Periodic Table and Electrons

Chemistry

Learning Objectives Atomic Theory and Periodic Table

Essential knowledge and skills:

Distinguish between a group and a period.

Identify key groups, periods, and regions of elements on the periodic table.

Identify and explain trends in the periodic table as they relate to ionization energy, electronegativity, shielding effect, and relative sizes.

Compare an elements reactivity to the reactivity of other elements in the table.

Relate the position of an element on the periodic table to its electron configuration.

Determine the number of valence electrons and possible oxidation numbers from an elements electron configuration.

Write the electron configuration for the first 20 elements of the periodic table.

Essential understandings:

The periodic table is arranged in order of increasing atomic numbers.

The names of groups and periods on the periodic chart are alkali metals, alkaline earth metals, transition metals, halogens, and noble gases.

Metalloids have properties of metals and nonmetals. They are located between metals and nonmetals on the periodic table. Some are used in semiconductors.

Periods and groups are named by numbering columns and rows. Horizontal rows called periods have predictable properties based on an increasing number of electrons in the outer energy levels. Vertical columns called groups or families have similar properties because of their similar valence electron configurations.

The Periodic Law states that when elements are arranged in order of increasing atomic numbers, their physical and chemical properties show a periodic pattern.

Periodicity is regularly repeating patterns or trends in the chemical and physical properties of the elements arranged in the periodic table.

Atomic radius is the measure of the distance between radii of two identical atoms of an element. Atomic radius decreases from left to right and increases from top to bottom within given groups.

Electronegativity is the measure of the attraction of an atom for electrons in a bond. Electronegativity increases from left to right within a period and decreases from top to bottom within a group.

Shielding effect is constant within a given period and increases within given groups from top to bottom.

Ionization energy is the energy required to remove the most loosely held electron from a neutral atom. Ionization energies generally increase from left to right and decrease from top to bottom of a given group.

Electron configuration is the arrangement of electrons around the nucleus of an atom based on their energy level.

Electrons are added one at a time to the lowest energy levels first (Aufbau Principle). Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results (Hunds Rule).

Energy levels are designated 17. Orbitals are designated s, p, d, and f according to their shapes and relate to the regions of the Periodic Table.

An orbital can hold a maximum of two electrons (Pauli Exclusion Principle).

Atoms can gain, lose, or share electrons within the outer energy level.

Loss of electrons from neutral atoms results in the formation of an ion with a positive charge (cation). Gain of electrons by a neutral atom results in the formation of an ion with a negative charge (anion).

ELEMENTS AND THE PERIODIC TABLEWHATS IN THE NAME?

Provide the name and chemical symbol for the element, which sounds similar to a possible correct answer. See number one for an example.

CLUEELEMENTCLUE ELEMENT 1. well drillers decisionboron B24. a spice

2. to press laundry25. a blitz by police

3. policeman26. ..on the Range

4. mothers sisters money 27. of Arabia

5. where dishes are washed28. dull chemistry lecture

6. a foolish prisoner29. Golden Gate Bridge state

7. natives of North America30. bladder or stones

8. water and gin31. European country

9. shown the way32. another European country

10. I sit down to eat33. repair clothes

11. a Ford product34. 50 per cent

12. a popular house plant35. larger than a coyote

13. have the sniffles36. God of the underworld

14. United States citizen37. God of the sea

15. dont take any wooden38. a good . . . (helper)

16. playing a part or role39. to brown a roast

17. . . . . . pop40. girls names calcium Ca

18. a lisper saying listening (many options!)

19. technician

20. Lone Rangers horse

21. endure or tolerate pain

22. what you walk on at home

23. leg joint above calf

CLUE: ium ending read as himELEMENT

1. doctors do thishelium (heel him)

2. doctors do this too

3. funeral homes do this

4. cowboys do this to horses

5. Anything to keep him quiet mother says to father.

6. grab him

7. to get him off my back

History of the Periodic Table

J.A.R. Newlands - 1867 first version of Periodic Table. Newlands arranged the known elements by increasing atomic mass along horizontal rows seven elements long, stated that the 8th element would have similar properties to the first from the series. Newlands called this the law of octaves. Newlands' work failed after Ca in predicting a consistent trend.

