Periodic properties of the elements

Patterns of main group elements Atomic size Ionic size Ionic radii Chemical reactivity

Atomic size Size of atom increases in any group as you go down the column because the valence electrons are found in energy levels farther from the nucleus. Size of atom decreases across a period. The addition of protons “pull in” the electrons from the same energy level.

Ionic size Important factor for chemical reactivity, solutions, and structure Metallic Ions (groups 1-3 that lose valence electrons) form are smaller than original element because the remaining electrons are at a lower energy level are attracted more strongly to the nucleus. Nonmetallic ion (groups 5-7 that gain valence electrons) but the nuclear charge doesn’t increase so the electrons are held less tight and the ionic radii is larger than neutral atom

Pattern in ionic radii Ionic radii increases down the table in a group because of the increasing distance of the valence electrons.

Main group reactivity Elements that lose electrons (bonding) the larger the atom, the more readily it gives up electrons, the more reactive. Cesium most reactive of metals. Elements that gain electrons, the larger the atom, the less the attraction for the electrons, the less reactive. It’s more reactive smaller. Fluorine most reactive of nonmetals.

Alkali metal Group 1: Li, Na, K, Rb, Cs, Fr. Soft, silvery – white metals, good conductors heat and electricity, highly reactive – not found free in nature Lose s valence electron to form +1 ion (like previous noble gas) Cs is most reactive metal Reacts with water to form hydroxide (base / alkaline) Na, K supply positive ion for transmitting nerve impulse for muscle contraction K essential nutrient for plants

Alkaline Earth Metals Group 2: Be, Mg, Ca, Sr, Ba, Ra +2 ion, less reactive than alkali, but still too reactive to be found free in nature. Mg alloys are used in jet engines, MgO protects from further reaction with oxygen. Mg is needed for photosynthesis, Ca needed for bones Hydroxyapatitie Ca5(PO4)3OH. Sr is used in fireworks, bright red

Group (1)3 B (metalloid), Al, Ga, In, Tl are metals, less reactive than previous, silvery, soft, tend to share electrons instead of forming ionic compounds. +3 ion, Al most abundant metallic element in Earth’s crust, turns to oxide preventing further reaction. Hall-Heroult process removes from ore, many items made of Al B found in cleaning solutions Ga melts in your hand

Group 14 – carbon family C (nonmetal),Si and Ge (metalloids), Sn, and Pb (metals) +4,Share electrons during reactions, Sn / Pb lose electrons C – living things / food, pencil lead, diamond Si – Sand (SiO2), Glass, sealant, ceramics, semiconductors Sn – protective coating on steel can for food storage, bronze, solder, pewter, foil Pb – batteries, pewter

Group 15 N, P (nonmetals),As, Sb (metalloids), Bi (metallic) -3, gain 3 electrons N – proteins, DNA, RNA, 78% of air – not usable so bacteria on legumes it to ammonia (fertilizer) and nitrate, lightning (NO) P – Phosphate group (PO4-3), ATP, red matches As – with Ga for electronics Sb – improves hardness and corrosion resistance in alloys.

Group 16 O, S, Se, Te (nonmetals) Po (metalloid) -2 gains 2 electrons O – most abundant element, 21% atmosphere, water, ozone – pollutant lower “smog” protect from UV in upper atmosphere. Hydrogen peroxide (H2O2), Sulfur – Frasch process, sulfuric acid – batteries, rubber Se – security and mechanical devices, photocopier

Group 17 Halogen: F, Cl, Br, I, At, -1 gains 1 electron, very reactive and not found free, diatomic – bound to itself F most reactive, toothpaste, I antibacterial, thyroid gland Cl – kill bacteria in water, bleach Br – photographic film – light sensitive coating on film.

Group 18 – Noble gas He, Ne, Ar, Kr, Xe and Rn Full valence shell, inert. Kr and Xe have F compounds He- used in balloons because “lighter than air” and less reactive than Hydrogen.

Trends in properties of transitional elements Have high melting point and boiling point (except zinc column); increases from Group 3 to maximum group 5/6 and decrease across the remainder. Tungsten – highest metal, Mercury – lowest, liquid at room temperature Have many oxidation state due to involvement of the d electrons (close energy to s orbital) in chemical bond (only heavy main group display this property)

Trends in atomic size of transitional elements Similar trend to main group, just not as dramatic. Atomic radii increase as go down the group Atomic radii decreases at you go down a period.

Iron Needed in biology – Hemoglobin Magnetic Separated from Ore (oxides) in blast furnace, to produce pig iron where slag is drawn off. Iron with additives (carbon or transitional) to give steel with different properties. Surgical steel is hardest. Heat treating – iron reacts with carbon to form a carbide that dissolves in steel. Damascus steel

Other transitional elements Iron triad – Fe, Co, Ni Platinum group – Ru, Rh, Pd, Os, Ir, Pt: used as catalyst to speed up reactions Coinage metals- Cu, Ag, Au: used for coins because malleable, less reactive, rare Chromium – Corrosion – resistance, self protecting, variety of colored compounds Zinc – corrosion – resistance, galvanize – surface coating of steel, Brass when add Cu.

Inner transitional elements Little change in atomic size in period 5 and 6 so they have similar properties Cerium – misch metal alloy, flint for lighters, glass polish Neodymium – welder’s shield Some in control rods – nuclear (absorb neutrons) electronics

Actinides Uranium – radioactive element for nuclear fuel Plutonium – nuclear fuel, power source in pacemakers and buoys.