PERIODIC PROPERTIES OF THE ELEMENTS Emily Scheerer Justin Green Suh Kwon Abegim Undie _

PERIODIC PROPERTIES OF THE ELEMENTSEmily ScheererJustin Green

Suh KwonAbegim Undie _

7.1 Development of the Periodic 7.1 Development of the Periodic TableTable

Elements have been being discovered since the Elements have been being discovered since the beginning of time.beginning of time.

As the number increased, scientists needed a As the number increased, scientists needed a way to organize the elementsway to organize the elements

In 1869 Dmitri Mendeleev and Lothar Meyer In 1869 Dmitri Mendeleev and Lothar Meyer both published classifications that noted the both published classifications that noted the periodic similarities between elements. periodic similarities between elements.

7.1 Development of the Periodic 7.1 Development of the Periodic TableTableAt the time, there was no knowledge of At the time, there was no knowledge of

atomic numbersatomic numbers However, both scientists arranged elements However, both scientists arranged elements

with increasing weight. with increasing weight. Medeleev is given the credit because he Medeleev is given the credit because he

pronounced his ideas more. For example, he pronounced his ideas more. For example, he predicted the existence and properties of both predicted the existence and properties of both gallium and germanium. gallium and germanium.

http://www.docbrown.info/page03/3_34ptable/PTmendeleev1869.gif

7.1 Development of the Periodic 7.1 Development of the Periodic TableTable

In 1913, Henry Mosley developed the idea of In 1913, Henry Mosley developed the idea of atomic numbers. atomic numbers.

Determined that each element produced Determined that each element produced unique X-ray frequencies, assigning each unique X-ray frequencies, assigning each element a number based on its X-ray element a number based on its X-ray frequency.frequency.

He then identified that the atomic number was He then identified that the atomic number was equal to the number of protons and electrons equal to the number of protons and electrons in the atom.in the atom.

This clarified problems with the weight This clarified problems with the weight arrangement, allowing them to find ‘holes’.arrangement, allowing them to find ‘holes’.

Can you find an example?Can you find an example? (Ar and K)(Ar and K)

7.2 Electron Shells & Sizes of 7.2 Electron Shells & Sizes of AtomsAtoms

What shape does an What shape does an atom have???atom have???

According to the According to the quantum quantum mechanical mechanical number, an atom number, an atom does not have a does not have a defined shape.defined shape.

http://physics.uwstout.edu/geo/bedtime/graphics/atom.jpg


As you move down the periodic table, n As you move down the periodic table, n changes.changes.

Gilbert Lewis: suggested that electrons in Gilbert Lewis: suggested that electrons in atoms are arranged in spherical shells.atoms are arranged in spherical shells.

Radial electron density:Radial electron density:

the probability of finding the probability of finding

the electron at a particular the electron at a particular

distance from the nucleus.distance from the nucleus.


At certain distances, RED shows maxima. At certain distances, RED shows maxima. This indicates higher probability of This indicates higher probability of finding electrons.finding electrons.

How many maximums: due to electrons How many maximums: due to electrons that have the same that have the same nn value. value.

Example: Helium has one maximum Example: Helium has one maximum because it has one because it has one nn value (1) value (1)

Argons has three maximums because of Argons has three maximums because of it’s three it’s three nn values. (1,2,3) values. (1,2,3)

http://upload.wikimedia.org/wikipedia/commons/e/e5/Periodic_table_of_elements_showing_electron_shells.png


Defining atomic size:Defining atomic size: Either nonbonding atomic radius(Van der Waals Either nonbonding atomic radius(Van der Waals

radii)radii) When 2 atoms collide and bounce off of each When 2 atoms collide and bounce off of each

other.other. It’s then the distance from the nucleus to the It’s then the distance from the nucleus to the

outer edgeouter edge

OR bonding atomic radius (covalent radii)OR bonding atomic radius (covalent radii) When two atoms collide and an attractive When two atoms collide and an attractive

interaction leads to a chemical bond.interaction leads to a chemical bond. The distance between the two nuclei, shorter than The distance between the two nuclei, shorter than

the non-bonding atomic radius.the non-bonding atomic radius. Why?Why?


Scientists have developed a variety of Scientists have developed a variety of methods for measuring these distances.methods for measuring these distances.

From observations of these methods, From observations of these methods, each element is assigned a bonding each element is assigned a bonding atomic radius. atomic radius.

