Periodic Relationships Among the Elements

Chapter 5

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History of the Periodic Table

•Arranged the elements by increasing ATOMIC MASS and saw a periodic repetition of properties

•Produced the first PERIODIC TABLE – 1871•The table placed elements with similar properties in the same column

•Kept “holes” for undiscovered elements, and predicted the properties in advance

Dimitri Mendeleev

Mendeleev’s Periodic Table

Properties of elements predicted by Mendeleev

H.G. Moseley in 1914

• Rearranged the elements by:ATOMIC NUMBER

• This has become theMODERN PERIODIC TABLE

Electrons and Ions on the Periodic Table

Review: Valence Electrons

What are valence electrons?

*Remember: Elements in a group have similar properties because they have the same valence electron configuration

Valence Electron Configuration

Group e- config Valence electrons

Expected Charges

1 ns1

2 ns2

13 ns2np1

14 ns2np2

15 ns2np3

16 ns2np4

17 ns2np5

18 ns2np6

+1

+2

+3 -1-2-3

Charges Of Representative Elements

8.2

Na+

Al3+

F-

O2-

N3-

What ions are isoelectronic with Neon?

Isoelectronic: Elements and ions that have the same number of electrons and therefore the same electron configuration

Mg2+

What would the electron configuration be?___________

When a cation is formed from an atom of a transition metal, electrons are always removed first from the s orbital and then from the d orbitals.

Fe: [Ar]4s23d6

Fe2+: [Ar]4s03d6 or [Ar]3d6

Fe3+: [Ar]4s03d5 or [Ar]3d5

Mn: [Ar]4s23d5

Mn2+: [Ar]4s03d5 or [Ar]3d5

Forming Ions with Transition Metals

Periodic Table Groups and Properties

Periodic Table Groups

• Very unreactive due to full valence shell

• Odorless, colorless, gases

1

• Extremely reactive; not found in pure form in nature

•Silverly, soft• form strong bases in water

• less reactive than alkali, but still not found in pure form

• also form strong bases in water

Transition Metals

• typical metallic properties• form colorful ions

• shiny metals• similar reactivity to Group 2• filling 4f sublevel

• mainly synthetic (created in a lab)• all radioactive

• very reactive• volatile (exist as gases)

1

Properties of Metals

1. shiny (luster)2. conductors of heat and electricity3. reactive with acids4. ductile

– can be stretched into a wire

5. malleable – can be hammered or rolled into sheets

6. forms positive ions (by losing e-)

Properties of Nonmetals

1. dull and brittle2. poor conductors of heat and

electricity3. does not react with acids4. usually gases at room temp.5. forms negative ions (by gaining e-)

What are properties of Metalloids??

•In the middle!•Metalloids have properties of BOTH!! (metals and nonmetals)

Periodic Trends

PERIODIC LAW

When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic (repeating) pattern.

patterns on the periodic table are called periodic trends

Atomic Radius

half the distance from center-center of 2 like atoms

Atomic Radii DOWN a Group

↓As you go down there are more energy levels, the atom size gets larger

↓There are more electrons between the nucleus and the outermost energy level which increases the shielding effect

Shielding Effect

• reduction of attraction between positive nucleus and outermost electrons

•outer electrons are not held tight and can move away

Na

Atomic Radius: down group

P

PP

X

X

X

P

X

P

X

P

X

P

PP

P

P

X

X

X

X

X

XP

K

Atomic Radius: down group

P

PP

X

X

X

P

X

P

X

P

X

P

PP

P

P

X

X

X

X

X

PX

X

X

X

X

X

X

X

X

Atomic Radii DOWN a Group

↓DOWN THE GROUP ATOMIC RADIUS

INCREASES

more energy levels, the larger the size of the atom

Atomic Radii ACROSS a Period

→ Each atom gains one proton and one electron in the same energy level

→Each added electron is the same distance from the nucleus

→The positive charge increases and exerts a greater force on the electrons pulling them closer to the nucleus

REMEMBER!

PROTONSare bigger and stronger!

electrons are smaller and weaker!P

+ + - -

e

Ask yourself, how effective are the positive protons pulling in the electrons?

Atomic Radii ACROSS a Period

Effective nuclear charge: “positive charge” felt by an electron.

