Counting Atomic Particles

1. Counting Atomic Particles Protons, Neutrons, and Electrons

2. The Modern Atomic Model Electron “Shells” Nucleus

3. The Nucleus • Each atom has a nucleus at its center. • The nucleus is too small to be seen by any known scientific instrument • The nucleus is composed of two sub-atomic particles: • Protons • Neutrons

4. Proton Facts • Protons “live” in the nucleus • Protons have a positive charge • The number of protons determines what type of element the atom is • Each type of element has a different number of protons in its nucleus • Hydrogen – 1 proton • Oxygen – 8 protons

5. Atomic Number • Elements are organized in the periodic table according to atomic number • The atomic number is the same as the number of protons in the atom • All atoms of the same type of element have the same number of protons • Atoms with different number s of protons are different types of elements 4 Be Beryllium 9.0

6. Counting Protons Atomic Number = # of Protons or # of Protons = Atomic Number

7. Neutron Facts • Neutrons “live” in the nucleus • Neutrons have no charge (They are neutral) • Neutrons add mass to the atom • Neutrons also help protons to stick together • An atom usually has a differentnumber of neutrons and protons

8. Atomic Mass • Protons and Neutrons have the same mass • mass = 1 AMU • Note: Round to nearest whole number in periodic table 4 Be Beryllium 9.0 Atomic Mass = (# of Protons) + (# of Neutrons)

9. Counting Neutrons # of Neutrons= Atomic Mass - (# of Protons) or Atomic Mass= # of Protons + # of Neutrons

10. Electrons – The 3rd Particle • Electrons are the third (and final) particle that make up the atom • Electrons “live” outside the nucleus • Electrons form a cloud around the nucleus called the electron shell.

11. Electrons have Very Little Mass • Electrons have almost no mass • They do not add to the atomic mass of the atom • Only protons and neutrons in the nucleus are counted for mass

12. Electrons Have Charge • Electrons have a negative charge of -1 • Electrons are written e- • Protons have a positive charge of +1 • Protons are written p+ • Neutrons have no charge • Neutrons are written n0

13. Counting Electrons • Atoms have an overall charge of zero • This means that the total number of protons (+1) and electrons (-1) must be equal. • Therefore: # of Protons = # of Electrons

14. Standard Atomic Notation • Write the symbol of the element • Write the mass number at the top left • Write the atomic number at the bottom left Ex Lithium 7 Li 3

15. 4 Summary Be • Atomic Number = # of Protons • Atomic Mass = (# of Protons) + (# of Neutrons) Beryllium 9.0 Periodic Table 9 Be 4 Standard Notation

16. Practice: • Warm-up Questions: • How many protons does Boron have? • What is the atomic mass of Boron (rounded to the nearest whole number)? • How many neutrons does Boron have? • How many electrons does Boron have? • First 20 Elements Worksheet • Complete Day #2 information: • Protons, Neutrons, Electrons, & Standard Notation • Questions #3, #4

17. Summary: • Atomic Number = # of Protons • Atomic Mass = (# of Protons) + (# of Neutrons) • Note: First round Atomic Mass to nearest whole number • (# of Neutrons) = Atomic Mass - (# of Protons) • Note: First round Atomic Mass to nearest whole number • (# of Electrons) = (# of Protons)