Example: IodineExample: Iodine According to observation, the distance According to observation, the distance

separating the nuclei from the electrons is separating the nuclei from the electrons is 2.66 angstroms & therefore the bonding 2.66 angstroms & therefore the bonding atomic radius is 1.33 angstroms. (cut in half to atomic radius is 1.33 angstroms. (cut in half to find radius of one)find radius of one)


To find atomic radii of a bondTo find atomic radii of a bond Add atomic radii of the two bonding atoms Add atomic radii of the two bonding atoms

(NOTE: This is NOT 100% accurate)(NOTE: This is NOT 100% accurate)

~ See Example 7.1 on page 232.~ See Example 7.1 on page 232.

7.2 Electron Shells & Sizes of 7.2 Electron Shells & Sizes of AtomsAtoms Periodic Trends of Atomic Radii:Periodic Trends of Atomic Radii:

Increases from top to bottomIncreases from top to bottom Increasing Increasing nn value means a larger value means a larger

orbital, which means a longer radius.orbital, which means a longer radius. Decreases from left to rightDecreases from left to right

Zeff increases, pulling electrons closer, Zeff increases, pulling electrons closer, making the radius smallermaking the radius smaller

See Example 7.2 on page 233See Example 7.2 on page 233

http://grandinetti.org/Teaching/Chem121/Lectures/PeriodicTrends/index.html


http://grandinetti.org/Teaching/Chem121/Lectures/PeriodicTrends/index.htmlhttp://chemistintheory.blogspot.com/2008_02_01_archive.html

7.3- Ionization Energy

Energy required to remove an electron from the ground state of the atom or ion in standard conditions

http://www.avon-chemistry.com/p_table_sus_ion.jpg

7.3- Ionization Energy

The greater the Ionization energy, the more difficult it is to remove an electron As the ionization energy increases, the

atomic number goes up I1 first ionization

Energy needed to remove the first electron from a neutral atom

I2 second ionization Energy needed to remove 2nd electron

And so forth, for successive removals of additional electrons

7.3 – Ionization Energy

Periodic Trends I1 increases with increasing atomic number

Alkali metals show lowest ionization energy in each row

Noble gases are the highest ionization energy Within each group (up and down), ionization

energy decreases with increasing number HE > Ne > Ar > Kr > Xe

Representative elements (sublevels “s” and “p”) show a larger range of values of I1

F-blocks only show a small variation of values of I1


Factors that affect how strongly an electron is attracted to an atom Nuclear charge (higher charge means there

are more protons) Average distance of the electron from the

nucleus


For instance, attraction increases when nuclear charge increases and distance decreases As the nuclear charge increases, there are

more and more protons The protons have a strong attraction for the

electrons, so the distance decreases Thus, the ionization energy increases


Ionization energy measures the energy changes associated with removing electrons from an atom

Positive value of ionization energy tells us that energy must be put into an atom to remove the electron

7.4 – Electron Affinities

Measures the attraction of the atom for the added electron The more negative the electron affinity, the

greater the attraction between the atom and electron

An electron affinity that is > 0 shows us that the negative ion is higher in energy than the separated atom and electron


Difference between Ionization and Electron Affinities Ionization measures the ease with which

an atom loses an electron Electron affinities measures the ease

with which an atom gains an electron


Periodic Trends Halogens have the most-negative electron

affinities The addition of an electron to a noble gas

requires that the electron reside in a higher-energy sub shell

Occupying a higher-energy sub shell (1s, 2s, 2p, 3s…)

is unfavorable, so the electron affinity is positive

7.5 - Metals, Nonmetals, and Metalloids Properties of atoms include atomic radii,

ionization energies, and electron affinities

No elements exist in nature as an individual atom except for the Noble Gasses.

Periodic Table Grouping

The periodic table is grouped into meals, nonmetals, and metalloids

Metals take up the top left and middle portions of the periodic table, nonmetals occupy the right side (and hydrogen), and metalloids are located between the two

http://www.schenectady.k12.ny.us/users/title3/Future%20Grant%20Projects/Projects/periodictable/Regions.jpg

Metallic Character

The more an element exhibits the physical and chemical properties of a metal, the greater it’s metallic character

Metallic character increases as you go down the periodic table and increases as you go from right to left

http://www.global-b2b-network.com/direct/dbimage/50357240/Electrolytic_Manganese_Metal.jpg

Metals

Characteristics Shiny Conduct heat and electricity Malleable Ductile Solid at Room Temperature

(except mercury) Higher than room

temperature melting points Low ionization energy and

form positive Ions easily Oxidize as they undergo

reactions

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Graphics/MixedMetals(mayFranInt.).jpe

Metals Cont.

