Chapter 6

1

Chapter 6

The Periodic Table

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Mendeleev’s Periodic Table (3)

properties (physical & chemical) of the elements repeat in an orderly way from row to row of the table.

Periodicity is the tendency to recur at regular intervals.

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Quick-write

Why isotopes of an element have the same chemical properties?

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Periodic Table of the Elements

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The Modern Periodic Table (2)

The atomic # = # of p+ in the nucleus.

Atomic # increases by 1 as you move from element to element across a pd.

Each pd (except the 1st ) begins with a metal and ends with a noble gas.

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Squares in the Periodic Table

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The Modern Periodic Table (3)

• The properties of the elements change in an orderly progression from left to right.

• The pattern in properties repeats after group 18 (VIIIA).

This regular cycle illustrates periodicity in the properties of the elements.

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The Periodic Law

Periodic Law• states that the physical and chem properties of

the elements repeat in a regular pattern when they are arranged in order of increasing atomic #.

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Relationship of the PT to Atomic Structure

Periodic Table

• elements are arranged according to atomic #

• atomic # tells the # of p+ (and e- too) it has.

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• The lineup starts with H, which has 1 e-.

• He comes next in the 1st pd because He has 2 e-. Li has 3.

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• Notice on the PT that Li starts a new period.

• Why does the 1st pd have only 2 elements?

Only 2 e- can occupy the 1st EL in an atom. The 3rd e- in Li must be at a higher EL.

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• Li starts a new period at the far left in the table and becomes the 1st element in a gp.

A group

• elements in a vertical column.

• Elements have similar chem properties.

• Elements in the ‘A’groups have same # valence e-

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• Gps are numbered from left to right.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A 6A 7A 8A

‘A’ groups elements: representative elements‘B’ group elements: transition elements/transition metals

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3A 4A

1A

5A 6A 7A2A

8A

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Atomic Structure of Elements Within a Pd (2)

• has 1 valence e-.

• has 1 e- at a higher EL than the noble gas of the preceding pd.

• Every period starts with a gp 1 element (H, Li, Na, K, ...)

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Atomic Structure of Elements Within a Pd

• Move across a period to the next…, the # of valence e- increases by 1.

• Gp 18 elements have the max # of 8 valence e- in their outermost EL.

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3A 4A

1A

5A 6A 7A2A

8A

18


• Gp 18 (VIIIA) elements --- noble gases.

• The noble gases, with a full complement of valence e-, are generally unreactive.

Octet configuration→most stable e- configuration except He (duplet)

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The period # (1-7) of an element is the same as the # of its highest EL,

• so the valence e- of an element in the 2nd period are in the 2nd EL.

• A period 3 element such as Al has its valence e- in the 3rd EL.

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3A 4A

1A

5A 6A 7A2A

8A

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Atomic Structure of Elements Within a Gp

• # of valence e- changes from 1 to 8 from left to right across a pd;

• After Gp 18, the pattern repeats.

• For the main gps (A) elements, the gp # is related to the # of valence e-.

• The main gp elements are those in Gps 1(1A), 2(A), 13(3A), 14(4A), 15(5A), 16(6A), 17(7A), and 18(8A).

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• For elements in gps 1(1A) and 2(2A), 4(4A), the gp # = # valence e-.

• For elements in gps 13(3A), 14(4A), 15(5A), 16(6A), 17(7A), and 18(8A), the 2nd digit in the gp # is = to the # valence e-.

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3A 4A

1A

5A 6A 7A2A

8A

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• Because elements in the same gp have the same # of valence e-, → similar chemical properties.

• Na is in Gp 1 → 1 valence e-.

• Because other elements in gp 1 also have 1 valence e-, → similar chem properties.

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• Cl is in Gp 17 (7A) and has 7 valence e-.

• All the other elements in gp 17 also have 7 valence e- → similar chem properties.

• Throughout the PT, elements in the same gp have similar chem properties because the have the same # of valence e-.

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6.2

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5 categories:

alkali metals in Group 1(6; except H),

alkaline earth metals in Group 2 (6),

halogens in Group 17(VIIA), and

noble gases in Group 18(VIIIA) (octet).

transition metals (B groups)

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Because the PT relates gp and pd # to valence e-, it’s useful in predicting atomic structure and, chem properties.

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• e.g. O, in Gp 16(6A) and Pd 2, has 6 valence e- (the same as the 2nd digit in the gp #), and these e- are in the 2nd EL (because O is in the 2nd pd).

• O has the same # of valence e- as all the other elements in Gp 16(6A) → similar chem properties.

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e- in Energy Levels—Group 16

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Physical States and Classes of the Elements

• Nonmetals occupy the upper-rt-hand corner.• 18 nonmetals; 11 gases at ‘usual’ temp

• Metalloids (7) :located along the boundary between metals and nonmetals.

