The Periodic Table A Terrific Tool

Dmitri Mendeleev Used properties to sort into groups Originally based on atomic mass

In the modern table… Elements are arranged in order of increasing atomic number Henry Mosley

Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

GROUPS

PERIODS

A little review The number of protons in an atom (atomic number) identifies the element The sum of the protons and neutrons in an atom (mass number) identifies an isotope. Common notations that represent isotopes include:  14 C, carbon-14, C-14 (where 14 is the mass number)

An atom of C-12 and an atom of C-14 differ in (1) Atomic number (2) Atomic mass (3) Nuclear charge (4) Number of electrons

All isotopes of a given atom have (1) The same mass number and same atomic number (2) The same mass number but different atomic numbers (3) Different mass numbers but the same atomic number (4) Different mass numbers and different atomic numbers

In which list are the elements arranged in order of increasing atomic mass? (1) Cl, K, Ar (2) Fe, Co, Ni (3) Te, I, Xe (4) Ne, F, Na

Elements divided into: METALS NONMETALS METALLOIDS

METALS Good conductors of heat and electric current Solids at room temperature (except Hg) Ductile, malleable, luster Silvery gray color except copper and gold

Alloys Homogenous mixtures composed of two or more elements, at least one of which is a metal Important because their properties are often superior to those of their component elements

Alloys NameComposition (by mass) Sterling SilverAg 92.5% Cu 7.5% Cast ironFe 96% C 4% Stainless steelFe 80.6% Cr 18.0% C 0.4% Ni 1.0%

NONMETALS Greater variation in physical properties: many different states, many different colors Poor conductors Brittle

Activity of Ms and NMs Activity of METALS increases as you go down within a group Activity of NONMETALS decreases as you go down a group

What is a property of most nonmetallic solids? (1) High thermal conductivity (2) High electrical conductivity (3) Brittleness (4) malleability

METALLOIDS Heavy, stair-step line Properties of both metals and nonmetals Behavior controlled by environment  Ex. Silicon

Which list of elements contains three metalloids? (1) Si, Ge, Po, Pb (2) As, Bi, Br, Kr (3) Si, P, S, Cl (4) Po, Sb, I, Xe

Allotropes Some elements exist in two or more forms in the same phase. These forms differ in their molecular or crystal structure and hence in their properties. Allotropes of oxygen Allotropes of carbon Oxygen (O 2 )diamond Ozone (O 3 )graphite buckminsterfullerene

The P.T. displays: The symbols and names of the elements, along with information about the structure of their atoms  Alkali metals Group 1  Alkaline earth metals Group 2  Halogens (halos=salt; genesis=to be born) Group 17/7A  Noble Gases Group 18/8A

Elements can be sorted into: Representative elements Transition elements Inner transition metals BASED ON THEIR ELECTRON CONFIGURATIONS

For Groups 1, 2 and 13-18: Elements within the same group have the same number of valence electrons (helium is the exception) and therefore similar chemical properties.

REPRESENTATIVE ELEMENTS 1A-8A Display a wide range of physical and chemical properties (metals, nonmetals, metalloids) s and p sublevels occupied Group # = # of e - in highest occupied energy level (VALENCE)

Transition Elements 1. They are usually high melting point metals. 2. They have several oxidation states. 3. They usually form colored compounds.

TRANSITION ELEMENTS Transition Metals:  Group B elements usually displayed in main body of a periodic table  Copper, silver, gold and iron  Presence of e - in d orbitals

TRANSITION ELEMENTS Inner Transition Elements  Below the main body of the periodic table  Presence of e - in f orbitals  “rare-earth elements” Some more abundant than other elements

Which group of the periodic table contains atoms with a stable outer electron configuration? (1)1 (2)8 (3)16 (4)18

Periodic Trends

Trends The succession of elements across the same period and down the same group demonstrate characteristic, periodic trends:  Atomic radius  Ionic radius  Electronegativity  First ionization energy

Across a Period There are more protons pulling on the outer electrons  Bigger nuclear charge

Down a Group Increase in the number of principle energy levels SHIELDING EFFECT

Atomic Size Also called atomic radius Defined as how far the valence electrons are from the nucleus