Dimitri Mendeleev 1869, Professor of Chemistry at the University of Saint Petersburg (Leningrad). Mendeleev stated that the elements vary periodically (in cycles) according to their atomic masses.

Mendeleev separated his elements and left spaces on his table in order for the periodicity to continue. He then predicted that elements would be discovered to fill these "gaps" in the table. Mendeleev even accurately stated the properties of these elements. Scandium (eka-boron), gallium (eka-aluminum), and germanium (eka-silicon). By 1886 all of the elements predicted by Mendeleev had been isolated.

When Mendeleev's notes show that the periodic system was created in a single day, February 17, 1869. He arrived at his system by puzzling over cards containing the names of the 63 known elements along with their atomic weights and important chemical and physical properties.

Lothar Meyer-1886, also developed a periodic table based on atomic masses, independently of Mendeleev. Meyer had several inaccuracies and some elements were not included. Meyer was the first scientist to introduce the concept of valence as a periodic property. Both Mendeleev and Meyer were awarded the Royal Societies Davy Medal. Mendeleev is given credit because of his accurate property prediction of yet undiscovered elements.

Henry Moseley-1914 was a student of Rutherford. Moseley was studying X-ray formation by high energy electron bombardment. He graphed the square root of the X-ray frequency vs atomic mass. This plot gave a nearly linear line except for three atomic pairs. Ar(39.95)/K(39.10), Co(58.93)/Ni(58.69), Te(127.60)/I(126.90).

When the atoms were plotted according to atomic number, then a linear relationship was established. Moseley stated, "There is every reason to suppose that the integer that controls the X-ray spectrum is the charge on the nucleus."

Periodic Law - The properties of the chemical elements are a periodic function of atomic number.

Why Mendeleev is given Credit in Modern Text Books?

Mendeleev's Table allowed for and was capable of adjusting to future discoveries:

noble gases, new column in 1894-1901

incorporation of the rare earth elements

Moseley's atomic number in 1914

Bohr atom and electronic structure in 1913

discovery of synthetic elements 1939 to present (element 110, 1994)

The Periodic Table

Groupa vertical column of elements in the periodic table; also called a family

Perioda horizontal row of elements in the periodic table

Metalsone of a class of elements that includes a large majority of the known elements; metals are characteristically lustrous, malleable, ductile, and good conductors of heat and electricity

MetalloidsThe elements that border the stair-stepped line are classified as metalloids. The metalloids, or semimetals, have properties that are somewhat of a cross between metals and nonmetals.

Metalloids tend to be economically important because of their unique conductivity properties (they only partially conduct electricity), which make them valuable in the semiconductor and computer chip industry. The metalloids are shown in the following illustration.

Nonmetalsone of a class of elements that are not lustrous and are generally poor conductors of heat and electricity; nonmetals are grouped on the right side of the periodic table

Alkali metalsany metal in Group 1 of the periodic table. (soft, malleable, lustrous, good conductors, MOST REACTIVE family of metals)

Alkaline earth metalsany metal in Group 2 of the periodic table. (higher densities and melting points than alkali metals; not as reactive as alkali)

Halogensany member of the nonmetallic elements in Group 17 in the periodic table. ( MOST REACTIVE Non-Metals; do not occur free in nature; commonly found in sea water, minerals, & living tissues)

Noble gasesany member of a group of gaseous elements in Group 18 in the periodic table. (VERY INACTIVE elements, used in balloons, scuba diving tanks, light bulbs)

Periodic Table Exercise

The following need to be labeled on your periodic table

metals/non-metals

jewellery metals (there are three of them)

m