Atomic Size, Ionization Energy, & Electronegativity

1.c. – Students know how to use the periodic table to identify alkali metals, alkaline earth metals and transition metals, trends in ionization

energy, electronegativity, and the relative sizes of ions and atoms.

PERIODIC TABLE TRENDS

PERIODIC LAW

• Mendeleev understood the ‘Periodic Law’ which states:

“WHEN ARRANGED BY INCREASING ATOMIC NUMBER, THE CHEMICAL

ELEMENTS DISPLAY A REGULAR AND REPEATING PATTERN OF CHEMICAL

AND PHYSICAL PROPERTIES”.

• Atoms with similar properties appear in groups or families (vertical columns) on the periodic table.

• They are similar because they all have the same number of valence (outer shell) electrons, which governs their chemical behavior.

PERIODIC LAW CONTINUE

Families or Groups share similar chemical and physical

properties!

Are Elements in a Row or Period Alike?

• There are several other important atomic characteristics that show predictable trends that you should know.

1. Atomic size2. Ionization Energy3. Electronegativity

PERIODIC LAW CONTINUE

• Atoms at the bottom of the periodic table are BIGGER than atoms at the top!

ATOMIC SIZE

nucleus

E1

E2

E3

E4

123456

7E6E5

E7

• As we go down a group each atom has another energy level…So the atoms get bigger.

H

Li

Na

K

Rb

• Atoms on the left side of the periodic table are bigger than atoms on the right side of the periodic table.

• As we move across a period….protons are added….this increases the nuclear charge (+)!

• As protons are added….electrons are also added….so the electrostatic attraction increases (positive & negative attraction)!

• This attraction pulls the outermost electrons in closer to the nucleus….making the atom smaller!

+ _+ _

Na Mg Al Si P S Cl Ar

• Atomic size tends to increase from right to left and from top to bottom.

Atomic Size Increases

Atom

ic S

ize

Incr

ease

s

• Ionization Energy - amount of energy needed to remove an electron from an atom.

IONIZATION ENERGY

Is it harder to take electrons from elements

that want to lose e- or

elements that wants to gain

e-?

• It is harder to remove an electron from smaller atoms because the nucleus is closer and better able to hold on to them.

• It is easier to take electrons from larger atoms because the electrons are further from the nucleus.

• It is easier to take electrons from metals since they want to LOSE electrons!

Alkali

metal HalogensNoble Gases

LOW IONIZATION

ENERGY

Medium-High IONIZATION

ENERGY

Very High IONIZATION

ENERGY

• Ionization Energy tends to increase from left to right and from bottom to top.

• Electronegativity - ability of an atom to attract an electron.

ELECTRONEGATIVITY

• It is easier for small atoms to attract an electron because the nucleus is closer and is better able to hold on to them.

• It is easier for nonmetals to gain electrons.

Which element has the highest

electronegativity?

• Electronegativity tends to increase from left to right and from bottom to top.

Putting It All TogetherMetals Metalloids

(Semimetals)Nonmetals

Left SideAlkali Alkaline Earth Transition

Elements dividing the metals and nonmetals (stair-step line)

Right SideHalogensNoble Gases

Give up (Lose) e-Cations

Give up (Lose) e- Or Accept (Gain) e-

Accept (Gain) e-

Anions

Big Atomic Size Small Atomic Size

Low Ionization High Ionization

Low Electronegativity High Electronegativity(Excluding Noble Gases)

(Noble gases do not gain e-)

Cornell Questions• As you move across a Period, how does the

atomic number change?• As you move across a Period, how does the “pull”

of the nucleus on the electrons change?• As you move across a Period, how does the

atomic size, ionization energy, and electronegativity change?

• As you move down a Group, how does the atomic size, ionization energy, and electronegativity change?

Atomic SizeIncreasesIn

crea

ses

IncreasesIn

crea

ses

Ionization Energy

Electronegativity

Create a Periodic Table Trends Periodic Table

1. Number the rows and groups2. Draw increasing arrows representing atomic

size (must be in color)3. Draw increasing arrows representing

ionization energy (must be in a different color)

4. Draw increasing arrows representing electronegativity (must be in a different color)