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CHAPTER 6: Periodic Table. Development of Periodic Table. Mendeleev Contributions – made very first periodic table p.t. arrangement: elements ordered by increasing atomic mass. Development of Periodic Table. 3) Noticed periodic pattern (repetition) in element properties

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development of periodic table
Development of Periodic Table
  • Mendeleev
  • Contributions – made very first periodic table
  • p.t. arrangement: elements ordered by increasing atomic mass
development of periodic table1
Development of Periodic Table

3) Noticed periodic pattern (repetition) in element properties

- elements placed in groups w/ similar properties

- Left gaps for substances yet to be discovered

slide5
4) errors: when new elements discovered, several elements on his table didn’t fit right

- had different properties

moseley
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
Modern Periodic Table
  • Boxes contain:
    • Element name
    • Element symbol
    • Atomic number
    • Atomic mass
modern periodic table1
Modern Periodic Table
  • Arrangement – increasing atomic number

a) groups – columns (vertical)

b) periods – rows (horizontal)

two divisions of elements
Two Divisions of Elements
  • Main Group Elements – groups 1A, 2A and 13-18A

(s & p block)

two division of elements
Two Division Of Elements
  • Transition Elements – group 3-12B elements (d block)
classifying elements
Classifying Elements
  • Metals

– elements w/ shine

– solid @ room temp

– conducts heat & electricity

– malleable: put into thin wires

– ductile: pound into sheets

metals
Metals

a) Alkali Metals – group 1A (except H)

- highly reactive, very soft

b) Alkaline Earth Metals – group 2A

- less reactive and denser than alkali metals

c) Transition Metals – d-block (group 3-12B)

metals1
Metals

d) Inner transition metals – f-block

i) Lanthanide Series – row 1 of f-block

ii) Actinide Series – row 2 of f-block

La

Ac

nonmetals
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
Metalloids
  • Defn – BORDER THE STAIRSTEP LINE 

- Have similar chem & phys props as both metals

and nonmetals

slide16

Alkali metals

Halogens

Noble Gases

Alkaline earth metals

Transition Metals

Lanthanides

Actinides

organizing elements by electron configuration
Organizing Elements By Electron Configuration
  • Valence Electron – electrons in highest energy level

atoms in same group have similar chemical

props b/c they have same # of valence e-

valence electrons and period
Valence Electrons And Period
  • The period indicates what energy level the valence electrons are located on
  • Ex: [Ar] 4s2 3d10 4p1

3 Valence e-

on 4th energy

level

valence electrons and group number
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
Ex Problems
  • Tell the group, period, and block where these elements are located

[Ne] 3s2

[He] 2s2 2p4

[Kr] 5s2 4d105p5

2

group –

period –

block –

group –

period –

block –

16

group –

period –

block –

17

3

2

5

s

p

p

periodic trends
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
Atomic Radius (size)
  • Defn – distance from center to edge of electron cloud
  • Period Trend – decreases from left to right

Why?

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

electrons (- charge)

atomic radius
Atomic Radius
  • Group Trend – increases from top to bottom

Why?

electrons occupy higher energy levels and are farther from the nucleus

Period 1

Period 2

Period 3

atomic radius1
Atomic Radius
  • Summary

decreases

increases

slide25
Ion
  • Defn – atom w/ a positive or negative charge

- atom lost or gained electrons

- # protons ≠ # electrons

cation
Cation
  • Defn – positive ion (atom lost e-)

- more protons than electrons

  • Comparing atom size vs. its cation size

A

A+

atom A

cation of atom A

cations are SMALLER than its original atom

anion
Anion
  • Defn – negative ion (atom gained e-)

- more electrons than protons

  • Comparing atom size vs. its anion size

A-

A

atom A

anion of atom A

anions are LARGER than its original atom

ion summary
Ion Summary

A-

A

A+

<

<

cation

atom

anion

ionization energy
Ionization Energy
  • Defn – energy required to remove an electron from an atom
  • Period trend – IE increases from left to right

Why?

increased nucleus charge has greater hold on valence e-

ionization energy1
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)

slide31

Period 1

Period 2

Period 3

ionization energy2
Ionization Energy
  • Summary

increases

decreases

ex problem
Ex problem
  • Rank these atoms from increasing to decreasing ionization energy: Ba, Cs, Cl

increases

decreases

Cl

Cs

Ba

Cl > Ba > Cs

electronegativity
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
electronegativity1
Electronegativity
  • Summary

increases

decreases

ex problem1
Ex problem
  • Rank these atoms from high to low electronegativity: O, Sr, Mg

increases

decreases

Mg

O

Sr

O > Mg > Sr

ad