atomic structure
DESCRIPTION
Atomic Structure. Anthony Gates. Atoms. The smallest particle within an element that still retains its identity in a chemical reaction. Early Ideas. Democritus: believed that the atom was indivisible and indestructible particles. His ideas were later challenged - PowerPoint PPT PresentationTRANSCRIPT
Atomic StructureANTHONY GATES
Today’s Objective
I can describe Dalton’s Atomic Theory.
I can explain the difference between subatomic particles.
Atoms
The smallest particle within an element that still retains its identity in a chemical reaction.
Early Ideas
Democritus: believed that the atom was indivisible and indestructible particles.His ideas were later challenged
Dalton used experimental methods to observe the patterns to which elements combined to form new products to turn Democritus’ ideas into scientific theory.
(John) Dalton’s Atomic Theory
1. All elements consist of tiny indestructible particles called atoms
2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
3. Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Electrons
Discovered by J.J. ThomsonNegatively charged subatomic particlesLocated in the electron cloudWeighs 9.11 x 10-28 grams
So practically nothing
Symbol: e-
Proton
Discovered by Earnest Rutherford Positively charged subatomic particle Located in the nucleus Weighs 1.67 x 10-24 grams
So practically nothing… but still more than an electron.
1amu
Symbol: p+
Neutron
Discovered by James Chadwick Neutral (no charge) subatomic particle Located in the nucleus Weighs 1.67 x 10-24 grams
So practically nothing… but still more than an electron.
1amu
Symbol: n0
Recap
Dalton says what about the atom?1. Elements made up of tiny indestructible particles
2. Atoms are the same as atoms of the same element and different from atoms of different elements
3. Atoms of different elements can mix together or combine to create compounds of atoms in whole number ratios
4. Chemical reactions occur when atoms interact. Atoms cannot change into an atom of a different element.
Recap part dos
Three subatomic particles are…Electrons, protons, neutrons
Electrons are ________ charged.Protons are ________ charged.Neutrons are ________ charged.
Homework
Answer questions from your book:
Pg. 103 # 4, 5
Pg. 108 # 8, 10
Pg. 122 #34, 36, 37
Homework
Bellwork… do this as soon as you sit down
Draw a picture of what you believe an atom looks like.
Learning objectives
I can draw a model of the atom.
I can identify the number of protons, electrons and neutrons in an atom.
Thomson’s Model
Believed atom was a positively charged ball containing electrons
Commonly known as the Plum Pudding model
Earnest Rutherford’s Gold foil Experiment
Nucleus
Tiny central core of an atom and is composed of protons and neutrons.
Rutherford’s Model
Nucleus in the center containing protons and neutrons with a net positive charge
Electrons are evenly distributed around the nucleus taking up most of its volume.
Nucleus Size
If the nucleus was the size of a marble, then the atom would be about the size of a football stadium.
The nucleus contains a large majority of the atoms weight, but only a tiny amount of its size.
Assess for learning
Turn to a partner and describe what the Rutherford model of the atom looks like. Include words like:
nucleus, electrons, electron cloud, protons, and neutrons.
Inquiring minds want to know…
How do we distinguish between the elements? Elements are different because
they contain different amounts of protons.
The Atomic Number (insert booming voice)
Atomic number:The number of protons in a nucleus of an
atom of an elementEx. Hydrogen has one proton and thus its atomic
number is 1.Ex. Oxygen has eight protons and so its atomic
number is 8. This number will NEVER change for an element
Will that be cash or check? … Charge it baby!
An atom naturally has a neutral (zero) electrical charge
If the atomic number tells us the number of protons, which have a positive charge what does it also tell us about the electrons? The atomic number is also the number of electrons
The amount of electrons must equal the number of protons to have a neutral atom.
What about neutrons???
The atomic number will tell us how many electrons and protons there are, but how do we know how many neutrons there are?
Mass Number
Since the majority of the mass is in the nucleus as protons and neutrons, we can look at the weight to help us find the number of neutrons.
Because 1 proton or neutron weighs 1amu, the mass number will be directly related to the number of protons and neutrons.
Since helium has a atomic number of 2, it has 2 protons. If it has a mass number of 4amu, 2amu of the 4amu is the mass are because of the protons, but what about the other two? The other 2amu is the mass of the neutrons. 2amu 2 neutrons.
#Neutron
Number of Neutrons = Mass Number – Atomic Number
Chemical Symbols
Each element has its own chemical symbol. These are one or two letter combinations Examples
Oxygen: OHelium: HeGold: Au
Putting it all together… shorthand
Check for understanding
Phosphorus has an atomic number of 15 and a mass number of 31. Write out this information in shorthand and draw a Rutherford model of an atom for phosphorus.
