Periodic Trends Part 2

e-

e-

Positive ions are smaller than the neutral atom from which they are formed.

The increased positive charge of the nucleus pulls electrons in
closer.

e-

e-
Valence

electrons are

removed.

More protons than
electrons causes the

nucleus to pull in electrons closer.

The resulting cation
is smaller than the
neutral atom.

anion

Negative ions are larger than the neutral atom from which they are formed.

e-

e-
Valence

electrons are

added

More electrons than protons causes the ion

to expand due to increased repulsive

forces.

The resulting anion
is larger than the
neutral atom.

The extra repulsion produced from the additional electrons cause the ion to expand.

e-

e-

Cations formed

from metal atoms are smaller than
the neutral atom.

Anions formed from nonmetal atoms are

larger than the neutral atom.

1. Which of the following elements have atoms with a

smaller atomic radius than sulfur?

a. silicon

b. carbon

c. sodium

d. chlorine

2. Which ion in each pair has the smaller radius?

a. K+or Ca2+

c. Al3+or P3-

b. K+or Cs+

d. O2-or F-

Ionization Energy: the energy required to
remove an electron from an atom

Period Trend:
Ionization energy increases across the period.

As the atomic radius decreases across the period, the valence electron being removed is closer to the nucleus.

(being held more tightly!)

t

t

t

As the atomic radius increases
down the group, the valence
electron being removed is
further from the nucleus.

(easier to remove!)

Group Trend: Ionization energy decreases down the group.

Electronegativity: a measure of the ability of
an atom in a chemical compound to attract
electrons from another atom

Period Trend:
Electronegativity increases across the period.

As the atomic radius decreases across the period, the positive nuclear charge increases, making the atom’s ability to “pull in” electrons much greater.

t

t

t

As the atomic radius increases down the group, valence electrons are further from the positive nuclear charge, making it difficult for the atom to “pull in” electrons.

Group Trend: Electronegativity decreases down the group.

The element with the highest electronegativity

is fluorine. The lowest - francium

1. Which atom has the least ability to attract electrons in

a compound?

a. S

b. O

c. Cl

d. F

2. Which atom has the greatest ability to attract

electrons in a compound (electronegativity)?

a. As

c. Ga

b. Se

d. Ge

Group Trends: (down the group)
Affected by shielding. Shielding increases down the
group due to increasing number of energy levels.

Period Trends: (across the period)
Affected by increasing nuclear charge. Increasing
number of protons, but same number of energy levels.

metals

nonmetals