Mr. Conkey Physical Science Chapter 5 The Periodic Table Mr. Conkey Physical Science Chapter 5

Mendeleev’s Periodic Table Mendeleev discovered a principle to organizing all the known elements at that time Mendeleev’s table was composed of single cards with the elements and their known properties He paid special attention to how each element acted in reactions with H₂ and O₂

Mendeleev’s Table (cont.) Within a column, the elements’ mass increase from top to bottom Periodic Table – an arrangement of elements in columns, based on a set of properties that repeat from row to row

Mendeleev’s Table (1898)

Mendeleev’s Prediction Mendeleev left blanks in his table predicting that elements existed that had yet to be discovered He was able to give the best explanation as to how the properties of elements related to their position in his table He used properties of the known elements that were close to the blanks in order to predict properties of the unknown elements

Evidence Supporting Mendeleev’s table The close match between Mendeleev’s predictions and the actual properties of new elements showed the usefulness of his table He developed his table prior to the discovery of protons!

The Periodic Law In the modern periodic table, elements are arranged by increasing atomic number (# of protons) Periods – each row in the table of elements The single electron of hydrogen and the two of helium can fit in the first orbital or energy level (period 1); the second period holds elements whose electrons are in the second orbital and so on

The Periodic Law (cont.) Group – each column on the periodic table Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups Group elements have similar electron configurations (determines their chemical properties) Periodic Law – group elements have similar chemical properties

Atomic Mass Units The four bits of information in an elements “panel” = element name, symbol, atomic mass, and it’s atomic number Atomic Mass Units (amu) – based off of the mass of the isotope carbon-12 (12 amus the standard), it is = to 1/12th of the mass of a carbon-12 atom

Weighted Averages An average between the masses of each isotope of an element See the example over here

Classes of Elements Elements are classified as metals, nonmetals, and metalloids Metals – elements that are good conductors of heat and electric current Metals (aside from mercury) are solids at room temp and most are malleable; many are ductile, meaning ability to spread into wires

Metals on the Periodic Table

Reactivity of Metals Some metals, some of which we have seen (such as Na, Li, and K) are very reactive and some metals aren’t Au versus Na in H₂O, which one is more reactive? Why do you think this is?

Transition Metals Transition metals – elements that form a bridge between the elements on the left and right sides of the periodic table (metals in groups 3 – 12) Were among the first elements to be discovered (e.g. Cu and Ag Many have the ability to form compounds with distinct colors.

Transition Metals (cont.) Lanthanide and actinide series – elements that have more properties in common that most; chemists had a hard time separating them when found in nature!

Nonmetals Nonmetals – elements that are poor conductors of heat/electricity they have a low boiling point resulting in many of them being gases at R.T. those that are solids at R.T. are usually brittle some are very reactive and some not at all, with some in between (F in Group 17 is one of the most reactive nonmetals!) Fluorine even forms compounds with some gases of Group 18, some of the most unreactive elements there are.

BRAIN BREAK!!! https://youtu.be/V1FsO5zaf6M

Metalloids Metalloids – elements with properties that fall between metals and nonmetals Metalloids vary in their conductivity of electricity at different temperatures Si and Ge are good conductors of electricity in higher temps and good insulators at lower temps

Horizontal Distinction of a Period Elements become less metallic and more nonmetallic in their properties when going from left to right within a period Hydrogen is where it is because of it’s electron configuration, not its properties. Group 1 (most reactive metals); Group 17 (most reactive nonmetals

Valence Electrons Valence electrons (e−) = an e− that is in the highest occupied energy level of an atom Atoms have differing #s of energy levels due to how many e− ‘s they have Elements that are in the same groups have the same # of valence e−’s giving them properties that are alike Hydrogen only has one electron (its valence electron); Thus it is included in group 1 as they all have only one valence electron).

Alkali Metals Alkali metals Group 1A (Li – Fr , from top to bottom) 1 valence e− means extremely reactive (think of the video of Na and Li among others) Exist as compounds in nature due to their reactivity! Reactivity goes when moving the alkali metals

Alkali Metals (cont.) Examples of properties of alkali Metals: Na and K are kept in oil so they won’t react with O₂ and H₂O vapor and Na is less dense than H₂O so it floats for a short time until it reacts violently and ignites the H₂ gas being produced by the reaction Cesium reacts with H₂O at temps as low as – 115 °C (- 175 °F)!

Alkaline Earth Metals Alkaline Earth Metals – metals in Group 2A (Be – Ra , from top to bottom) All have 2 valence e−’s Harder than metals of Group 1A; higher melting points too Differences in reactivity of these is shown in reactions (rxns) with H₂O

Alkaline Earth Metal Rxns Sr and Ca and Ba react easily with cold H₂O, where Mg reacts with hot water; Be has no change in H₂O Ca and Mg are involved in biological processes as well as in construction/transportation materials Mg plays large role in photosynthesis (it’s actually in chlorophyll) Mixture of Mg and other metals makes strong, light material (i.e. used in bikes) Ca in bones and teeth; Ca compounds are in chalk, limestone, toothpaste, plaster, coral, and pearls

The Boron Family Group 3 family all have 3 valence e−’s The largest amount of any type of metal in Earth’s crust is Aluminum Less reactive than Mg or Na Strong, light weight, a good electric conductor, and malleable Less energy to recycle than to extract from the bauxite mineral

The Carbon Family Group 4 contains the nonmetal C, two metalloids (Si and Ge), and two metals (Sn and Pb) Metallic properties when going the group Ge better conductor than Si Most of the compounds in the body contain C (except H₂O)

The Nitrogen Family Group 5 has two nonmetals (N and P), two metalloids (As and Sb), and one metal (Bi) Wide range of physical properties N – nonmetal gas; P – solid nonmetal; Bi – dense metal All have 5 valence e−’s N and P used as fertilizers; also used in biological reactions White P – extremely reactive (flames when in the presence of O; Red P – less reactive, used to ignite matches Sb is Antimony; Phosphorus release energy from food.

The Oxygen Family Group 6 has three nonmetals (O, S, and Se) and two metalloids (Te and Po) All have 6 valence e−’s O – the most abundant element in Earth’s crust Many biological uses O₃ - blocks out radiation from sun in the outer atmosphere S – one of the first elements to be found; used to make H₂SO₄ to used to make fertilizers Te – Tellurium; Po- Polonium

The Halogens Group 7 are the Halogens All have 7 valence e−’s All have similar chemical properties, but at R.T. Cl is a gas, Br a liquid, and I a solid Highly reactive nonmetals, especially in rxns with metals

The Noble Gases Group 8 are the noble gases He has only 2 valence e−’s; all the rest have 8 Why is He in Group 8 then? Noble gases are colorless, odorless, and extremely unreactive Useful as insulators; electrical current causes them to emit different colors

Color Coded Periodic Table

To be continued…