ObjectivesObjectives

Describe how Mendeleev arranged the elements in the periodic table

Explain how the predictions Mendeleev made and the discovery on new elements demonstrated the usefulness of his periodic table

History on the Organization of History on the Organization of ElementsElements

Antoine Lavoiser

- organized known elements (very few) into metals, non metals, gases, and earths

Dmitri Mendeleev

- organization based on a popular card game solitaire

- each card had the elements name, mass, and properties

- lined up the cards in order of increasing mass, found a pattern

- elements with similar properties were in the same column

Mendeleev Mendeleev

Predictions- could not make a complete table, only had 63 elements leaving many spaces between elements- used properties of other elements to predict undiscovered elements properties

MendeleevMendeleev Evidence

- named some of the missing elements, and predicted some of their properties

- as elements were found scientists were able to verify properties and even explain chemical behaviors of elements in groups

Periodic LawPeriodic Law- Mendeleev’s periodic table was completed before

the discovery of protons.

- by looking at certain trends, among the elements a new organization was created

Periodic Law

- pattern of repeating properties displayed by elements in the periodic table

SO….the periodic table is now arranged by atomic number instead of atomic mass

ObjectivesObjectives Describe the arrangement of elements in the

modern periodic table Understand the trends that established the

modern periodic table Locate periods and groups in the period table

Valence ElectronsValence Electrons Definition

- an electron that is in the highest occupied energy level of an atom

- determine the properties of elements

Lewis Dot StructuresLewis Dot Structures- electron dot diagram, where each dot represents a

valence electron

ex.

Practice Problems

Br K

Be Al

IonsIons Definition

- an atom or group of atoms that has a positive or negative charge

ex. Cl-, Ca2+

Formation of Ions

- atom gains or loses electrons (protons electrons)

- atom is no longer neutral

- become a cation or an anion

Ions Cont.Ions Cont.

- cation (+): lost electrons

- now name of atom + ion : sodium ion

- anion (-): gained electrons

- now ends in ide: Chloride

Organizing the Elements Cont.Organizing the Elements Cont. Atomic Radii:

- half the distance between the nuclei of the same atoms bonded together

Atomic RadiusAtomic Radius

Trend #1Trend #1Atoms get larger going down a group

Hydrogen (1s1)

Lithium (1s2 2s1)

Sodium (1s2 2s2 2p6 3s1)

Shielding EffectShielding Effect

Atomic RadiusAtomic RadiusTrend #2Trend #2

Shrinking EffectShrinking Effect

5p+ 6p+ 7p+

1s2 2s2 2p1

1s2 2s2 2p2

1s2 2s2 2p3

Atomic Radii of Representative Elements (nm)Atomic Radii of Representative Elements (nm)1A 2A 3A 4A 5A 6A 7A

K

Rb

Cs

Be

Mg

Ca

Sr

Ba

Al

Ga

In

Tl

Sn

Pb Bi Po At

Sb Te

Ge

Si

B

As

C N

P S Cl

Se Br

I

LiF

Na

O

Ato m

ic Rad iu s in cr ea se s

Atomic Radius increases

HLiNa

K

Fr

F

At

Atomic RadiusAtomic Radius

Trends of the Atomic RadiiTrends of the Atomic Radii

- at certain intervals, atomic radii is dramatically greater than that of the previous element

Trends of the Atomic RadiiTrends of the Atomic Radii

Organizing the Elements Cont.Organizing the Elements Cont. Ionization energy:

- amount of energy required to pull an electron away from an atom to form a positively charged ion

- generally increases with increasing atomic number

- at some points, when atomic number increases there is a dramatic decrease

ex. Li, Na, K, Rb, Cs, Fr

Ionization EnergyIonization Energy

Energy needed to remove one of atom’s electrons from its outermost shell

A + E A+ + e-

Reflection of how strongly an atom holds onto its outermost electron.

Atoms with high ionization energies hold onto Atoms with high ionization energies hold onto their electrons very tightly.their electrons very tightly.

