Chapter 1Chapter 1

Activity 6: Atoms with More than one Electron

PERIODICITY There are general trends in

the properties of atoms and their ions with increasing atomic number.

These trends can be explained using the periodic table.

PERIODICITY Can you name a trend that we have

talked about this year? Think about what you graphed

Atomic Mass vs Atomic # As Atomic # increases, Atomic Mass

increases

Atomic Radius vs Atomic # As Atomic # increases, Atomic Radius

increases down a group, but decreases across a period.

Atomic Radius vs Atomic NumberA

tom

ic R

ad

ius

(pm

)

Atomic Number(protons)

Period Trend

As you proceed from left to right across a row (period), the atomic radius decreases (the atoms get smaller).

Why????

Period

The period # indicates how many energy levels the atoms in that period have.

Notice the increasing number of protons….

SO….as the number of protons increases, the outer electrons are pulled in closer to the nucleus and the

atomic radius gets smaller!

Atomic Radius vs Atomic NumberA

tom

ic R

adiu

s(p

m)

Atomic Number (protons)

Group Trend

As you proceed down a group (family or column), the atomic radius increases (the atoms get larger).

Why???

The period # indicates how many energy

levels the atoms in that period

have.

H

Li

Na

K

So…As you proceed down a group, the number of energy levels increases. This increases the atomic radii of the atoms.

Row 1

Row 2

Row 3

Row 4

http://www.youtube.com/watch?v=xjEJl88AYMohttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/atomic4.swf

Which atom is larger, Al or Si? Why????

Which atom is smaller, Br or I? Why????

Background Electrons can move between energy levels

(Bohr’s model supported by line spectra)

The nucleus and electrons are attracted to each other (opposites attract)

Electrons that are far away from the nucleus can escape the attraction of the nucleus (atoms can lose electrons)

Losing an electron is called ionization

Ionization Energy

Ionization energy is the energy required to remove a valence electron from an atom.

Valence electron= outermost electron that is farthest from the nucleus.

group

period

Ionization energy vs. atomic numberIonization energy vs. atomic number

Ca

K

H

He

Li

B

Be C

N O

F

Ne

Na

MgAl

SiP S

Cl

Ar

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14 16 18 20

Atomic Number (# of protons)

Ioni

zatio

n en

ergy

(kJ/

mol

)

Ionization Energy in kJ/mol

D

I

Ionization Energy

D

Energy needed to remove a loosely held electron from an atom

Decreases as you move down a group

Atom gets bigger, more energy levels

Nucleus is further from the outer most electron (valence electrons)

Nucleus & electron attraction decreases, so it is easier to take an electron away.

Ionization Energy

I

D

Energy needed to remove a loosely held electron from an atom

Increases as you move across a period

Nonmetals hold onto their electrons tighter

Atom is smaller, so nucleus is closer to valence electron making it harder to remove.

http://www.youtube.com/watch?v=o6tv03DR_Gg

Ionization Energy

Which has higher ionization energy?

He or Xe? (kJ/mol)

He Xe2372 kJ/mol 1170 kJ/mol

Smaller atom, He holds on tighter to valence electron

Practice

Metals have a low Ionization Energy

want to lose e-s to become stable

NonMetals have a high Ionization Energy

do not want to lose e-s, want to gain e-s

Ionization Energy

Which has higher ionization energy?

Li or Ne? (kJ/mol)

Li Ne520 kJ/mol 2081 kJ/mol

Ne holds onto atoms tighter

Practice