Periodic Table

The Periodic Table

• Historical development of the periodic table: Highlights– Mendeleev (1869): Put the elements into columns

according to their properties. Generally ranked elements by increasing atomic mass.

– Other guys: Pretty much did the same thing

Metals

• These are general properties and may not be true for all metals.

– Malleable: Can be pounded into sheets.– Ductile: Can be drawn into wires– Good conductors of heat and electricity– High density (usually)– High MP and BP (usually)– Shiny– Hard

Nonmetals:

• Bonds between the atoms are highly localized, causing each of the properties below. Again, these are general properties and may not be true for all nonmetals.– Brittle– Poor conductors of heat and electricity– Low density– Low Melting Point and Boiling Point (many are

gases!)

Metalloids:

• The bonding in metalloids is between that of metals and nonmetals, so metalloids have properties of both.– Some metalloids are shiny (silicon), some are not (gallium)– Metalloids tend to be brittle, as are nonmetals.– Metalloids tend to have high MP and BP like metals.– Metalloids tend to have high density, like metals.– Metalloids are semiconductors of electricity – somewhere

between metals and nonmetals. This makes them good for manufacturing computer chips.

Families/groups(the terms are synonymous and will be used interchangeably)

• These are elements in the same columns of the periodic table.

• Elements within families/groups tend to have similar physical and chemical properties.– They have similar chemical and physical properties

because they have similar electron configurations.

Periods:

• Elements in the same rows of the periodic table

– Elements in the same period have valence electrons in the same energy levels as one another.

– Though you’d think this was important, it has very little effect on making the properties of the elements within a period similar to one another.• The closer elements are to each other in the same period,

the closer are their chemical and physical properties.

Other fun locales in the periodic table:

• Main block elements: These are the s- and p- sections of the periodic table (groups 1,2, 13-18)

• Transition elements: These are the elements in the d- and f-blocks of the periodic table.

• The term “transition element”, while technically referring to the d- and f-blocks, usually refers only to the d-block.

• Technically, the d-block elements are the “outer transition elements”

• Technically, the f-block elements are the “inner transition elements”

Major families in the periodic table:

• Label these on your periodic table if they are not already labeled.

Families/groups

Alkali Metals

• Group 1 (except for hydrogen) – •

– Most reactive group of metals– Flammable in air and water– Form ions with +1 charge– Low MP and BP (MP of Li = 181º C, Na = 98º C)– Soft (Na can be cut with a knife)– Low density (Li = 0.535, Na = 0.968)

Alkaline Earth Metals

• Group 2: – Reactive, but less so than alkali metals– React in air and water (show Ca reacting in water)– Form ions with +2 charge– Low MP and BP, but higher than alkali metals (MP

of Ba= 302º C, Mg = 649ºC– Soft, but harder than alkali metals– Low density, but higher than that of alkali metals

(Ca = 1.55, Mg = 1.74).

(Outer) Transition Metals

• Groups 3-12:•

– Note: These are general properties and may vary from transition metal to transition metal! There are many exceptions to each of these rules!

– Stable and unreactive.– Hard– High MP and BP (Fe = 1535º C, Ti = 1660º C).– High density (Fe = 7.87, Ir = 22.4)– Form ions with various positive charges (usually include +2 and

several others)– Used for high strength/hardness applications, electrical wiring,

jewelry

Lanthanides and Actinides – The Inner Transition Metals

– Lanthanides (4f section)• Also called the rare earth metals, because they’re rare.• Usually intermediate in reactivity between alkaline earth metals and

transition metals.• High MP and BP• Used in light bulbs and TV screens as phosphors.

– Actinides (5f section)• Many have high densities• Most are radioactive and manmade• Melting points vary, but usually higher than alkaline earth metals.• Reactivity varies greatly• Used for nuclear power/weapons, radiation therapy, fire alarms.

Group 17: Halogens

– The most highly reactive nonmetals.– Highly volatile – F and Cl are gases, Br is a volatile

liquid, and I is an easily sublimed solid.– Strong oxidizers – they readily pull electrons from

other atoms.– Diatomic – form molecules with formula of X2

– Form ions with -1 charge– Used in water treatment and chemical production –

Cl2 was used as a chemical weapon in World War I.

Group 18: Noble Gases

– Highly nonreactive– Used to provide the atmosphere in situations

where you don’t want chemical reactions to occur (light bulbs, glove boxes, etc).

Hydrogen – “The Weirdo”

• Has properties unlike any other element– Diatomic – H2

– Can form either a +1 or -1 charge– Relatively nonreactive unless energy is added

(under most conditions) – it can form explosive mixtures with oxygen (as it did in the Hindenburg explosion)