Periodic trends l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 26

Periodic Trends PowerPoint PPT Presentation


  • 130 Views
  • Uploaded on
  • Presentation posted in: General

Periodic Trends. Mrs. Coyle Chemistry. Part I – Atomic Size. Atomic Radius. Measures as distance from nucleus to nucleus and divided by 2. Unit commonly used is pm picometer= 10 -12 m Example: iodine atomic radius 140pm. How does atomic radius change across a period?.

Download Presentation

Periodic Trends

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Periodic trends l.jpg

Periodic Trends

Mrs. Coyle

Chemistry


Part i atomic size l.jpg

Part I – Atomic Size


Atomic radius l.jpg

Atomic Radius

  • Measures as distance from nucleus to nucleus and divided by 2.

  • Unit commonly used is pm

  • picometer= 10-12m

  • Example: iodine atomic radius 140pm


How does atomic radius change across a period l.jpg

How does atomic radius change across a period?

  • It is smaller to the right.

  • Why?

  • More protons in the nucleus higher electrical force pulls electrons closer to nucleus.


How does atomic radius change down a group l.jpg

How does atomic radius change down a group?

  • It is larger down the group.

  • Why?

  • Valence electrons are at higher energy levels and are not bound as tightly to the nucleus because they are screened or shielded ( pushed away) by other electrons in inner levels.


Slide6 l.jpg

Note

  • There are some exceptions. Example column 13.


The periodic table and atomic radius l.jpg

The Periodic Table and Atomic Radius


Example l.jpg

Example:

Which is larger: a lithium atom or a fluorine atom?

A lithium atom


Example9 l.jpg

Example:

  • Which is larger: an arsenic atom or a sulfur atom?

  • An arsenic atom


Part ii ionization energy l.jpg

Part II – Ionization Energy


Ionization energy l.jpg

Ionization energy

  • Ionization energy is the amount of energy needed to remove an electron from a gaseous atom.

    • First ionization energy – 1+

    • Second ionization energy – 2+


Slide12 l.jpg

Ion

  • Positive ion---removal of electron

  • Negative ion--- addition of electron


How does ionization energy change down a group l.jpg

How does ionization energy change down a group?

  • The first ionization energy decreases as you move down a group.

  • Why?

    • The size of the atom increases.

    • Electron is further from the nucleus.


How does ionization energy change across a period l.jpg

How does ionization energy change across a period?

  • The first ionization energy increases as you move from left to right across a period.

  • Why?

    • Nuclear charge increases while shielding is constant.

    • Attraction of the electron to the nucleus increases.


Ionic size l.jpg

Ionic size

  • Metallic elements easily lose electrons.

  • Non-metals more readily gain electrons.

    How does losing or gaining an electron effect the size of the atom (ion) ?


Positive ions l.jpg

Positive ions

  • Positive ions are always smaller that the neutral atom. Loss of outer shell electrons.


Negative ions l.jpg

Negative Ions

  • Negative ions are always larger than the neutral atom. Gaining electrons.


Ion size trends in periods l.jpg

Ion size trends in periods.

  • Going from left to right there is a decrease in size of positive ions.

  • Starting with group 5, there is sharp increase followed by a decrease in the size of the anion as you move from left to right.


Ion size trends in columns l.jpg

Ion size trends in columns.

  • Ion size increases as you move down a column for both positive and negative ions


Electronegativity the ability of an atom in a bond to pull on the electron linus pauling l.jpg

Electronegativity: the ability of an atom in a bond to pull on the electron. (Linus Pauling)


Electronegativity l.jpg

Electronegativity

  • When electrons are shared by two atoms a covalent bond is formed.

  • When the atoms are the same they pull on the electrons equally. Example, H-H.

  • When the atoms are different, the atoms pull on the electrons unevenly. Example, HCl


Trends in electronegativity l.jpg

Trends in Electronegativity

  • Electronegativity generally decreases as you move down a group.

  • Electronegativity of the representativeelements (Group A elements) increases as you move across a period.


Electronegativities of some elements l.jpg

Electronegativities of Some Elements

Element Pauling scale

F 4.0

Cl 3.0

O 3.5

N 3.0

S 2.5

C 2.5

H 2.1

Na 0.9

Cs0.7


Slide25 l.jpg

Note

  • Most electronegative element is F

    (EN 4.0)

  • Least electronegative stable element is Cs

    (EN 0.7)


Summary l.jpg

Summary

Nuclear charge increases

Shielding increases

Atomic radius increases

Ionic size increases

Ionization energy decreases

Electronegativity decreases

Shielding is constant

Atomic Radius decreases

Ionization energy increases

Electronegativity increases

Nuclear charge increases


  • Login