Atoms with low ionization energies are more likely Atoms with low ionization energies are more likely to lose one or more of their outermost electron.to lose one or more of their outermost electron.

Ioni

zatio

n en

ergy

incr

ease

s

Ionization energy increases

HLiNa

K

Fr

F

At

Ionization EnergyIonization Energy

Trends of Ionization EnergyTrends of Ionization Energy

Trends of Ionization EnergyTrends of Ionization Energy

Electron AffinityElectron Affinity

A + e- A- + E

Measure of an atom’s attraction, or affinity, for an extra electron.

Energy released when an atom gains an electron to form a negative ion/anion.

Electron affinity increases within a period from left to right. As one goes down a group, electron affinity decreases.

ElectronegativityElectronegativity

Ability of an atom to attract electrons in a chemical bond.

Ele

ctro

nega

tivity

incr

ease

s

Electronegativity increases

HLiNa

K

Fr

F

At

Ionic RadiusIonic Radius

Anion (negative ion), its size increases, since the nuclear charge remains the same but the repulsion resulting from the additional electron(s) enlarges the domain of the electron cloud.

Ionic RadiusIonic Radius

Cation (positive ion) smaller than neutral atom, since removing one or more electrons reduces electron-electron repulsion but the nuclear charge remains the same, so the electron cloud shrinks.

From top to bottom of a periodic group both the atomic radius and the ionic radius increases.

Ionic RadiusIonic Radius

+Li F Li+ F--

Changes in size when Li reacts with F to form LiF

Ionic Radii of Representative Elements (nm)Ionic Radii of Representative Elements (nm)1A 2A 3A 4A 5A 6A 7A

Sb Te

N

P

As

PoBi

S

Br

I

At

Rb

Cs Ba Tl

Sr

K

Na

F

Se

O

ClMg Al

Ca Ga

In

BBe

Li

Si

Ge

Sn

Pb

C

Organizing the Elements Cont.Organizing the Elements Cont.

* Because other properties of the elements follow the same pattern, it is natural to group the elements according to these intervals

Organizing the Elements Cont.Organizing the Elements Cont.- each row is commonly referred to as a period

- there are 7 periods

- each period is placed on top of each other, giving rise to columns, known as a group

Organizing the Elements Cont.Organizing the Elements Cont.

- slight modifications of He; nothing in common with the 2nd elements of the other periods

- Helium moves right until it is aligned with other similar elements such as Ne, Ar, and other noble gasses

- 2nd period we slide B through Ne

- 3rd period we slide Al through Ar

Results of OrganizationResults of Organization 7 periods (Across)

- Atomic Radius decreases - Ionization energy increase - Electron Affinity increases

18 Groups (Down)- Atomic Radius increases- Ionization energy decreases- Electron affinity decreases- Elements have similar chemical and physical properties- # of valence electrons are the same

Organizing the Elements Cont.Organizing the Elements Cont.

ObjectivesObjectives Identify general properties of the metals, non

metals, and metalloids. Describe how properties of elements change

across a period in the periodic table

How are Elements Classified?How are Elements Classified? Three Regions

- metals, and nonmetals, and metalloids

MetalsMetals Metals

- include group 1 -12 and some elements from 13 -16

- most known elements

- good conductors of electricity/heat

- solid at room temperature, except mercury

ex. Na, Ag, Pb

Non MetalsNon Metals Definition

- elements that are poor conductors of electricity/heat

- low boiling points, SO…most are gases at room temperature

- varying chemical properties

ex. He, F, P

MetalloidsMetalloids Definition

- elements with properties that fall between those of metals and non metals

- chemical properties will vary, usually most like the region they are closer to

ex. As: closer to non metal most of it’s property will resemble that

Families of the Periodic TableFamilies of the Periodic Table Families/Groups

Alkali metalsAlkali Earth metalsBoron FamilyCarbon FamilyNitrogen FamilyOxygenTransition MetalsHalogensNoble Gases

Alkali MetalsAlkali Metals Definition

- highly reactive metallic elements in group 1

- react with water to form hydrogen and alkaline solutions; burn in air

- al-quili means wood ashes

- term dates back to ancient times; people discovered that wood ashes mix with water to produce slippery solutions that can remove grease

- one outer electron, by losing this electron they become a cation, and become stable

Alkali Metals Cont.Alkali Metals Cont.

