CHAPTER 6:Periodic Table

Development of Periodic Table

► Mendeleev1) Contributions – made very

first periodic table

2) p.t. arrangement: elements ordered by increasing atomic mass

3) Noticed periodic pattern (repetition) in element properties- elements placed in groups w/ similar properties

- Left gaps for substances yet to be discovered

Development of Periodic Table

Mendeleev’s Periodic Table (1871)

4) errors: when new elements discovered, several elements on his table didn’t fit right- had different properties

Moseley

►periodic table arrangement: elements ordered by increasing atomic number

►Periodic Law – when elements arranged by increasing atomic number, their physical & chemical properties show a periodic pattern

Modern Periodic Table

► Boxes contain:1) Element name2) Element symbol3) Atomic number4) Atomic mass

Modern Periodic Table

►Arrangement – increasing atomic numbera) groups – columns (vertical)b) periods – rows (horizontal)

Two Divisions of Elements►Main Group Elements – groups 1A,

2A and 13-18A (s & p block)

Two Division Of Elements►Transition Elements – group 3-12B

elements (d block)

Classifying Elements

►Metals – elements w/ shine

– solid @ room temp– conducts heat & electricity– malleable: put into thin wires– ductile: pound into sheets

Metals

a) Alkali Metals – group 1A (except H)- highly reactive, very soft

b) Alkaline Earth Metals – group 2A- less reactive and denser

than alkali metalsc) Transition Metals – d-block (group

3-12B)

Metals

d) Inner transition metals – f-block

i) Lanthanide Series – row 1 of f-blockii) Actinide Series – row 2 of f-block

La

Ac

Nonmetals

►Defn - gases or brittle, dull looking solids

- poor conductors of heat & electricity

a) Halogens

b) Noble Gases

- group 17A

- highly reactive- group 18A

- very unreactive/stable

Metalloids

►Defn – BORDER THE STAIRSTEP LINE

- Have similar chem & phys props as both metalsand nonmetals

Alk

ali

meta

ls

Alk

alin

e e

art

h m

eta

ls

Transition Metals Halo

gens

Noble

Gase

s

LanthanidesActinides

Organizing Elements By Electron Configuration

►Valence Electron – electrons in highest energy level

atoms in same group have similar chemicalprops b/c they have same # of valence e-

Valence Electrons And Period

►The period indicates what energy level the valence electrons are located on

►Ex: [Ar] 4s2 3d10 4p13 Valence e-

on 4th energylevel

Valence Electrons and Group Number

►# of valence electrons equals group number (only for main group elements)

► exception: Helium(in group 18, but has 2 valence e- only)

Ex Problems

►Tell the group, period, and block where these elements are located

[Ne] 3s2

group –

period –

block –

[He] 2s2 2p4

group –

period –

block –

[Kr] 5s2 4d105p5

group –

period –

block –

2 1716

3 2 5

s p p

Periodic Trends

►There are certain patterns that occur with the elements as you go across and down the periodic table

which atom is the biggest? smallest?which atom is most reactive/least stable?

Atomic Radius (size)

►Defn – distance from center to edge of electron cloud

►Period Trend – decreases from left to rightWhy?

increasing # of protons (+ charge) in nucleus has a greater attraction for

electrons (- charge)

Atomic Radius►Group Trend – increases from top to

bottomWhy?

electrons occupy higher energy levels and are farther from the nucleus

Period 1 Period 2Period 3

Atomic Radius

►Summary

decreases

incr

ease

s

Ion

►Defn – atom w/ a positive or negative charge- atom lost or gained electrons- # protons ≠ # electrons

Cation

►Defn – positive ion (atom lost e-)- more protons than electrons

►Comparing atom size vs. its cation size

A

atom A

A+

cation of atom A

cations are SMALLER than its original atom

Anion

►Defn – negative ion (atom gained e-)- more electrons than protons

►Comparing atom size vs. its anion size

A

atom A

A-

anion of atom A

anions are LARGER than its original atom

Ion Summary

A A-A+

atomcation anion

< <

Ionization Energy

►Defn – energy required to remove an electron from an atom

►Period trend – IE increases from left to rightWhy?

increased nucleus charge has greater hold on valence e-

Ionization Energy

►Group Trend – IE decreases from top to bottom

Why?atomic size increases, valence e-

are farther away so easier to remove (less energy required)

Period 1

Period 2

Period 3

Ionization Energy

►Summary

increases

decr

ease

s

Ex problem

►Rank these atoms from increasing to decreasing ionization energy: Ba, Cs, Cl

Cs Ba

Cl

increases

decr

ease

s

Cl > Ba > Cs

Electronegativity

►Defn – relative ability of an atom to attract electrons in a chemical bond “how badly does atom want electrons” while in a bond

►Period Trend – increases from left to right

►Group Trend – decreases from top to bottom

Electronegativity

►Summary

increases

decr

ease

s

Ex problem

►Rank these atoms from high to low electronegativity: O, Sr, Mg

Sr

Mg O

increases

decr

ease

s

O > Mg > Sr