Bellwork
Draw a Rutherford atom of Fluorine (F).
Learning Objectives
I can calculate the average atomic mass of a given set of isotopes.
Isotopes
Atoms that have the same number of protons, but a different number of neutrons. Because isotopes have different numbers of neutrons, they have different mass
numbers. Isotopes retain their chemical properties since the number of protons and
electrons have not changed. p+ and e- are responsible for chemical properties
Example
Hydrogen has one proton and no neutrons, thus giving it a mass number of 1. Hydrogen-1
An isotope of hydrogen has one proton and one neutron, thus
giving it a mass number of 2. Hydrogen-2
Atomic Masses
Because the mass of a single element is significantly small, they are impractical to work with.
It would instead be easier to use relative masses of atoms and select a reference isotope.
Carbon-12 was selected and 1/12 of the mass of a carbon-12 atom became what is now known as 1 atomic mass unit (amu)
Average Atomic Masses
A sample of almost any element contains a mixture of two or more isotopes.
Certain isotopes occur more often than others. The atomic mass is a weighted average mass of the atoms in a
naturally occurring sample of the element. The weighted average reflects both the mass and the abundance of
each isotope present
Calculating Atomic Mass
Carbon-12 makes up 98.89% of any sample of carbon, while carbon-13 makes up 1.11% of carbon.
Atomic mass of carbon= (12.00amu x .9889) + (13.00amu x .0111)
= 12.01amu
Quiz Practice!!
Draw the Rutherford and Plum Pudding models of Carbon-12.
Plum Pudding Model:
Rutherford Model of Carbon-12
6P6N
e
e
e
e
e
e
Quiz Practice
Element Symbol
Atomic Number
Mass Number
Electrons Protons Neutrons
Te 128
17 18
55 25
247 151
Quiz Practice
Element Symbol
Atomic Number
Mass Number
Electrons Protons Neutrons
Te 52 128 52 52 76
Cl 17 35 17 17 18
Mn 25 55 25 25 30
Cm 96 247 96 96 151
Quiz Practice
What is the average atomic mass of silicon if silicon-28 has an abundance of 92.21%, silicon-29 has an abundance of 4.70% and silicon 30 has an abundance of 3.09%?
Problems
Rutherford’s model could not explain chemical properties of elements. Examples:
Why some compounds give off certain colors when heated in a flame.
Why do some metals glow red, then yellow and even white as they are heated to higher temperatures.
Niels Bohr
Bohr proposed that electrons are found in only in specific circular paths, or orbits, around the nucleus
Each orbit around the nucleus has a fixed energy called energy levels.
Only works well for hydrogen atoms
Ladder Analogy
The farther up the ladder, the higher the energy level and less energy is needed to jump between levels.
Electrons can jump energy levels by gaining energy Quantum: the amount of energy required to
jump an energy level
You can’t stand between rungs
An electron doesn’t exist between energy levels
Bohr’s Model
In order to draw a Bohr model of an atom, simply draw the nucleus with a couple circles around it to symbolize the electron orbits.
Then draw in electrons on the orbits with only two on the most inner circle and up to eight on each of the other orbits.
Ex. Neon is shown to the right.
Practice drawing the Bohr model of carbon
Edwin Schrödinger
Devised a mathematical equation describing the behavior of an electron in a hydrogen atom.
Quantum Mechanical Model Determines the allowed energies an
electron can have and how likely it is to find the electron in various locations around the nucleus.
This is the currently accepted model.
Location by probability
Think of a propeller blade spinning around. It is difficult to locate it at any given moment, but to locate the region where the propeller is most likely to be located at any given moment is very easy.
Electrons move even faster than propeller blades and so determining their exact location is difficult, but determining the region they are most likely to be found is much easier.
Atomic Orbitals
Atomic orbitals: region in space where there is a high probability of finding an electron.
Homework:
Pg. 132# 1, 2, 3, 5, 6
Draw the Bohr model of the following elements:Hydrogen, Beryllium, Nitrogen and Fluorine
Quick Review of the Atom
https://www.youtube.com/watch?list=PLJicmE8fK0EiEzttYMD1zYkT-SmNf323z&v=xazQRcSCRaY&feature=player_detailpage
Review Bell Work
Grab a dry erase board and draw the Bohr model of an atom of Magnesium.
Think about which superhero is your favorite and why. Be prepared to share your answer.