Within a period, every time a proton is added, the effective nuclear charge increases… so the radius decreases

Atomic Radius: across period

P

PP

X

X

X

P

X

P

X

P

X

P

PP

P

P

X

X

X

X

X

Atomic Radii ACROSS a Period

→ACROSS THE PERIOD ATOMIC RADIUS

DECREASES

greater effective nuclear charge (more protons), greater pull on the electrons, smaller radius

Ionic Radii

half the distance from center-center of 2 like ions

Ionic Radius DOWN a Group

↓As you go down a group another energy level is added, increasing the size of the atom.

(just like the atomic radius)

Ionic Radius DOWN the Group

↓DOWN THE GROUP IONIC RADIUS

INCREASES

more energy levels, increase in atom size

Ionic Radius ACROSS the Period

Cation: positive ion formed from losing an electron

→ A cation is always smaller than the original atom

→The more electrons lost the more protons available to attract a smaller number of electrons.

Na +

Ionic Radius

P

PP

XP

X

X

PP

P

PP

P

P

X

X

X

X

X

X

X

X

XP

Ionic Radius ACROSS the Period→ACROSS THE PERIOD IONIC RADIUS

DECREASES

greater effective nuclear charge, less electrons, the shorter the radius

Ionic Radius ACROSS the Period

Anion: negative ion formed from gaining an electron

→ A anion is always larger than the original atom

→The more electrons gained, the less protons available to attract a larger number of electrons.

F

Ionic Radius

P

PP

XP

X

X

PP

P

PP

P

P

X

X

X

X

X

X

X

X

P

-

Ionic Radius ACROSS the Period

→ACROSS THE PERIOD IONIC RADIUS

DECREASES

As electrons are added the atom gets larger from right to left,

General trend from left to right is decreasing

Ionic Radii

amount of energy needed to remove an electron from an atom

Ionization Energy

X X+ + e-

X X2++ e-

X X3++ e-

I1 first ionization energy

I2 second ionization energy

I3 third ionization energy

I1 < I2 < I3

Multiple Ionization Energies

Ionization Energy DOWN a Group

↓As you go down a group atoms become larger

↓The more electrons in an atom between the nucleus and valence shell, the greater the shielding effect

Ionization Energy DOWN a Group

↓DOWN THE GROUP IONIZATION ENERGY

DECREASES

greater distance from the nucleus, greater shielding effect

less energy needed to remove electron

Ionization Energy ACROSS a Period

→As atomic radius decreases there is a greater attraction between protons and electrons. (effective nuclear charge)

→The stronger the attraction, the more energy needed to remove an electron.

Ionization Energy ACROSS a Period

→ACROSS THE PERIOD IONIZATION ENERGY

INCREASES

greater the effective nuclear charge,more energy required to remove electron

Electronegativity

It is a “tug of war” between the two atoms of a bond

H F :

::

Which is the more electronegative element?

.

..

ability of an atom to attract electrons

Electronegativity DOWN the Group

↓The farther away from the nucleus, the greater the shielding effect

↓The larger the atom, the less likely it is to accept more electrons.

Electronegativity DOWN the Group

↓DOWN THE GROUP ELECTRONEGATIVITY

DECREASES

farther the distance from the nucleus, lower ability to attract electrons

Electronegativity ACROSS the Period

→As you go across a period atomic radius decreases because there is a greater effective nuclear charge

→Metals do not attract electrons. →Non-metals do attract electrons.

Electronegativity ACROSS the Period

→ACROSS THE PERIOD ELECTRONEGATIVITY

INCREASES

greater effective nuclear charge, greater ability to attract electrons

the energy change that occurs when an electron is added to an atom to form an

anion.

Increases with ability to attract and hold an electron (electronegativity)

Electron Affinity

Electron Affinity DOWN the Group

↓The larger the atom the more difficult to accept electrons

Electron Affinity DOWN the Group

↓DOWN THE GROUP ELECTRON AFFINITY

DECREASES

farther the distance from the nucleus,does not want to gain electrons

Electron Affinity ACROSS the Period

→As effective nuclear charge gets stronger, it is easier to attract an electron.

Electron Affinity ACROSS the Period

→ACROSS THE PERIOD ELECTRON AFFINITY

INCREASESgreater effective nuclear charge,

easily forms anions

Other TrendsReactivity of Metals Video 1Reactivity of Metals Video 2

Incr

easi

ng r

eact

ivity

METAL REACTIVITY

Incr

easi

ng r

eact

ivity

NONMETAL REACTIVITY