Atomic Structure Science 10

Copy: Lithium atom:

Modern Atomic Theory 1.All matter is made of atoms, too small to see. 2.Each element has its own kind of atom. 3.Compounds are formed when atoms of different elements bond to form molecules or ionic compounds. 4.Atoms cannot be created or destroyed in physical or chemical reactions.

What are the 3 major parts of an atom? Proton (+) Neutron (no charge) Electron (-)

Where is everything located? Protons and neutrons are found in nucleus  Center of atom Electrons are found outside nucleus.

The Proton Have a positive (+) charge Found in the nucleus of the atom

The Neutron Do not have a charge Also found in the nucleus of the atom

The Electron Have a negative (-) charge Occupy space outside the atom's nucleus

The Electron Discovered by J. J. Thomson  In 1897 Chemical reactions involve sharing electrons or transferring electrons between atoms

The Nucleus Is the center of an atom Composed of protons and neutrons

The Nucleus Contains most of an atom's mass It was discovered by Ernest Rutherford  In 1911

What is the Electron Cloud Model of the Atom? A model of the atom Pictures the electrons moving around nucleus  In a region called an electron cloud

Made up of ORBITALS  Which are regions in space around the nucleus  Where an electron is likely to be found at any given time It is always moving so we can’t pinpoint it! What is the Electron Cloud Model of the Atom?

Copy & Complete: atom electron cloud neutral consists of which are

Calculating #’s of e - or p + # protons = atomic number # electrons = # protons Atomic Mass number  Found on Periodic Table

Calculating #’s of e - or p + Example: Krypton  # protons = 36  # electrons = 36  Atomic mass = u

Mass Number = # protons + # neutrons If the Atomic Number is 78 and # neutrons is 75, what is the mass #?  = 153 u If the Atomic Number is 78 and # neutrons is 77, what is the mass#?  = 155 u What element is it?  #78 = platinum

Atomic Mass and Isotopes Mass # =  Mass of one atom  Equals # protons + # neutrons in the atom Atomic Mass # =  The average mass of all atoms of an element

Atomic Mass and Isotopes Isotopes  Atoms of one element that have different masses because they have different # neutrons Example:  Carbon-12 has 6 protons + 6 neutrons  Carbon-13 has 6 protons + 7 neutrons

Isotopes of Hydrogen hydrogen-1; hydrogen-2, hydrogen-3

Any Questions? Let’s practice calculating mass # & working with isotopes!

Ions The number of electrons doesn’t always equal the number of protons …  If you have an ion! Formed when an atom gains or loses one or more electrons during a chemical reaction Not neutral!  Has a charge

Charges POSITIVE CHARGE =  The atom LOST electrons NEGATIVE CHARGE =  The atom GAINED electrons

Charges The magnitude (number) of the charge tells you how many electrons are lost/gained Examples:  Li lost 1 electron  charge is +1  O gained 2 electrons  charge is -2

Example: O 2- Oxygen ion has an atomic number of 8 # protons = 8  ALWAYS the same as Atomic number # electrons = 2 more than neutral = 10

Example: K + Potassium ion has an atomic Number 19 It has 19 protons Positive 1 charge = lost one electron = 18 electrons

Any Questions? Let’s practice it all!

Textbook Task Use your notes & textbook (pg ) to answer: #11 (pg 97) “Relative size” = size compared to other particles #5, 6 (pg 104) #4, 9 (pg 109) “Think About It” (pg 105) Use the Periodic Table on page 420

Bohr-Rutherford Diagrams  Named for Niels Bohr (Danish physicist) 1.Circle drawn to represent nucleus 2.Number of protons and neutrons written in circle Sometimes represented as a symbol Example: Sulfur  Protons = neutrons = electrons = 16

Bohr-Rutherford Diagrams 3.Electrons are in orbits Increasingly larger circles drawn around nucleus 4.Maximum number of electrons in each orbits is:  First = 2 electrons  Second = 8 electrons  Third = 8 electrons

Two Variations of the Nucleus Lithium Sulphur

Task Draw a Bohr-Rutherford Model for the first 20 elements in space provided on worksheet  H  Ca  Use a pencil  Hint: Use pg 141 of green textbook if you wish! Don’t forget to add number of protons and neutrons to nucleus!

Practice Task Complete Isotope sheet Remember:  With isotopes: # protons may NOT equal # neutrons!! Hint: use mass number to determine

Lewis Diagrams a.k.a. electron dot diagrams Represent valence electrons  Electrons in outermost shell How to draw:  Start anywhere  Move clockwise  Add one electron on each side Max. 2 e - per side & 8 e - per shell

Task Draw a Lewis Diagram for the first 20 elements in space provided on worksheet  H  Ca Remember: max. e- in shells  1 st = 2  2 nd = 8  3 rd = 8

Trends & Periodic Table Borh Model Turn to pg 141 of green textbook  What relationship do you notice between period # & # of shells? Lewis Diagram Turn to pg 145 of green textbook  What relationship do you notice between group # and # of valence electrons?

Practice Task Draw Lewis Diagrams for:  Selenium  Bromine  Strontium  Radon  Francium Complete Electron Dot handouts

Any Questions???