The Periodic TableUnit 3/Chapters 3 & 8 Notes

Chemistry CPA

Unit Objectives: • To describe the contribution of the structure of the periodic table by scientists such as

Dobereiner, Mendeleev, and Mosley• To describe the information given in an element square on the periodic table• To know the difference (in structure and properties) between families/groups and periods• To be able to distinguish between metals, nonmetals and metalloids and know their

general location on the periodic table• To describe the general physical and chemical properties of metals and nonmetals• To be able to name and identify the properties of the following families: Alkali metals,

alkaline earth metals, transition metals, boron family, carbon family, nitrogen family, oxygen family, halogens and noble gases

• To be able to analyze the major trends on the periodic table: atomic radius, ionization energy, electronegativity, and electron affinity, and reactivity

The History of the Periodic Table

Dobereiner’s Triads• In 1829, Johann Wolfgang Dobereiner, a German scientist, was the first to classify elements into groups based on John Dalton's postulates.• He grouped the elements with similar

chemical properties into clusters of three called 'Triads'. • The distinctive feature of a triad was

the atomic mass of the middle element.• When elements were arranged in

order of their increasing atomic mass, the atomic mass of the middle element was approximately the average of the other two elements of the triad.

Mendeleev

• In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table. • He grouped elements according to

their atomic mass, and as he did, he found that the families had similar chemical properties. • Blank spaces were left open to add

the new elements he predicted would occur.

Mendeleev’s Table

Mosely

• Later, Henri Moseley (England, 1887-1915) established that each elements has a unique atomic number, which is how the current periodic table is organized.

What’s in a square?• Different periodic tables can

include various bits of information, but usually:• atomic number• symbol• atomic mass• number of valence electrons• state of matter at room

temperature.

Organization of the periodic table – Families/Groups (columns)(notes)

• The vertical columns of the table are called groups or families. Element in the same group have similar but not identical characteristics• Numbered from 1 to 18. • Elements in the same group have the same number of outer shell electrons, and hence similar chemical properties.

Organization of the periodic table – Periods (columns)• The horizontal rows of the table are called periods.• Numbered from 1 to 7. • Each contains elements with electrons in the sameouter shell. • Elements do not have similar properties in the periods like Families do.

More on Families and Periods…Families/Groups: • Columns of elements are called groups

or families. • Elements in each family have similar

but not identical properties.• For example, lithium (Li), sodium (Na),

potassium (K), and other members of family IA are all soft, white, shiny metals.• All elements in a family have the same

number of valence electrons.

Periods:• Each horizontal row of elements is

called a period.• The elements in a period are not alike

in properties.• In fact, the properties change greatly

across even given row.• The first element in a period is always

an extremely active solid. The last element in a period, is always an inactive gas.

Types of elements• There are three main types of elements:

metals, non metals and metalloids• 1. Metals appear on the left hand side of

the zig zag line that separates the periodic table• 2. Non metals appear on the right hand

side of the zig zag line that separates the periodic table• 3. Elements on either side of the zigzag

line have properties of both metals and non-metals. These elements are called metalloids.

Properties of Metals• Most elements are metals. 88

elements to the left of the stairstep line are metals or metal like elements.• Left side of the periodic table• Positive valencies

Physical Properties of Metals• Luster (shininess) • Good conductors of heat and

electricity • High density (heavy for their

size) • High melting point • Ductile (most metals can be

drawn out into thin wires) • Malleable (most metals can be

hammered into thin sheets)

Chemical Properties of Metals• Easily lose electrons • Corrode easily. Corrosion is a

gradual wearing away. (Example: silver tarnishing and iron rusting)

Properties of Nonmetals• Nonmetals are found to the right

of the stairstep line. Their characteristics are opposite those of metals.

Sulfur

Physical Properties of non-Metals• No luster (dull appearance) • Poor conductor of heat and electricity • Brittle (breaks easily) • Not ductile • Not malleable • Low density • Low melting point

Chemical Properties of Nonmetals• Tend to gain electrons • Since metals tend to lose electrons and nonmetals tend to gain

electrons, metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds. When two or more nonmetals bond with each other, they form a covalent compound.

Properties of Metalloids• Metalloids (metal-like) have

properties of both metals and non-metals.• They are solids that can be shiny

or dull.• They conduct heat and

electricity better than non-metals but not as well as metals.• They are ductile and malleable.

Hydrogen

• The hydrogen square sits atop Family AI, but it is not a member of that family. Hydrogen is in a class of its own.• It’s a gas at room temperature.• It has one proton and one electron in its one

and only energy level.• Hydrogen only needs 2 electrons to fill up its

valence shell.

Alkali Metals

• The alkali family is found in the first column of the periodic table.• Atoms of the alkali metals have

a single electron in their outermost level, in other words, 1 valence electron.• They are shiny, have the

consistency of clay, and are easily cut with a knife.

Alkali Metals

• They are the most reactive metals.• They react violently with water.• Alkali metals are never found as

free elements in nature. They are always bonded with another element.

What does it mean to be reactive?• We will be describing elements according to their reactivity. • Elements that are reactive bond easily with other elements to make compounds.• Some elements are only found in nature bonded with other elements. • What makes an element reactive?

• An incomplete valence electron level.• All atoms (except hydrogen) want to have 8 electrons in their very outermost energy level

(This is called the rule of octet.)• Atoms bond until this level is complete. Atoms with few valence electrons lose them during

bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.

