The Periodic Table

Chapter 6

A quest for accurate reproduction• J.W. Dobereiner – published his triad

classification system (ex. Cl,Br,I similar chemical properties)

• 1860– Scientists agreed upon a method to measure

mass– Are masses related to elemental properties?

• John Newlands– Noticed every 8th element had similar

properties– Law of octaves

The Law of Octaves

Dimitri Mendeleev - 1869

• Organized the periodic table based on increasing atomic mass

• Predicted the properties of unknown elements– Sc, Ge, Ga

P. 181 - Q 24, 25

Henry Moseley

• Arranged elements based on the number of protons

• Determined periodic law– Groups have similar properties– Properties change as you move across a

period– Pattern repeats one period to the next

P.181 - Q – 26, 27

Terminology• Groups (Families) – (IUPAC labels 1-18)• Periods• Representative elements(1A – 8A)

– Wide array of chemical and physical properties

– Group number indicates number of valance electrons

• Transition elements• Metalloids• Metal• Non metals

P. 181 - Q - 31

Metals

• Shiny, smooth• Good electrical and heat conductors• Malleable, ductile• Solid at room temp• Reactive Alkali’s and Alkaline’s (s block)

Transition Metals

• D and F (Inner transitional metals) block• Lanthanides and Actinides

P. 181 - Q 33, 34, 35 – P. 182 – 48, 49, 53, 54

Non-Metals

• Most of p block• gases or brittle solids (Br)• Little luster• Poor conductors• Halogens very reactive• Noble Gases (Inert Gases) - extremely

unreactive due to filled s and p sublevels

P. 181 – 28, 32

Metalloids

• Share properties of metals and non-metals• Heavy step line – B, Si, Ge, As, Sb, Te,

Po, At• Found in p block

P. 181 - 29

Atomic RadiusMetals - Half the distance between

adjacent nuclei in a crystal of an element.

Non Metals - Half the distance between

bonded atoms of the same element (diatomic

molecule).

Atomic Radius – Family Trends

Increases

Atomic charge and occupied energy levels increase.

Occupied orbitals shield electrons in

the outer most energy level from

the pull of the nucleus.

Atomic Radius – Period Trends

decreases

• Increasing positive charge pulls the valence electrons closer to the nucleus.

• Shielding does not influence this trend because the effect is constant. P. 181 - Q - 36 - P. 182 - Q - 50

Ions – Atoms gain or lose electrons to have a complete set of valence electrons (Octet Rule)

Na Na+1

11 protons

10 electrons

11 protons

11 electrons

Empty outer orbital or energy level

makes it smaller. Electrostatic

repulsion decreases.

11 p 10 e

Increased electrostatic repulsion

Cl

17 Protons

17 Electrons

Cl1-

17 Protons

18 Electrons

Ionic Radius – Family Trends

• Principle energy levels increase in

size.

Ionic Radius – Period Trends

3

protons

2 electrons

4

protons

2 electrons

5

protons

2 electrons

6

protons

2 electrons

7

protons

10 electrons

8

protons

10 electrons

9

protons

10 electrons

Electron repulsion decrease Electron repulsion decrease

P. 181 - Q - 41, 42 - P. 182 - Q -52 - P. 183 - Q - 64, 65

Ionization Energy – energy needed for an atom to lose an electron

Be Be+ Be2+ Be3+

kilojoules/mol or kj/mol

1s2 1s2 1s2 1s1

2s2 2s1

1st ionization energies increase as you move across a period due to the increased attraction of the nuclear charge.

The stability of the filled sub level affects the ionization energy.P. 181 – Q - 37, 38, 40 – P. 182 – Q – 55, 58 – P. 183 – Q – 67B

Ionization Energy – Family Trends

Decreases as you move down a family. The further the electron from the nucleus the easier it is to remove.

P. 181 - Q - 39

Electronegativity – a measure of an atom’s ability to attract an electron

P. 181 - Q - 43, 44, 45