1. Chapter 4: Section 1

2.  The Atom is the smallest particle of an element

3.  The Atomic theory grew as a series of models that developed from experimental evidence. As more evidence was collected, the theory and models were revised.

4.  All elements are composed of atoms that cannot be divided

5.  All atoms of the same element are exactly alike and have the same mass. Atoms of different elements are different and have different masses

6.  An atom of one element cannot be changed into an atom of another element.

7.  Atoms cannot be created or destroyed in any chemical change, only rearranged ◦ Law of ____________ __ ____

8.  Every compound is composed of atoms of different elements, combined in a specific ratio

9.  Discovered that atoms had negatively charged particles and reasoned that the atom had to contain positively charged particles because the atom is electrically neutral 

10.  Inferred that an atom’s positive charge must be clustered in a tiny region in its center called a nucleus

11.  Electrons moved around the nucleus  He also named protons

12.  Theory came from Gold foil experiment. (see figure 4 & 5, pages 104 & 105)  some of the alpha particles had run into massive concentrations of positive charge and, since like charges repel, had been hurled straight back by them

13.  Showed that electrons could only have specific amounts of energy, leading them to move in certain orbits around the nucleus

14.  Electrons do not orbit the nucleus like planets, but can be anywhere in a cloud like region around the nucleus

15.  An electron’s movement is related to its energy level.  The specific amount of energy the electron has  Electrons of different energy levels are found in different places.

16.  James Chadwick discovered the neutrons, which are found in the nucleus, they have no charge and almost as much mass as the protons

17.  The model consists of an atom made up of a nucleus which contains the protons and neutrons surrounded by a cloudlike region of moving electrons contained in energy levels

18.  Protons are shown by a plus sign(1+), AMU = 1

19.  Electrons are shown by a minus sign(1-),  AMU = 1/ 1, 836

20. ◦ Neutrons are shown by a zero sign(0), ◦ AMU = 1

21.  Every atom of an element has the same number of protons

22.  The atomic number identifies the element

23.  Since an element is electrically neutral, the atomic number also equals the number of electrons.

24.  The number of neutrons in an atom can vary.

25. ◦ Atoms with the same number of protons but different numbers of neutrons are called isotopes. ◦ Figure 10, page 108

26.  An isotope is identified by its mass number

27.  The sum of protons and neutrons in the nucleus

28. ◦ Number of neutrons can be found by subtracting the atomic number FROM the Mass number.  Mass number minus Atomic number = Neutron number