The Periodic Table Properties of Elements and Trends
The Periodic Table Properties of Elements and Trends
Mendeleev • The original periodic table was created by Dmitri Mendeleev. • He organized the table by atomic mass. • He predicted existence of 3 missing elements (Ga, Sc, Ge)
Modern Periodic Table • The modern periodic table is organized by atomic number. Henry Mosely
• Vertical columns called groups or families • Horizontal rows called periods also represent the shells or energy levels • The basis of periodic law is repeating patterns.
Major Categories of Elements • 1) metals 2) non-metals 3) metalloids • Metals are found to the left of the “staircase” • Non-metals are found to the right of “staircase” • Metalloids are found “on” the staircase
Properties of Metals • • Solid at room temperature (except Hg) Shiny, Have luster Malleable Ductile Generally have high melting points Good conductor of heat and electricity Have metallic bonds
Properties of Non-metals • • • Can be solid, liquid or gas at room temp S examples C, S, I 2 L Br 2 G O 2, Ne, F 2 Allotropes- different molecular forms of the same element (different properties, too) O 2 and O 3 • Dull, lack luster • Brittle • Poor conductors
Properties of Metalloids • Solid at room temperature • Semi-conductors • Have varying properties that can be metallic or non-metallic
• Metals tend to lose electrons to form a full valence shell and + ions. • Non-metals tend to gain electrons to form a full valence shell and – ions.
Groups on the Periodic Table • In general, elements found within the same group have similar chemical and physical properties. • This is mainly due to the fact that they have the same number of valence electrons.
Alkali Metals (Group I) • Metals • Have one valence electron • Tend to lose that one electron to become a more stable ion. • Rarely found in natural state.
Lithium(Li), Sodium(Na), and Potassium(K) • Three examples of alkali metals • VERY reactive metals • Exist as solids at room temperature, but are soft • Silvery-white or grayish in color
Lithium
Applications of Lithium • Compounds containing Li have many applications: • lithium hydroxide is used to absorb carbon dioxide in space vehicles • lithium is used in the manufacture of special high strength glasses and ceramics • sometimes, lithium-based compounds such as lithium carbonate (Li 2 CO 3) are used as drugs to treat manic-depressive disorders.
Sodium
Applications of Sodium • • • Sodium compounds include: "common salt" (sodium chloride, Na. Cl), "soda ash" (sodium carbonate, Na 2 CO 3) "baking soda" (sodium bicarbonate, Na. HCO 3) "caustic soda" (sodium hydroxide, Na. OH), are important to the paper, glass, soap, textile, petroleum, chemical, and metal industries • sodium vapor is used in lamps for street lighting
Potassium
Applications of Potassium • The metal is the seventh most abundant and makes up about 1. 5 % by weight of the earth's crust. • Potassium is an essential constituent for plant growth and it is found in most soils. • It is also a vital element in the human diet.
Comparing 3 Alkali Metals Lithium Sodium Potassium
Alkaline Earth Metals (Group II) • Metals • Have two valence electrons • Tend to lose the two electrons to become a more stable ion
Magnesium(Mg), Calcium(Ca) and Strontium(Sr) • • Examples of alkaline earth metals Exist as solids at room temperature Silvery white or grayish white in color Fairly reactive metals
Magnesium
Applications of Magnesium • Magnesium is the eighth most abundant element in the earth's crust although not found in it's elemental form. • used in flares and pyrotechnics • it is lighter than aluminum, and is used in alloys used for aircraft, car engine casings, and missile construction
Calcium
Applications of Calcium • Forms more than 3% of the earth’s crust • Is an essential constituent of leaves, bones, teeth, and shells • is a component of Portland cement
Strontium
Applications of Strontium • fireworks (red flame), flares • 90 Sr is a radioactive isotope produced by nuclear fallout. 90 Sr has the potential for use as lightweight nuclear producing electricity • used to produce glass for color television tubes
Halogens Group 17 • • Have 7 valence electrons Non-metals (F, Cl, Br, I) F, Cl (gases), Br (liquid), I (solid) Tend to gain one electron to form a more stable ion • Extremely reactive
Fluorine
Fluorine • Used as a toothpaste additive, in refrigerator coolants, and in Teflon
Chlorine
Chlorine • Used in water purification and bleach.
Noble Gases Group 18 • Very stable because of filled valence shell. • Do not react in the presence of other elements (relatively inert) • Xe can react with Fluorine (more later)
Argon
Argon • Used in light bulbs and lasers.
Xenon • Used in UV lamps and sun lamps in tanning salons.
Transition Metals • • Also known as “heavy metals” Tend to be very dense Have varying reactivity Have multiple oxidation states (can form more than one ion) • Have colorful ions (in solution)
Copper
Copper • Used to make the Statue of Liberty, pennies, water pipes and more.
Nickel
Nickel • Used to make coins, knives, forks and rechargeable batteries.
Silver
Silver • Used in silverware, jewelry, mirrors, and batteries.
