Chapter 14: Chemical Periodicity

The Periodic TableMendeleev website

• Russian chemist Dmitri Mendeleev is credited with making the basis for the periodic table that is still used today.

• Periodic table shows atomic number, atomic mass, element name, element symbol, and amount of electrons in each energy level.

Metals Non-Metals

*Lose Electrons *Gain electrons

*Conductors of electricity *Poor conductors of electricity

*Conductors of heat * Poor conductors of heat

*Luster *Lack luster

*Malleable *Non-malleable

Alloys• Alloys-mixtures

composed of two or more elements at least one of which is a metal

• Alloys are prepared by melting the mixture of the ingredients and then cooling the mixture

• Brass is an alloy of copper and zinc

• Bronze is an alloy of 7 parts copper and one part tin

• Steel is an alloy of iron and carbon. It is corrosion resistant ductile, hard and tough.

Alloy Properties

• Shows an alloy mixture. It is NOT a compound but a physical mixing of a metal plus at least one other material (shown by red circle, it can be another metal eg Ni, a non-metal eg C or a compound of carbon or manganese, and it can be bigger or smaller than iron atoms). Many alloys are produced to give a stronger metal. The presence of the other atoms (smaller or bigger) disrupts the symmetry of the layers and reduces the 'slip ability' of one layer next to another. The result is a stronger harder less malleable metal.

Alloy Properties

The Noble Gases

• The noble gases include helium, neon, argon, and krypton.

• These are elements in which the outermost s and p sublevels are filled.

• Also called inert gases because they do not participate in many chemical reactions.

The Representative Elements

• The representative elements outermost s or p sublevels are only partially filled.

• Blocks S and P in the diagram.• There are three groups of representative

elements: the alkali metals, the alkaline earth metals, and the halogens.

The Transition Metals

• The transition metals are metallic elements in which the outermost s sublevel and nearby d sublevel contain electrons.

• Such metals include iron, copper, gold, silver, nickel, zinc and many others.

The Inner Transition Metals

• The inner transition metals are metallic elements in which the outermost s sublevel and nearby f sublevel generally contain electrons.

• Such metals include uranium, plutonium, actinium, and many others.

Websites of Metals

• History of Metals• Transition metal info.

Electron Configuration• Noble Gases: • Helium: 1s2

• Neon: 1s22s22p6

• Argon: 1s22s22p63s23p6

• Krypton: 1s22s22p63s23p63d104s24p6

Electron Configurations

• The electron configuration is the arrangement of electrons around the nucleus of an atom in its ground state.

• Here are some examples of electron configurations:

Fe: 1s22s22p63s23p64s23d6 Mg: 1s22s22p63s2

Ionization energy

• The energy needed to remove an electron from an atom.

The energy required to remove an electron from a gaseous atom.

Moving left to right on the periodic table, ionization energy increases.

Moving down a group in the periodic table, ionization energy decreases.

Moving left to right on the periodic table, electron affinity increases.

Element Group 1st 2nd 3rd 4th 5th 6th

A 1086 2352 4621 6223 37832 47279

A 520 7298 11815

A 899 1752 14849 21007 25114

A 1312

Ionization Energy• The energy required to overcome the

attraction of the nuclear charge and remove an electron from a gaseous atom.

• Removing one electron results in the formation of a positive ion, 1+ charge.

Electronegativity

• The ability of an atom to attract electrons when forming bonds.

Electronegativity Values-use to determine bond type

• Electronegativity and Shielding Effect• __________related. This means that when one repels an

electron, the other attracts an electron.• Shielding Effect is ____________related to Ionization Energy• Electron Affinity is __________related to shielding effect• Ionization energy is __________related to shielding effect• Electron Affinity (attraction for electrons)

• Fluorine has the most electronegativity

• Lithium has the least amount of electronegativity

• Group 7 on the periodic table wants to gain one electron. That group has the highest electronegativity.

Shielding Effect

• Electron levels act like shields.

• They shield all other electrons from the nucleus

• Result : larger elements lose electrons easier

Shielding Effect

Atomic Radius / Ionic Radius

• Atomic Radius - The size of an atom before reacting

• Ionic Radius -The size of an atom after reacting

• (Reacting refers to the loss or gain of an electron)

Li

152

60

Li+

e -

Atomic vs. Ionic Radii

•

Atomic/Ionic Radius• Atomic Radius: the size of an atom

before reacting.• Ionic Radius: the size of an atom after

reacting.

Periodic Trends refer to the varying properties that are relative to your direction going across and down the periodic table.

…These varying properties include...

Atomic RadiusIonic SizeIonization Energy

Nuclear ChargeShielding EffectElectronegativity

Periodic TableNuc le

a r c

h ar g

e i n

crea

s es

Shie

l di n

g in

c rea

ses

Atom

ic R a

d ius

inc r

e ase

sIo

nic

s ize

inc r

ease

sIo

niza

t ion

E ner

gy d

ecr e

a se s

Elec

t rone

g at iv

ity d

e cre

a ses

Nuclear charge increasesShielding is constantAtomic Radius decreasesIonization Energy increasesElectronegativity increases

The End