• close to 80% (≈90) of the elements are metals occupying the entire left side (except H) and center .

• All metals except Hg exist as solid at ‘usual’ temps

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Physical States and Classes of the Elements

Elements are classified as

basis on physical and chem properties

• Metals (alkali, alkaline earth, transition)

• metalloids, or

• Nonmetals

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elements

metals metalloids

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Metals

With the exception of Sn, Pb, and Bi, metals have 1, 2, or 3 valence e-.

Metals luster, conduct heat and electricity usually bend without breaking malleable ductile

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Metals (2)

• All metals except Hg are solids at ‘usual’ temp;

• Hg is a liquid at ‘usual’ temperature

• most have extremely high m.p. and b.p. m.p. of Fe : about 1700°C

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Transition Metals (3)

• The elements in Gps 3 (3B) thru 12 (2B) → transition elements/metals.

• All metals.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A 6A 7A 8A

• Unpredictable chem properties complex atomic structures.

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• 2 series of elements (58-71 and 90-103) are placed below the main body of the table.

• separated from the main table the table very wide.

• inner transition elements.

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• The 1st series (lanthanides) follow element # 57, lanthanum.

• 14 elements

• rare earth elements (0.01 %).

• similar properties.

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Metals (7)

• The 2nd series of inner transition elements, the actinides

• radioactive

• none beyond U (92) occur in nature.

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lanthanides and actinides

lanthanides and actinides • Unpredictable chem properties• complex atomic structures.

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Nonmetals (1)

Some nonmetals are abundant in nature

• The nonmetals O and N make up 99 % of Earth’s atm.

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Nonmetals (2)

C is found in more cpds than all the other elements combined.

The many cpds of C, N, and O are important in a wide variety of applications.

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Nonmetals (3)

nonmetals (most) don’t conduct electricity and heat

are brittle when solid.

Many are gases (11) at ‘usual’ temp

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Nonmetals (4)

Their m.p. and b.p. are lower than those of metals.

With the exception of C, nonmetals have 5, 6, 7, or 8 valence e-.

lack the luster of metals.

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Properties of Metals and Nonmetals

Metals Nonmetals

Mainly hard solids Soft solids or gases

Bright metallic luster Non-lustrous, various colors

Good conductor of heat and electricity

Poor conductor

Solids are easily deformed

May be hard or soft; usually brittle

Loosely held valence e- Tightly held valence e-

High m.p. and b.p Low

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Metalloids

Metalloids

• have some chemical and physical properties of metals and nonmetals.

• lie along the border between metals and nonmetals.

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Metalloids

• Si is probably the most well-known metalloid (computer chips)

• six others

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Metalloids (3)

A semiconductor

• is an element that

• does not conduct electricity as good as a metal,

• but does conduct slightly better than a nonmetal.

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Semiconductors and Their Uses

• TV, computer, handheld electronic games, MP3, cell phones, and calculator are electrical devices

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Semiconductors and Their Uses

metals generally are good conductors of electricity,

nonmetals are poor conductors,

semiconductors fall in between the 2 extremes.

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Trends in Atomic Size/radius (1)

atomic radius• ½ of the distance between the nuclei of 2 atoms

of the same element when the atoms are joined.

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Trends in Atomic Size/radius (2)

Group Trendincreases from top to bottom within a gp and

Periodic Trenddecreases from left to right across a pd.

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Shielding Effect

Shielding effect

• go down a gp of the PT, elements possess more and more EL/subshells/orbitals

• EL/subshells/orbitals are blocking the attractions of the e- in the outer shells by the nucleus.

• Also the e- in the inner shells are repelling the e- in the outer shells preventing them to move closer to the nucleus.

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Trends in Atomic Size/radius

Atomic Size/radii decreases

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56

Group and periodic trend

Atomic sizes/radii decreasing

Atomic sizes/radii increasing

57

Explain Periodic Trend—atomic sizes

Periodic Trend e.g. Li and F

same EL and # orbitals

i.e. same shielding effect

# p+ increases

nuclear attraction increases

pulls e- towards the nucleus

smaller (atomic radii…)

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Explain Group Trend—atomic sizes

Group trend

• # p+ increases; stronger nuclear attraction

• # EL & orbitals increases; higher shielding effect on the nuclear attraction

• Shielding effect is more significant than the effect of increase in nuclear attraction

• Bigger (atomic radii ….)

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Trends in Atomic Size

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Trends in Ionization Energy (1)

Ionization energy amt of energy required to remove an e- from an

atom in gaseous state e.g. Na → Na+ + e-

Na ionNa atom Valence e-

• 1st I.E.: energy required to remove the 1st e- from an atom.