Lanthanide and Actinide Series • Rare earth metals • Above 92 they are man-made and are unstable
Periodic Trends • Trends occur in the periodic table in the following areas: -reactivity -metallic/non-metallic character -atomic radius* -ionization energy* -ionic radius -electronegativity* * Found on Table S
Reactivity (metals) • Atoms react when they gain, lose or share electrons (bonding). Metals – lose e-, bigger loser = more reactive Across a period, metal reactivity decreases. Down a group, metal reactivity increases.
Reactivity (non metals) • Atoms react when they gain, lose or share electrons (bonding). non metals – gain e-, Better gainer = more reactive Across a period, non metal reactivity increases. Down a group, non metal reactivity decreases.
Metallic Character • Remember best metal is Francium (lower left) • Metallic character is relative to Fr. • Across a period (away from Fr) metallic character decreases. • Down a group (towards Fr) metallic character increases.
Non metallic Character • Remember best non metal is Fluorine (upper right) • Non metallic character is relative to F. • Across a period (towards F) non metallic character increases. • Down a group (away from F) non metallic character decreases.
Atomic Radius Atomic radius provides a basis for the size of an atom. Atomic radius is equal to half the distance between 2 neighboring nuclei of the same element.
Group Trends in Atomic Radius • As you move down a group in the periodic table, atomic radius generally increases. • This is due to the fact that as you move down a column the number of shells increases making the atom bigger.
Atomic Radius increases Group Trends in Atomic Radius
Period Trends in Atomic Radius • As one moves across a period of the Periodic Table, atomic radius generally decreases. • This is due to the fact that each successive element has one more proton that increases the nuclear charge. This positive charge pulls on the outermost shell and makes the atom smaller.
Period Trends in Atomic Radius Atomic radius decreases
Ionization Energy • The energy required to remove an electron from an atom is known as the FIRST IONIZATION ENERGY. • To remove a second electron requires what is called the SECOND IONIZATION ENERGY.
Group Trends in Ionization Energy • As one moves down a group, first ionization energy generally decreases. • This is due to the fact that as one moves down a group the atomic size increases and outermost e- further away from the nucleus (the nucleus doesn’t have as much pull so it takes less energy to remove).
An Analogy: Football • Remember, as atomic size increases, the outermost electrons become further away from the nucleus. • If a football player is holding the ball very close to himself, it is more difficult to remove it from him. • If a football player is holding the ball far away from his body is becomes much easier (less energy) to remove it.
First ionization energy decreases Group Trends in Ionization Energy
Period Trends in Ionization Energy • As one moves across a period of the Periodic Table, first ionization energy generally increases. • This is due the fact that as atomic number (number of protons) increases, so does nuclear charge. • The stronger nuclear charge makes it more difficult to remove an electron.
Another Analogy: Football • Increasing atomic number and therefore nuclear charge would be analogous to the football player building strength. • It then becomes more difficult to get the ball from him (ionization energy increases).
Stop and Practice How would you describe the atomic radius of a period-2 alkaline earth metal with that of a period-4 alkaline earth metal? Answer: The atomic radius of a period-2 alkaline earth metal is smaller than that of a period-4 alkaline earth metal.
More practice Which has a larger atomic radius within the same period: a halogen or an alkali metal? Answer: An alkali metal has a larger atomic radius than a halogen within the same period.
More Practice Which element in group 16 has the highest first ionization energy? In period 2? Answer: Oxygen and neon
Ion Formation • Atoms with low ionization energies (they lose electrons easily) form positive ions (CATIONS). Metals do this. • Atoms with high ionization energies tend to gain electrons to form negative ions (ANIONS). Non-metals do this.
Ionic Size (Cations) • The gaining or loss of an electron affects the size of atom (that turns into an ion). • Positive ions are smaller than the atom they are made from.
Cation Size • When an electron is lost from an atom, the nucleus now has more pull on the outer energy level making the ion SMALLER. MINUS ONE ELECTRON
Ionic Size (Anions) • Negative ions are larger than the atom they are made from.
Anion Size • When an electron is gained the nucleus now has less pull on the outer energy level making the ion LARGER. PLUS ONE ELECTRON
Trends in Ionic Radius (Both Cations and Anions) Ionic Radius increases Ionic Radius decreases
Electronegativity • Can be defined as an atom’s ability to attract electrons. • Expressed in arbitrary units on Table S of your Reference Tables. • Non-metals tend to have higher electronegativities because they like to gain electrons. atoms electrons
Trends in Electronegativity • In one sentence THE CLOSER AN ATOM IS TO FLUORINE ON THE PERIODIC TABLE, THE HIGHER THE ELECTRONEGATIVITY. ** Fluorine has the highest electronegativity on the Periodic Table (4. 0).
Summary of Electronegativity Trends Electronegativity decreases Electronegativity Increases
Stop and Practice How does the ionic radius of sodium compare with that of cesium? Boron with fluorine? Answer: Sodium is smaller than cesium. Boron is larger than fluorine.
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