency to behave in a certain manner
c. the tendency to be modern or current
The periodic law was introduced in Chapter 2. The law states that _____.
a. all elements can be placed within the periodic table so that their properties are obvious
b. the properties of elements can be expressed mathematically as a function of atomic number
c. when making the periodic table, elements must be placed in rows periods and families
d. the properties of elements are found to be a repeating function of the atomic number
The book states that chemical properties repeat themselves at regular intervals of 2, 8, 18, and 32
elements. Why do you suppose this is? What is the magic in these numbers? (HINT: think
about what you have previous learned.)
Notes from Class Discussion:
Trends reveal the prevailing pattern.
There are always some exceptions to
trends.
The power of the modern atomic model is
in its ability to explain the magic of 2, 8, 18
and 32
Trend in atomic radius or atom size:
4.
Study Figure 6.12 and the associated text. The atomic radius is defined as ______.
a. the length of the triangle formed by three atoms
b. one-half the distance of closest approach of the atoms of an elemental substance
c. one-half the length of the diagonal of the square formed by five atoms
d. the distance between the centers of any two adjacent atoms
Across period:
5.
Analyze Figure 6.13 and the associated text. The atomic radius of main-group elements (does
not include transition metals) shows the general trend of _____. Pick two.
a. increasing when progressing across a row from left to right
b. decreasing when progressing across a row from left to right
c. increasing when progressing down a column from top to bottom
d. decreasing when progressing down a column from top to bottom
Down a group:
6.
Electrons in the orbitals are attracted to the protons in the nucleus. One might think that each
electron in the Na atom would experience the pull of all 11 of its electrons. But this is not the
case. The effective nuclear charge is less than 11 due to shielding effects. Which of the
following statements correctly describe the effect of shielding? Select all that apply.
a. Electrons closer to the nucleus shield more distant electrons from the + nuclear charge.
b. When moving across a row of the P.T., the effective nuclear charge experienced by outer
electrons steadily increases.
c. The electrons experiencing the least amount of shielding are those in the n=1 energy level.
7.
What explains the trend observed in the atomic radius when moving across a row?
a. The principal quantum # (n) of the largest orbitals increases; e- are entering these orbitals.
b. The principal quantum # (n) of the largest orbitals decreases; e- are entering these orbitals.
c. The effective nuclear charge is decreasing while the n of the largest orbitals is not changing.
d. The effective nuclear charge is increasing while the n of the largest orbitals is not changing.
Explaining the trend in size:
Effective nuclear charge
8.
What explains the trend observed in the atomic radius when moving down a column?
a. The principal quantum # (n) of the largest orbitals increases; e- are entering these orbitals.
b. The principal quantum # (n) of the largest orbitals decreases; e- are entering these orbitals.
c. The effective nuclear charge is decreasing while the n of the largest orbitals is not changing.
d. The effective nuclear charge is increasing while the n of the largest orbitals is not changing.
9.
Which of the following series of atoms and ions are isoelectronic? (If necessary, review pp.
150-151.)
a. Li, Na, K
b. Li+, Na+, K+
c. F, Ne, Na
d. F-, Ne, Na+
10.
In which of the following listing is the largest species listed first? Select all that apply.
a. Ne, He
b. Na, Mg
c. Na, Na+
d. Cl, Cl-
11.
Consider two particles (one being a neutral atom and the other being an ion) with the same
number of electrons, each present in the ground state. Which particle would be largest?
a. The particle with the outermost electrons in the highest energy level.
b. The particle with the outermost electrons in the lowest energy level.
c. The particle with the greatest number of protons.
d. The particle with the least number of protons.
12.
Consider the sodium ion (Na+) and the neon atom (Ne). Which is the smallest particle and
why?
a. The Na+ ion; it has more electrons.
b. The Na+ ion; it has more protons.
c. The Ne atom; it has less protons.
d. The Ne atom; it's outermost electrons are at the n=2 energy level.
e. The Na+ ion; it's outermost electrons are at the n=2 energy level.
13.
If an element has a high ionization energy, then which of the following would be true about it?
a. It tends to form ions with a lot of charge.
b. It takes a lot of energy to remove an electron.
c. It tends to easily form + ions.
d. It has a lot of energy when it is ionized.
14.
Analyze Figure 6.15 and the associated text. The ionization energy of main-group elements
(does not include transition metals) shows the general trend of _____. Pick two.
a. increasing when progressing across a row from left to right
b. decreasing when progressing across a row from left to right
c. increasing when progressing down a column from top to bottom
d. decreasing when progressing down a column from top to bottom
15.
The larger the atom, the more likely that it will have a _____ ionization energy.
a. higher
b. lower
16.
The property of an element which describes the tendency of its atom to attract to itself the
electrons which are present in a covalent bond is known as the ______.
a. ionization energy b. valence
c. electron affinity
d. electronegativity
17.
The element with the greatest electronegativity is ______ and the element with the lowest
electronegativity (which is a tie) is ______. List an elemental symbol in each blank.
isoelectronic
Trend in ion size:
Cations (+ ions):
Compare Ne, Na+, Mg2+, Al3+
Anions (- ions):
Compare N3-, O2-, F- and Ne
Ionization energy - know definition
Trend in ionization energy:
Across period:
Down a group:
Electronegativity - know definition
Trend in electronegativity: