1. Atoms and Molecules

2. Protons, Neutrons and Electrons
Found in
Charge
# of each
Type of element
nucleus
nucleus
Orbiting the nucleus +1
neutral -1
Same as electrons
Can vary
Same as protons
Determines atomic number
Proton
Neutron
Electron

3. What’s wrong with this atom?
Proton
Neutron
Electron
Too many neutrons
# of particles in nucleus is the same as the electron #
Too many electrons
Too many protons

4. What element is this? Helium Carbon Oxygen
Proton
Neutron
Electron
Helium
Carbon
Oxygen
Not enough information to determine

5. What element is this?
Carbon
Beryllium
Magnesium

6. Isotopes
The atomic number tells you the number of protons in the nucleus
Each type of atom has a different atomic number and is a different element
As of 2011, there are 118 elements.
While the proton # determines the element, each element can have varying #’s of neutrons. These are called isotopes

7. Examples of Isotopes

8. Examples of Isotopes

9. Chemical Bonds
Electrons are organized into layers called shells surrounding the nucleus
The first shell can hold 2 electrons, the second shell can hold 8, and all additional shells can hold 8 electrons in the outer shell
Atoms that have 8 electrons in their outer shell are stable and normally do not form bonds
Atoms that do not have 8 electrons in their outer shell will form chemical bonds with other atoms to fill their outer shell and become stable

10. Examples of Stable Atoms

11. Ionic Bonds
An atom may steal an electron from another to fill its outer shell.
The atom that loses the electron also ends up with a full outer shell
The atom that stole the electon now has more electrons than protons and becomes a negatively charged ion
The atom that lost the electron now has more protons than electrons and becomes a positively charged ion
Both atoms are attracted and bond to each other because of their opposite charges

12. Examples of Ionic Bonds

13. Examples of Ionic Bonds

14. Covalent Bonds
Two atoms may share electrons in their outer in order to fill their outer shell - remember: electrons in the first shell and in all others

15. Examples of Covalent Bonds
Hydrogen now has a full outer shell: 2 electrons
Chlorine now has a full outer shell: 8 electrons

16. Water forms through covalent bonds
Hydrogen has one electron in its outer shell.
How many more does it need to be stable?
Oxygen has 6 electrons in its outer shell.
How many more does it need to be stable?
How many hydrogen atoms does oxygen need to share with to fill its outer shell?