Variation in Atomic Structure: Isotopes and Ions

Monday November 14th and Tuesday November 15th

Question:

• The mass of an atom of an element can change without changing the element…

What subatomic particles must change in order for this to occur?

Neutrons; changing the protons would change the element!!!

protonproton

neutronneutron

electronelectron

BERYLLIUMISOTOPES

BERYLLIUMISOTOPES

Isotopes

• Element with same amount of protons but different amounts of neutrons.

EXAMPLE OF AN ISOTOPE

EXAMPLE OF AN ISOTOPE

ClCl3535

1717 ClCl3737

1717

20 20 NEUTRONSNEUTRONS

ATOMIC MASSATOMIC MASS

1818 NEUTRONSNEUTRONS

ATOMIC NUMBERATOMIC NUMBERATOMIC NUMBERATOMIC NUMBER

Average Atomic Mass

• Average mass of all isotopes of an element

• Relative to the other elements around.

• Determined by taking the sum of mass of all the isotopes multiplied by their relative abundances

Calculating Atomic mass

• Example: Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?

• ∑ (85 amu X .722) + (87 amu X .278)– 61.37amu + 24.186 amu)

Answer: 85.56 amu

Practice: Magnesium has three isotopes

Magnesium-24 78.70 % abundant

Magnesium-25 10.13% abundant

Magnesium-26 11.17% abundant

Determine average atomic mass of magnesium. Units are amus

How are ions produced?

Elements gain or lose electrons Valence electrons- outer energy level

electrons Octet Rule- All elements want to be like the noble

gases (group 18), so they gain or lose electrons in order to become stable.

Column= # of valence electrons from 1-8 Exception- Helium- has 2 valence electrons

Determined from electron dot diagrams

Electron Dot Diagrams

Steps to follow: 1) Write the symbol of the element listed.

2) Surround the symbol with valence electrons.

Electron Dot Diagrams of first 20 elements

What are ions?

Atoms of an element that differ in electrons Two types:

Cations- lose electrons; become positively charged Column 1= loses 1 Column 2= loses 2 Column 3= loses 3

Anions- gain electrons; become negatively charged Column 15= gains 3 Column 16= gains 2 Column 17= gains 1 Column 18= stable

Writing Ions

• Write the elements symbol

• Using a superscript, write a positive or negative charge.– Positive- loses electrons– Negative- gains electrons

• Write the number lost or gained next to the charge.

SOME ATOMS GAIN ELECTRONS

SOME ATOMS GAIN ELECTRONS

O

--

----

--

--

--

--

--

O-2

--

----

--

--

--

--

--

----

ATOM’S IONIC CHARGE = ATOM’S IONIC CHARGE = # PROTONS - # ELECTRONS # PROTONS - # ELECTRONS

ATOM’S IONIC CHARGE = ATOM’S IONIC CHARGE = # PROTONS - # ELECTRONS # PROTONS - # ELECTRONS

Making Ions: Practice

• Draw the electron dot diagrams and the ions formed by the following elements: – Hydrogen– Lithium– Magnesium– Oxygen– Aluminum– Phosphorus(Hint: Ions should include the element’s symbol and a

superscript charge showing the amount of electrons gained or lost)

The Location of Electrons

Wednesday November 15th and Thursday November 16th

Energy Levels• Energy levels- determine the amount of

energy an electron has.

• Energy levels= n = quantum number• n= 1= 1st energy level• n= 2 = 2nd energy level• n=3= 3rd energy level• All the way up to the 7th energy level

Sublevels

• Organized on

the periodic table

into S,P,D, F

• Energy level=

# of sublevels

S Sublevel

P Sublevel

Orbitals• probable location to find an electron• n2= # of orbitals for each energy level

S: 1 orbital P: 3 orbitalsD: 5 oribtals F: 7 orbitals

• Three rules to follow when electrons fill orbitals. – Aufbau Principle

• Each electron occupies lowest energy orbital first

– Pauli Exclusion Principle• two electrons can occupy 1 orbital

– Hund’s Rule• Electrons occupy each orbital with one electron before filling

the orbital with two

To Review:

• Electrons fill to

become stable.

• No more than 2

electrons per orbital

• 2n2= # of electrons

per energy level

Electron Configurations

Displays the following: # of each energy level letter of each sublevel # of each electron in that sublevel as

a subscript

Electron Configurations Examples:

• Hydrogen• 1s1

• Helium – 1s2

• Lithium– 1s2 2s1

• Beryllium– 1s2 2s2

More Examples• Boron

– 1s2 2s2 2p1

• Carbon– 1s2 2s2 2p2

• Nitrogen– 1s2 2s2 2p3

• Oxygen– 1s2 2s2 2p4

• Fluorine– 1s2 2s2 2p5

• Neon– 1s2 2s2 2p6

In-class Practice• Draw electron configurations for the rest of

the first 20 elements on the periodic table.

Bohr Models

Friday November 18th and Monday November 28th

Making Bohr Models.

1) Determine the # of protons, neutrons and electrons in the element.

2) Draw a circle to represent nucleus. Inside of circle, write # of protons and neutrons.

3) Draw circles around the nucleus based on how many levels the element has.

4) Insert electrons according to the rules learned about electron location.

1st energy level= 2 electrons2nd energy level= 8 electrons3rd energy level= 8 electrons (can be up to 18)4th energy level= 8 electrons (can be up to 32)

Bohr Model Practice

• Hydrogen-

• Helium-

• Lithium-

Draw Bohr Models for the rest of the 1st 20 elements.

Homework

Chapter Review

Pennium Lab