- soft metals; can be cut with a knife

- shiny, but dull quickly due to oxygen and water in air

- good conductors

- gaseous states at high temperatures become plasmas

ex. Na, Cs, Rb

Alkali-Earth MetalsAlkali-Earth Metals Definition

- group 2 elements

- comes from idea of “Earth”, materials unable to light on fire

- reactive metallic elements with two electrons in the outermost energy level

- harder, denser, stronger and have higher melting points, lower reactivity than alkali

ex. Be, Ca, Mg

Transition Metals Transition Metals Lanthanides

- shiny, metallic transition metals (58 – 71) in which electrons are added to 4f orbitals- located at the bottom of the periodic table for convenience

Actinides- shiny metallic transition metals (90 – 103) in

which electrons are added to 5f orbitals- located at the bottom of the periodic table for

convenience- radioactive

HalogensHalogens

Definition

- nonmetallic elements in group 17, that have 7 electrons in the outer most energy level and combines with many metals to form salts

- term comes from Greek means “salt former”

Salt: a compound composed of positive and negative ions arranged in a regular 3D pattern

- most reactive group of nonmetals

- varying physical properties, similar chemical properties

Noble GasNoble Gas Definition

- elements in group 18 that are characterized by low reactivity- term comes from noble people, did not associate with anyone other then their kind- characterized by an octet of electrons in the outermost energy level; (happy)

- exception of helium- very stable, (unreactive)- colorless, odorless- practical applications: balloons, illumination

HydrogenHydrogen- most common element in the universe

- behaves unlike any other element due to its structure of 1 p 1 e

- react with numerous elements

- component of all hydrocarbons, and molecules that are essential to life; fats, proteins, carbohydrates

- practical uses

ex. ammonia, fertilizers

MetallicityMetallicity

Ability of an atom to lose an electron

TREND:

Increases from top to bottom

Decreases from left to right

Ele

ctro

nega

tivity

incr

ease

s

Ele

ctro

n af

fini

ty in

crea

ses

Electronegativity increases

HLiNa

K

Fr

F

At

Ioni

zatio

n en

ergy

incr

ease

s

Ionization energy increases

Electron Affinity increases

Summary of Periodic TrendsSummary of Periodic Trends

Ato m

ic Rad iu s in cr ea se s/ io n ic si ze

Metallicity inreasesAtomic Radius increases/ Ionic size

Me ta lli cit y in cr ea se s

Challenge Challenge

1. Arrange the following groups of atoms in order of decreasing atomic size:

a. B, Al, Gab. Sn, Sb, Tec. Cd, Si, Gad. As, P, Cl

Answers Answers

1. a. Ga, Al, B

b. Sn, Sb, Te

c. Cd, Ga, Si

d. As, P, Cl

e. Cl, O, F

ChallengeChallenge

2. For each of the following pairs, predict which element has (1) the larger radius, and (2) the larger ionization energy:

a. Na & Clb. C & Oc. Li & Rbd. As & Fe. Ne & Xef. N & Sbg. Sr & Sih. Fe & Br

AnswersAnswers

a. (1) Na, (2) Cl

b. (1) C, (2) O

c. (1) Rb, (2) Li

d. (1) As, (2) F

e. (1) Xe, (2) Ne

f. (1) Sb, (2) N

g. (1) Sr, (2) Si

h. (1) Fe, (2) Br

Challenge Challenge

3. List the following ions in order of increasing ionic radius: N3-, Na+, F-, Mg2+, O2-

4. Indicate which one of the two species in each of the following pairs is smaller:

a. Cl or Cl-

b. Na or Na+

c. O2- or S2-

d. Mg2+ or Al3+

e. Au+ or Au3+