Periodic Trends

ASANTE DEAN

BLANK PERIODIC TABLE

You will need your personal copy of the Periodic Table.

The Periodic TableThe periodic table is an organizing structure based on the properties of the elements.

The Periodic Table Element GroupsElements belonging to a group typicallyshare several common properties. Also,elements in a group share a commonnumber of valence electrons. (Vertical)

Element PeriodsElements in a period share a highest unexcitedelectron energy level. There are more elementsin some periods than others because thenumber of elements is determined by thenumber of electrons allowed in each energysublevel. (Horizontal)

Chemical FamiliesAlkali Metals Group 1AThe chemical elements found in Group 1 of the periodic table. The alkali metals include: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (RB), Cesium (Cs), and Francium (Fr).

Alkali Earth Metals Group 2AThe alkaline earth metals are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

Transition Metals Middle GroupLocated in the middle of the periodic table. The largest section of elements.

Halogens Group 7AThe halogens or halogen elements are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

Noble Gases Group 8AAll of the elements in Group Zero are noble gases. The list includes helium, neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Don't think that, because these elements don't like to react, we don't use them.

Alkali MetalsAlkali Earth MetalsTransition MetalsHalogensNoble Gases

Metallic CharacterMetallic character refers to the level of reactivity of a metal. Metals tend to lose electrons in chemical reactions, as indicated by their low ionization energies.

Metal Categories Metals Non-Metals Metalloids

Other Information Ability to be reduced (gain electrons) Formation of ionic chlorides and basic oxides Ability to displace hydrogen from dilute acids

The periodic table has different areas for specific types of metals: Alkali metals, Alkali earth metals, transition metals and metalloids.

Metals,Non-metals, and Metalloids

MetalsA metal is a material (an element, compound, or alloy) that is typicallyhard, opaque, shiny, and has good electrical and thermal conductivity.

Metals are generally:Malleable - can be hammered or pressed permanently out of shape

without breaking or crackingFusible - able to be fused or meltedDuctile - able to be drawn out into a thin wire

Non-MetalsNon-metals are not able to conduct electricity or heat very well. Asopposed to metals, non-metallic elements are very brittle, and cannot berolled into wires or pounded into sheets.

Seventeen elements are generally classified as nonmetals; most aregases (hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine,argon, krypton, xenon and radon); one is a liquid (bromine); and a feware solids (carbon, phosphorus, sulfur, selenium, and iodine).

MetalloidsA metalloid is a chemical element with properties in between, or that are a mixture of, those of metals and nonmetals. There is no standard definition of a metalloid, nor is there complete agreement as to which elements are appropriately classified as such.

Metallic Character TrendTHERE ARE TRENDS IN METALLIC CHARACTER AS YOU MOVE ACROSS AND DOWN THE PERIODIC TABLE.

Metallic character decreases as you moveacross a period in the periodic table fromleft to right. This occurs as atoms more readily accept

electrons to fill a valence shell than losethem to remove the unfilled shell.

Metallic character increases as you movedown an element group in the periodictable. This is because electrons become easier to

lose as the atomic radius increases, wherethere is less attraction between the nucleusand the valence electrons because of theincreased distance between them.

Atomic RadiusThe atomic radius of a chemical element is a measure of the size of its atoms.

As you move down a group, atomic radius increases.

As you move across a period, atomic radius decreases.

Electronegativity Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is assigned a value of 4.0, and values range down to cesium and francium which are the least electronegative at 0.7.

Electronegativity Trend

The most electronegative element is fluorine. If you remember that fact, everything becomes easy, because electronegativity must always increase towards fluorine in the Periodic Table.

Electronegativity TrendACROSS A PERIOD

As you go across a period the electronegativity increases. The chart shows electronegativities from sodium to chlorine - you have to ignore argon. It doesn't have an electronegativity, because it doesn't form bonds.

DOWN A GROUP

As you go up a group, electronegativity increases. (If it increases up to fluorine, it must decrease as you go down.) The chart shows the patterns of electronegativity in Groups 1 and 7.

Ionization EnergyThe ionization energy (IE) the amount of energy required to remove an electron of an atom to form an ion.• 1st Ionization Energy: the energy

that is required to remove the first electron

• 2nd Ionization Energy: the amount of energy that is required to remove the second electron, etc.

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