• 2nd I.E. : energy required to remove an e- from an ion with a 1+ charge. (needs a lot more energy)

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Group Trend decreases down a gp (means less energy is

used to remove an e-.)

Periodic Trend increases across a pd

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Group and period trend

Ionization energy increasing

Ionization energy decreasing

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I.E. increases

I.E. d

ecreases

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Explain Period Trend—I.E. (7)

Periodic Trend

• shielding effect remains the same (why?)• # p+ increase• stronger nuclear attraction• atom size decreases• valence e- closer to the nucleus• more tightly attracted• not so likely to lose• need more energy to remove an e-• Higher I.E.

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Explain group trend—I.E. (6)

Group Trend

shielding effect increases (why?)

atomic sizes increases (more EL & orbitals)

valence e- are farther from nuclei

valence e- not so tightly attracted/held

easier to lose

lower I.E.

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Trends in Electronegativity (1)Electronegativity (e- affinity) (of an element) the ability of an atom of an element to attract

e- when the atom is in a cpd.

Periodic Trend increases across a pd.

Group TrendDecreases down a gp.

e.g. in a H2O molecule, the e- of H atoms move closer to the O atom (attracted by the nucleus of O atom; O is more electronegative

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Group and period trend

EN increasing

EN decreasing

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Increases

Incr

ease

s

Shielding

Electronegativity

decreases

electronegativity

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Explain group Trend—Electronegativity(2)

Group Trend• shielding effect increases (why?)• nuclear attraction becomes less significant

(why?)• atoms are getting bigger• the nucleus is farther from the surface of the

atom.• nuclear attraction not strong enough to attract

more outside e- (e- of other atoms in a cpd)

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Explain Periodic Trend—Electronegativity(3)

Periodic Trend same # EL and orbitals→same shielding effect# p+ increase→ increase in nuclear attraction atom smaller; nucleus closer to the surface of

atom more likely to attract e- of another atom in the

cpd higher EN

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Trends in Electronegativity (4)

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decreasin

g

increasin

g

Decreases

Increases

I.E.

I.E. electronegativity

electronegativityAtomic size

Atomic size

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Atomic Size

IncreasesIn

cre

ase

s

Shielding

Electronegativity

Ionization energy

decreases

Decreaseselectronegativity

Ionization energy

Atomic size

76

Ions

An ion

• an atom or group of atoms that have a +ve or –ve charge

• formed when e- are transferred between atoms

• Cation (+ve) and anion (-ve)

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Cations and Anions

Group IA, IIA, IIIA elements (metals) lose e- to form cations.

Na → Na+ + e-

Mg → Mg2+ + 2e-

Al → Al3+ + 3e-

Na atom Na ion

Cations: • +vely charged ions • metals form cations by losing valence e-

Mg ion

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Cations and Anions

Group VA, VIA and VIIA (nonmetals) form ions by gaining e-.

N + 3 e- → N3-

O + 2 e- → O2-

Cl + e- → Cl-

N atom Nitride ion

Oxide ion

Chloride ion

Oxygen atom

Chlorine atom

Anions• -vely charged ions• nonmetals form anions by gaining e-

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Ions (2)

+ve and -ve ions form when e- are transferred between atoms.

Cation

e-

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Ions (3)

+ve and -ve ions form when e- are transferred between atoms.

Anion

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CST Problem 1

Which of the following atoms has six valence electrons?

A magnesium (Mg)

B silicon (Si)

C sulfur (S)

D argon (Ar)

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CST problem 2

Which of the following is a monatomic gas at STP?

A chlorine

B fluorine

C helium

D nitrogen

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CST problem 3

Which of the following elements has the same Lewis dot structure as silicon?

A germanium (Ge)

B aluminum (Al)

C arsenic (As)

D gallium (Ga)

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CST problem 3

Which of the following ordered pairs of elements shows an increase in atomic number but a decrease in average atomic mass?

A Ag to Pd

B Co to Ni

C Ge to Sn

D Cr to Mo

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CST problem 4

Iodine would have chemical properties most like

A manganese (Mn)

B tellurium (Te)

C chlorine (Cl)

D xenon (Xe)

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CST problem 5

Graph showing ionization energy changes with atomic number

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CST problem 5 (cont.)

The chart above shows the relationship between the first ionization energy and the increase in atomic number. The letter on the chart for the alkali family of element is

A W.

B X.

C Y.

D Z.

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The End

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Transition Elements

Transition Elements

2 types of transition elements--classified based on their e-confign.

transition metals and

inner transition metals.

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Trends in Ionic Size

• Relative Sizes of Some Atoms and Ions

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Chapter 6

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