Alkali metal ions always have a charge of +1 Alkaline earth metal ions always have a charge of +2 Transition metal ions are mostly +2, but they do have +3

and +1 ions Some transition metals have multiple charges due to their

position on the periodic table Compounds between metals and nonmetals tend to be ionic

2Ni(s) + O2(g) 2NiO(s) Most metal oxides are basic

Metal oxide + water metal hydroxide Na2O(s) + H2O(l) Ca(OH)2(aq) Metal oxide + acid salt + water NiO(s) + 2HCl(aq) NiCl2(aq) + H2O(l)

Nonmetals

Vary in appearance Poor conductors of heat and electricity Melting points are generally lower than metals Have seven diatomic molecules

(Br2,I2,N2,Cl2,H2,O2,F2) React with metals to form salts

Metal + Nonmetal Salt 2Al(s) + 3Br2(l) 2AlBr3(s)

Most nonmetal oxides are acidic oxides Nonmetal oxide + water acid

Dissolve in basic solutions to form salts Nonmetal oxide + base salt + water

http://www.indiamart.com/sujaychemicals/pcat-gifs/products-small/liquid-20bromine_10438902.jpg

Metalloids

Have properties intermediate between those of metals and nonmetals. They may have some characteristics of metallic properties but lack others

Semiconductors Silicon

http://1366tech.com/v1/images/stories/site/silicon.jpg

Group Trends for the Active Metals Elements in a group posses general

similarities Trends occur when you move through a

group or from one group to another

Group 1A: The Alkali MetalsGroup 1A: The Alkali Metals

Soft metallic solids low melting points and low densities Atomic radius increases as you travel

down the column Ionization energy decreases as you

travel down the column Very reactive Combine directly with nonmetals react vigorously with water

2M(s) + H2O(l) 2MOH(aq) + H2(g)

Reacts with oxygen to produce a metal oxide

when placed in a flame they create different colors

http://content.tutorvista.com/chemistry_11/content/us/class11chemistry/chapter12/images/img19.gif

Group 2A: The Alkaline Earth Metals

Harder, more dense, and have higher melting points than the elements of the 1A column

Less reactive than the Alkali metals Calcium and elements below it will readily react with water

at room temperature whereas magnesium will only react with steam and Beryllium will not react at all with water

Because of their relatively high reactivity, the alkaline earth elements are invariably found in nature as compounds of the 2+ ions

http://www.learner.org/interactives/periodic/images/alkaliearthmetals.gif

Group Trends for Selected Nonmetals

Hydrogen

http://library.thinkquest.org/C005858/hydrogen2.jpg

Hydrogen

First element in the periodic table Does not truly belong to any family Occurs as a colorless diatomic gas, H2

under most conditions Owing to complete absence of nuclear

shielding, ionization energy of hydrogen is very high (1312 kJ/mol)

Hydrogen (Cont)

Generally reacts with other nonmetals Reactions can be exothermic Hydrogen reacts with active metals to

form solid metal hydrides

OXYGEN

http://bp1.blogger.com/_83R26vRzoNM/Ruo5uekM8zI/AAAAAAAAAWA/___YOi9YZt4/s320/oxygen1.jpg

Group 6A: Oxygen Group

Metallic character increases as you go down

Oxygen is a colorless gas at room temperature, all others are solid

Oxygen is encountered in two molecular forms, O2 and O3 (O2 is most common)

O3 form is called ozone Two forms of oxygen called allotropes

Oxygen Group (Cont)

Oxygen has a tendency to attract electrons from other elements (called oxidization)

Formation of nonmetal oxides is very exothermic and energetically favorable

Usually creates the stable oxide, the O2- ion

Oxygen Group (cont)

Second most important member of group 6A is sulfur

Sulfur has a tendency to gain electrons from other elements to form sulfides

Halogen

http://www.lightbulbs2u.com/images/halogen_group.jpg

Group 7A: The Halogens

Halogens comes from Greek words halos and gennao, meaning “salt formers”

As we go from 6A to 7A, nonmetallic behavior of elements increases

Melting and boiling points increase with increasing atomic number

Halogens (cont)

Halogens have highly negative electron affinities

Halogens have a tendency to gain electrons from other elements to form halide ions

Halogens react directly with most metals to form ionic halides

Also react with hydrogen to form gaseous hydrogen halide compounds

These compounds are all very soluble

Group 8A: The Noble Gases

All nonmetals that are gases at room temperature

All monoatomic (consiste of single atoms rather than molecules)

Noble Gases (cont)

Completely filled s and p subshells this very stable electron configuration

makes them very unreactive Only the heaviest noble gases form

compounds, and only with very active nonmetals such as fluorine

Documents

PERIODIC PROPERTIES OF THE ELEMENTS Emily Scheerer Justin Green Suh Kwon Abegim Undie _