1. Atoms

2. What are atoms? All matter is made of atoms Atoms are the smallest part of an element (1 million times smaller than the width of 1 piece of hair) Each type of atom is represented by an element

3. Atoms Each atom is different because of the number of protons it has. This is called the atomic number. Atomic mass can be found by looking at the bottom number in the box on the periodic table

4. What are the parts of an atom? There are three parts to an atom: protons, neutrons and electrons. Protons and neutrons are found in the nucleus (cluster in the center) Electrons are found outside nucleus circling around (in electron cloud)

5. What are the parts of an atom? Each proton and neutron have a mass of 1 amu (atomic mass unit), while electrons have a mass of about 0 amu (very small) Charges:  Proton = positive (+)  Neutron = neutral ( )  Electron = negative (-)

6. Atomic Mass Almost all of the mass found in an atom is located in the nucleus…why?

7. Atomic Mass Almost all of the mass found in an atom is located in the nucleus…why?  The nucleus is where all of the protons and neutrons are found.

8. Atomic Mass When calculating the atomic mass…  Atomic mass = protons + neutrons Since the # of neutrons are not on the periodic table, you calculate it by: # Neutrons = Rounded atomic mass – atomic number (# protons)

9. More on Atoms Atoms have the same number of protons and electrons, so they are neutral, or has no charge. If an atom loses or gains an electron, it is called an ion. Ion – charged particles that can either be positive or negative

10. Ions Ion – charged particles that can either be positive or negative If an atom loses an electron (-), would it be a positive or negative ion?

11. Ions Ion – charged particles that can either be positive or negative If an atom loses an electron (-), would it be a positive or negative ion?  Positive because you are taking away a negative charge so there are more protons than electrons

12. Ions Ion – charged particles that can either be positive or negative If an atom loses an electron (-), would it be a positive or negative ion?  Positive because you are taking away a negative charge so there are more protons than electrons If an atom gains an electron (-), would it be a positive or negative ion?

13. Ions Ion – charged particles that can either be positive or negative If an atom loses an electron (-), would it be a positive or negative ion?  Positive because you are taking away a negative charge so there are more protons than electrons If an atom gains an electron (-), would it be a positive or negative ion? Negative because you are adding a negative charge so there are more electrons than protons

14. Isotopes An isotope is an atom with a different number of neutrons.  Every atom has at least 2 isotopes  Since each isotope has a different # of neutrons, each have a different atomic mass Example: Normally, H has 1 proton, 0 neutrons Deuterium is H with 1 proton and 1 neutron Tritium is H with 1 proton and 2 neutrons

15. Electron Clouds The electron cloud is the area surrounding the nucleus (protons and neutrons) where the electrons move around Electrons arranged into energy levels called shells When the shell is full, it is complete

16. Electron configuration The farther away from the nucleus, the more energy the electrons have. How these electrons are arranged is called the electron configuration

17. Electron configuration So, how are the electrons arranged? K shell – closest to nucleus (2 electrons) L shell – more energy (up to 8 electrons) M shell – (up to 8 or 18 electrons) N shell – (up to 18 or 32 electrons)

18. Electron Configuration Example: Sodium (Na) has an electron configuration of 2-8-1. What does that mean? 2 electrons in K shell

19. Electron Configuration Example: Sodium (Na) has an electron configuration of 2-8-1. What does that mean? 2 electrons in K shell 8 electrons in L shell

20. Electron Configuration Example: Sodium (Na) has an electron configuration of 2-8-1. What does that mean? 2 electrons in K shell 8 electrons in L shell 1 electron in M shell

21. Valence electrons What about that lonely electron in the M shell in sodium? That electron is a valence electron. It is the electron in the last shell (farthest away from the nucleus). These are the electrons that form chemical bonds with other atoms and give elements their chemical properties