Reactivity of Metals• http://www.youtube.com/watch?v=V2TimLxskZw (Magnesium in water)

• http://www.youtube.com/watch?v=nSgIr1Wba_g&feature=related (Calcium in water)

• Group One (Alkaline Metals) are more reactive than Group 2 (Alkaline Earths)• As you go down a group metals become more reactive• This happens because as you go down a group atoms

get larger and metals tend to donate electrons in reactions.

Reactivity of Non metals• Look at table 3.3 to see which Halogen is most

reactive• Reactivity decreases down the group• Why? Think about atomic properties• Non metals tend to form negative ions (they gain

electrons from other atoms)• Electronegativity or love of electrons is strongest with

Fluorine and decreases down the group.

Alkaline Earth Metals

• They are never found uncombined in nature.• They have two valence electrons.• Alkaline earth metals include magnesium and calcium, among

others.

Transition Metals

• Transition Elements include those elements in the B families.• These are the metals you are

probably most familiar: copper, tin, zinc, iron, nickel, gold, and silver.• They are good conductors of heat

and electricity.

Transition Metals

• The compounds of transition metals are usually brightly colored and are often used to color paints.• Transition elements have 1 or 2 valence electrons, which they lose when they

form bonds with other atoms. Some transition elements can lose electrons in their next-to-outermost level.

Transition Elements• Transition elements have properties similar to one another and to

other metals, but their properties do not fit in with those of any other family. • Many transition metals combine chemically with oxygen to form

compounds called oxides.

Boron Family

• The Boron Family is named after the first element in the family.• Atoms in this family have 3

valence electrons.• This family includes a metalloid

(boron), and the rest are metals.• This family includes the most

abundant metal in the earth’s crust (aluminum).

Carbon Family

• Atoms of this family have 4 valence electrons.• This family includes a non-metal

(carbon), metalloids, and metals.• The element carbon is called the

“basis of life.” There is an entire branch of chemistry devoted to carbon compounds called organic chemistry.

Nitrogen Family• The nitrogen family is named

after the element that makes up 78% of our atmosphere.• This family includes non-metals,

metalloids, and metals.• Atoms in the nitrogen family have

5 valence electrons. They tend to share electrons when they bond.• Other elements in this family are

phosphorus, arsenic, antimony, and bismuth.

Oxygen Family

• Atoms of this family have 6 valence electrons.• Most elements in this family

share electrons when forming compounds.• Oxygen is the most abundant

element in the earth’s crust. It is extremely active and combines with almost all elements.

Halogen Family

• The elements in this family are fluorine, chlorine, bromine, iodine, and astatine.• Halogens have 7 valence electrons,

which explains why they are the most active non-metals. They are never found free in nature.• Halogen atoms only need to gain 1

electron to fill their outermost energy level.• They react with alkali metals to form

salts.

Noble Gases

• Noble Gases are colorless gases that are extremely un-reactive. • One important property of the noble gases is their inactivity. They are inactive because their outermost energy

level is full. • Because they do not readily combine with other elements to form compounds, the noble gases are called inert.• The family of noble gases includes helium, neon, argon, krypton, xenon, and radon. • All the noble gases are found in small amounts in the earth's atmosphere.

Rare Earth Elements

• The thirty rare earth elements are composed of the lanthanide and actinide series.• One element of the

lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.

Periodic Trends• Many properties of atoms depend on the strength

of attraction between the outer shell electrons and the nucleus

• This attraction will depend on:1. The positive charge that attracts the other shell

electrons2. The distance of electrons from the nucleus

Four Periodic Trends1. Atomic Radius2. Ionization Energy3. Electronegativity4. Electron Affinity

Atomic RadiusWhat is it? • Diameter of atom What happens down a group?• Increases• since there is an increase in the number of shells.What happens across a period?• Decreases• since there is an increase in core charge, the outer shell electrons are

attracted closer to the nucleus (it’s the same shell but there are more electrons in the shell as you move across the period)

Atomic Radius decreases across a period

Atomic Radius increases down a family/group

Ionization Energy• What is it?• Amount of energy required toremove the highest energy electron from an atom. (or steal one electron)• What happens down a group?• Decreases; since the size of the atom is increasing, the attraction is weaker

between the outer shell electrons and the nucleus. Therefore electrons are easier to remove. • What happens across a period?• Increases; since there is an increase in core charge, the attraction is greater

between the outer shell electrons and the nucleus. Therefore electrons are harder to remove.

ee ee e e

Ionization Energy• In other words…• If its easy to steal a electron, it has low ionization

energy• If its hard to steal an electron, it has a high ionization

energy • The smaller the atom, the harder to steal an electron• The larger the atom the easier it is to steal an electron

Ionization Energy

Electronegativity• What is it?• Measure of the ability of an atom to attract an electron towards itself

or love of electrons!• What happens down a group?• Decreases; since the electrons are further from the nucleus, there is a

weaker attraction• What happens across a period?• Increases; since there is an increase in core charge, there is a greater

attraction of the outer shell electrons to the nucleus.

Electronegativity

Electron Affinity• What is it?• The energy release when an electron is added to an atom. Most favorable

toward NE corner of PT since these atoms have a great affinity (“love and happiness”) for e-. (Think of “Jumping for Joy”!)• What happens down a group?• Decreases; since the electrons are further from the nucleus, the atom has no

desire to hang on to it’s electron, so it won’t release too much “Happiness” (energy) if it gains one. • What happens across a period?• Increases; the more electrons an atom has in it’s valence shell, the more

“happy” it will become when it gets closer to completing it shell.

Electron Affinity