Atomic Size In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

In a GROUP: As the Atomic # increases (top to bottom), nuclear charge increases and the # of occupied energy levels increases.  Increase in (+) charge draws e - closer to the nucleus  Increase in the # of occupied orbitals shields e - in the valence shell from the attraction of p + in the nucleus

The SHIELDING EFFECT blocks the attraction of the nucleus for the outer electrons …is greater than the effect of the increase in nuclear charge Therefore, the atomic size increases top to bottom down a group

In a PERIOD: From left to right each element has 1 more p + and e - across a period e - are added to the same principal energy level. The shielding effect is constant for all elements in a period. The increasing nuclear charge pulls the e - in the valence closer to the nucleus and the atomic size decreases.

Trends in Atomic Size

Which list of elements is arranged in order of increasing atomic radii? (1) Li, Be, B, C (2) Sr, Ca, Mg, Be (3) Sc, Ti, V, Cr (4) F, Cl, Br, I **Check Table S**

IONS An atom that has gained or lost one or more electrons Has a positive or negative charge.

Oxidation Number A positive or negative number assigned to an atom to indicate its charge when combined in a compound The oxidation of an uncombined element is zero

Oxidation Numbers

Ions- Metals Atoms of metallic elements tend to lose one or more electrons and therefore form (+) cations  Na 1+ Electrons are pulled in much closer so the radius decreases.

Ions- Nonmetals Atoms of nonmetallic elements tend to gain one or more electrons and therefore form (-) anions  Cl 1- Same e - config as a noble gas but has fewer protons. Electrons repel each other and the radius increases.

Ionic Size Cations are always smaller than that atoms from which they form. Anions are always larger than the atoms from which they form.

What is the total number of electrons in a Cu + ion? (1) 28 (2) 29 (3) 30 (4) 36

What electron configuration is correct for a sodium ion? (1)2-7 (2)2-8 (3)2-8-1 (4)2-8-2

Ionization Energy The energy required to remove an electron from an element

First Ionization Energy Energy to remove first electron Tends to decrease from top to bottom within a group and increase from left to right across a period Can help predict what ions will form (Table 6.1)

In a GROUP: As the size of the atom increases, nuclear charge has a smaller effect on the electron in the highest occupied energy level- shielding effect Therefore, less energy is required to remove an electron from further energy levels, therefore the 1st ionization energy is lower.

From which of these atoms in the ground state can a valence electron be removed using the least amount of energy? (1) Nitrogen (2) Carbon (3) Oxygen (4) Chlorine

In a PERIOD: First i.e. tends to increase from L  R Nuclear charge increases; shielding effect stays constant. Therefore, there is an increase in the attraction of the nucleus for an electron, so it takes more energy to remove an electron from its atom Figure 6.19 on p.175

Electronegativity The ability of of an element to attract electrons when the atom is in a compound.

Trends in Electronegativity In general, electronegativity decreases from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period. F  Fr/Cs

Which of the following atoms has the greatest tendency to attract electrons? (1) barium (2) beryllium (3) boron (4) bromine

Summary in Periodic Trends Figure 6.22 on p. 178

Reference Table S Table S- Properties of Selected Elements

Trends in Metallic Properties Metals want to lose electrons Form positive (+) ions (cations) Low electronegativity Low first ionization energy Metallic properties decrease as you go to the right across a period Metallic properties increase as you go down a group Most metallic: francium  most active metal

Trends in nonmetallic properties Nonmetals want to gain electrons Form negative (-) ions (anions) High first ionization energy High electronegativity Nonmetallic properties increase as you move right across a period Nonmetallic properties decrease as you move down a group Most nonmetallic: fluorine  most active nonmetal

Which of the following Group 15 elements has the greatest metallic character? (1) nitrogen (2) phosphorous (3) antimony (4) bismuth

Which are two properties of most nonmetals? (1) High ionization energy and poor electrical conductivity (2) High ionization energy and good electrical conductivity (3) Low ionization energy and poor electrical conductivity (4) Low ionization energy and good electrical conductivity