Structure of an atom

What are atoms made of…? https://www.youtube.com/watch?v=_lNF3_30l UE

Negligible (very small) Structure of an Atom Atoms consist of three smaller subatomic particles call the proton, neutron and electron Subatomic particle Location Mass Charge Proton  Nucleus 1 amu  + Neutron Nucleus 1 amu No charge Electron  In orbit Negligible (very small) -

Structure of an Atom Each element has a different number of protons, neutrons and electrons which gives it unique physical and chemical properties Atomic Number = # of protons Mass Number = # of protons + # of neutrons = all the heavy particles (the nucleus)

# neutrons = mass # - atomic # Therefore to determine the number of neutrons we can use the following equation: # neutrons = mass # - atomic # (protons + (protons) neutrons)

Standard Atomic Notation 39 ---------> mass # (larger number) K -------> chemical symbol 19 ----------> atomic # (smaller number) Therefore a potassium atom contains: _____ protons (atomic number) _____ electrons (same as # of protons) _____ neutrons (mass number – atomic number) 19 19 20

Question Write the atomic notation for the following: An atom of nitrogen with 7 protons and 8 neutrons 15 N 7 An atom of bromine with 35 protons and 36 neutrons 71 Br 35

Fill in the following table:   Symbol Atomic Number Mass Number Number of Protons Number of Neutrons Number of electrons Br O Li 21 59 27 65 201 121 17

Answers:   Symbol Atomic Number Mass Number Number of Protons Number of Neutrons Number of electrons Br 35  80 35 45 O 8  16 8 Li 3 7 4  Sc 21 45  24  Co 27  59 27  32  27  Zn  30 65 30  Hg  80 201 80  121  Cl  17 17 18

Isotopes Isotopes are two or more forms of an element with the same # of protons and different # of neutrons. Isotopes of an element have the same chemical and physical properties. All atomic masses listed on the periodic table are averages taken from the percent abundance of each isotope of an element

Chlorine has two common Isotopes Cl-35 and Cl-37 Mass # Atomic # Protons Neutrons Electrons Cl-35   Cl-37

Chlorine has two common Isotopes Cl-35 and Cl-37 Mass # Atomic # Protons Neutrons Electrons Cl-35  35 17  17  18 Cl-37  37  20

Example For each of the following isotopes, calculate the number of protons, neutrons and electrons C- 12 and C – 13 b) Ne – 20, Ne-21, Ne-22

Example For each of the following isotopes, calculate the number of protons, neutrons and electrons C- 12 and C – 13 C-12: 6p+, 6n, 6e- C-13: 6p+, 7n, 6e- Ne – 20, Ne-21, Ne-22 Ne-20: 10p+, 10n, 10e- Ne-21: 10p+, 11n, 10e- Ne-22: 10p+, 12n, 10e-

Bohr – Rutherford Diagrams Bohr and Rutherford discovered that the electrons of an atom are arranged in energy shells or orbits around the nucleus. Each orbit has a maximum number of electrons that it can hold. Bohr-Rutherford diagrams may be used to create visual representations of atoms Shell Maximum # of e- 1 2 8 3 4 18

Bohr Rutherford Diagrams Draw a circle to represent a nucleus.   2. In this circle write the number of protons and number of neutrons. Include the letter “P” next to the number of protons and “N” next to the number of neutrons. Also write the element symbol. 3. In circles around the nucleus, which represent the electron shells or orbitals, draw one dot for each electron in the atom. Electrons should be drawn in pairs except for electrons in the first shell. 4. Once one orbital has reached its ‘full’ capacity, move onto the next orbital until all electrons are accounted for.

Example 23 Na 11

Practice Draw B-R diagrams for: Mg B F H

To Do / For Homework Read the textbook pages 245-249 Complete the Worksheets Atomic Structure Worksheet Bohr-Rutherford Diagrams Worksheet