1. Unit: Chemistry Lesson 1: Introduction to Atoms Essential Questions: 1.) How did atomic theory develop? 2.) What is the modern model of the atom?

2. How did atomic theory develop? Atomos “uncuttable” The smallest particle Atom of an element

3. Dalton  Atoms cannot be broken into smaller pieces Dalton thought that atoms were like hard balls that could not be broken.

4. Dalton’s Model.

5. Thomson  Atoms are made of smaller parts Negatively charged particles Electron in an atom  Atoms contain a positive charge An atom has electrons scattered throughout it like seeds in a watermelon.

6. Thomson’s Model Thomson suggested that atoms had negatively charged electrons set in a positive sphere. Each electron is represented by the symbol e −.

7. Rutherford  An atom is mostly empty space with a positive center The center of an atom Nucleus Positively charged particles Protons in an atom’s nucleus The pit models the nucleus of an atom and the fruit is the space with electrons.

8. Rutherford’s Model According to Rutherford’s model, an atom was mostly open space. The “6+” in the model means that there are six protons in the nucleus.

9. Bohr  Electrons are found in specific orbits

10. Cloud Model  Electrons move within a cloudlike region The amount of energyEnergy level an electron has

11. Modern Model of the Atom Particles in the nucleus Neutron with no electrical charge  An atom has a nucleus made of positively charged protons and neutral neutrons. The nucleus is surrounded by a cloud of negatively charged electrons.

12. Modern Model of an Atom A carbon atom has a nucleus made up of positively charged protons and neutral neutrons. The nucleus is surrounded by a cloud of negatively charged electrons.

13. Particle Charges Number of protons = number of electrons

14. Particle Masses Protons and neutrons make up most of the mass

15. The number of protons Atomic Number in the nucleus

16. Atoms with the same Isotopes number of protons and different numbers of neutrons The sum of the protons Mass number and neutrons in the atom

17. Isotopes of Carbon All isotopes of carbon contain 6 protons. They differ in the number of neutrons. What is the missing information for each isotope?