The Periodic Table

contentcontent i. Dimitri Mendeleev's periodic table ii. The modern periodic table iii. Families of the periodic table iv. Periodic trendsv. Ionization energyvi. Ionsvii. Valence electronsviii. Electronegativity ix. Lewis’s Octet rulex. Credit

i. Dimitri Mendeleev's periodic table ii. The modern periodic table iii. Families of the periodic table iv. Periodic trendsv. Ionization energyvi. Ionsvii. Valence electronsviii. Electronegativity ix. Lewis’s Octet rulex. Credit

Dmitri Mendeleev: Father of the Table

HOW HIS WORKED…

• Put elements in rows by increasing atomic mass.

• Put elements in columns by the way they reacted.

SOME PROBLEMS…• He left blank spaces

for what he said were undiscovered elements.

• He broke the pattern of increasing atomic mass to keep similar reacting elements together.

The Current Periodic Table

• Now the elements are put in rows by

increasing ATOMIC NUMBER

• The horizontal rows are called periods and are labeled from 1 to 7.

• The vertical columns are called groups are labeled from 1 to 18.

Families on the Periodic Table• Columns are also grouped into

families.• Families may be one column, or

several columns put together.• Families have names rather than

numbers.

HydrogenHydrogen

Hydrogen belongs Hydrogen belongs to a family of its to a family of its own.own.

Hydrogen is a Hydrogen is a diatomic, reactive diatomic, reactive gas.gas.

Alkali MetalsAlkali Metals

11stst column on the column on the periodic table (Group periodic table (Group 1) not including 1) not including hydrogen. hydrogen.

Very reactive metals, Very reactive metals, always combined with always combined with something else in something else in nature (like in salt).nature (like in salt).

Alkaline Earth Metals

Second column on the periodic table. (Group 2)

Reactive metals that are always combined with nonmetals in nature.

Several of these elements are important mineral nutrients (such as Mg and Ca)

Metals vs. NonmetalsMetals vs. Nonmetals

Metals are shiny, good conductors of heat Metals are shiny, good conductors of heat and electricity, malleable, ductile, and form and electricity, malleable, ductile, and form cations (positive ions, loss of electrons) cations (positive ions, loss of electrons) during chemical change.during chemical change.

Nonmetals are not shiny. They are poor Nonmetals are not shiny. They are poor conductors, brittle. They frequently form conductors, brittle. They frequently form anions (negative, gain of electrons) in anions (negative, gain of electrons) in chemical changes.chemical changes.

Transition MetalsTransition Metals

• Elements in groups 3-12Elements in groups 3-12

• Less reactive harder Less reactive harder metalsmetals

• Includes metals used in Includes metals used in jewelry and construction.jewelry and construction.

MetalloidsMetalloids

Metalloids have some characteristics of Metalloids have some characteristics of both metals and nonmetals. They are B, both metals and nonmetals. They are B, Si, Ge, As, Sb, Te, Po, At.Si, Ge, As, Sb, Te, Po, At.

HalogensHalogens

Elements in group 17Elements in group 17 Very reactive, Very reactive,

volatile, diatomic, volatile, diatomic, nonmetalsnonmetals

Always found Always found combined with other combined with other element in nature .element in nature . (CHLORINE)

The Noble GasesThe Noble Gases

AKA Inert GasesAKA Inert GasesElements in Elements in

group 18group 18VERY unreactive, VERY unreactive,

monatomic monatomic gasesgases

Have a full Have a full valence shell.valence shell.

Periodic Trends

Moving left to right across a period, atomic radius usually decreases. This occurs because each successive element has an added proton and electron which causes the electron to be drawn closer to the nucleus.

This decrease in atomic radius also causes the ionization energy to increase when moving from left to right across a period. The more tightly bound an element is, the more energy is required to remove an electron.

Similarly, electronegativity will increase in the same manner as ionization energy because of the amount of pull that is exerted on the electrons by the nucleus.

Summary of Periodic Trends

Ionization energyIonization energy

Energy required to overcome the attraction of the nuclear charge and to remove an electron from a

gaseous atom.

Energy required to overcome the attraction of the nuclear charge and to remove an electron from a

gaseous atom.

Ions

• + positive ions - cations - always smaller

than the neutral atom from which they form because loss of outer-shell electrons result in increased attraction by nucleus for the fewer remaining electrons.

negative ions - anions - always larger than the neutral atom because effective nuclear attraction is less for increased number of electrons

Group trends v.s

period trends

Ionic radii increase as moving down each group

Gradual decrease in size for both cations and anions as moving from left to right

electronegativity

The tendency for atoms of the element to attract electrons when they are chemically combined with atoms of another element

They are calculated and expressed in arbitrary units called Paulings

Pauling electronegativity scale

• Noble gases do not form any compund so omitted in the scale

• Electronegativiy of representative elments(Group A elements) increases as moving from left to right

• Metallic elements= low• Non-metallic elements= high• Most electronegative: Fluorine- 4.0• Least electronegative: Cesium- 0.7• Elctronegativity values help predict type

of bonding between atoms in compounds.

Valence electrons

Electrons in the highest occupied enegy level of an element’s atoms

The number of valence electrons largely determines the chemical properties of an element

Therefore: elements within each group behave similarly because they have the same number of V.e-

Valence electrons

• The number of valence electrons is the same as the group number of the element. (eg.Gr 1A elements has 1 V.e-)

• EXCEPTION: GR 0 (noble gases)- Helium has 2 V.e- and all others have 8.

• V.e- are usually the only electrons used in chemical bonding so only V.e- are shown in electron dot structures.

Octet ruleOctet rule

Gilbert Lewis, 1916 In forming compounds, atoms tend to

achieve the electron configuration of a noble gas (ns2np6)

Atoms of metallic elements tend to lose V.e-, leaving complete octet in next lowest energy level

Atoms of some non-metallic elements tend to gain e- or to share e- with another non-metallic element to achieve a complete octet.

Gilbert Lewis, 1916 In forming compounds, atoms tend to

achieve the electron configuration of a noble gas (ns2np6)

Atoms of metallic elements tend to lose V.e-, leaving complete octet in next lowest energy level

Atoms of some non-metallic elements tend to gain e- or to share e- with another non-metallic element to achieve a complete octet.

CreditsCredits

Powerpoint presentation designed by:

Victoria Gotay and Mengyi Xu

Content sources:

ChemistryChemistry, fifth edition, Addison-Wesley publications

Images and graphs souces:www.webelements.comwww.wsd1.orgwww.iamanangelchaser.com

Powerpoint presentation designed by:

Victoria Gotay and Mengyi Xu

Content sources:

ChemistryChemistry, fifth edition, Addison-Wesley publications

Images and graphs souces:www.webelements.comwww.wsd1.orgwww.iamanangelchaser.com

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