1. Inside the Atom
Chapter 1

2. Models of the Atom What is a scientific model?
 a representation of an object or system
can be used to make a prediction
can be tested
 must be able to explain as many characteristics of the observations as possible
must be as simple as possible
all models have limitations

3. Models of the Atom
Greek philosophers devised a theory of atoms, or tiny particles.
John Dalton combined the idea of elements with the Greek theory of the atom.
Matter is made up of atoms.
Atoms cannot be divided into smaller pieces
All atoms of an element are exactly alike.
Different elements are made of different atoms.
Dalton’s theory was tested by William Crookes and his cathode-ray tube experiment.

4. The negatively charged electrons are attracted to the positive plate and repelled by the negative plate

5. J.J. Thompson discovered negatively charged particles, electrons, which are a part of every atom.
Thompson revised Dalton’s model to include a sphere with positive charge and negatively charged electrons spread evenly within the positive charge.
The negatively charged electrons and the positive charge in the sphere neutralize each other.

6. Earnest Rutherford tested Thompson’s model, which was found to be an inaccurate model of the atom.
Golf foil experiment
Only a large positive charge would cause the particles to bounce back!

7. An atomic model with a nucleus was developed.
The positively charged proton is located in a very small space at the center of an atom
Most of an atom is empty space occupied by nearly massless electrons.
Electrically neutral particles, neutrons, are also located in the nucleus.
The number of electrons equals the number of protons in an atom.
The electron cloud model explains the unpredictable wave behavior of electrons, which could be anywhere in the area surrounding the nucleus.

8. We are going to model our own atom according to the electron cloud model.
Half will be protons and half will be electrons.
The entire room is our atom.

9. The Simplest Matter Elements – matter made up of one kind of atom.
There are 112 known elements
90 naturally occurring elements, 25 synthetic elements – made by scientists

10. Periodic Table – Chart that organizes and displays information about the elements.
Atomic number – the top number in the element’s periodic table block
Tells the number of protons in the nucleus of each atom of that element
The number of protons remains constant in every atom of an element.

11. Mass number – number of protons plus number of neutrons
Isotopes – atoms of the same element that have different numbers of neutrons
Mass number – number of protons plus number of neutrons
Atomic mass – the number found below the element symbol
The average mass of an atom of an element
The unit used for atomic mass is the atomic mass unit, which is given the symbol u.

12. Elements fall into three general groups characterized by similar properties.
Metals – most of the elements
Shiny luster
Good conductors of heat and electricity
Most are solids at room temperature
Malleable , or can be shaped
Ductile, or can be drawn into wires without breaking

13. Nonmetals – found on the right side of the periodic table
Dull in appearance
Poor conductors of heat and electricity
Many are gases at room temperature
Brittle, cannot change shape without breaking
96 percent of the human body is made up of nonmetals.

14. Metalloids – found between the metals and nonmetals on the periodic table
Have characteristics of both metals and nonmetals
Do not conduct heat and electricity as well as metals
All are solids at room temperature

15. Compounds and Mixtures
Substance – matter that has the same composition and properties throughout
Compound – substance whose smallest unit is made up of atoms of more than one element
Formula – tells which elements make up a compound as well as how many atoms of each element are present
The subscript number tells how many atoms of the preceding element are in the compound
No subscript is used when only one atom of the element is present
A given compound is always made of the same elements in the same proportion.

16. Bonus question: Questions: H2O How many elements are there? C6H12O6
How many oxygen atoms are there?
KOH
How many atoms are there?
C2Cl3F3
How many Carbon atoms are there?
NaCl
Bonus question:
C10H7N3S

17. Mixture – two or more substances mixed together which don’t make a new substance
Unlike compounds, the proportions of the substances can be changed without changing the identity of the mixture
Examples: air, blood…
Can separate mixtures easily
Homogeneous mixtures – the same throughout
Heterogeneous mixtures – you can see the different parts