1. Representing Elements and Atoms

2. What’s in an atom?  We now know the atom is made of 3 subatomic particles Protons (in the nucleus) Protons (in the nucleus) Neutrons (in the nucleus) Neutrons (in the nucleus) Electrons (orbits the nucleus) Electrons (orbits the nucleus)  We also know electrons orbit the nucleus in specific regions, at a fixed distance from the centre

3. What’s in an atom?  Each subatomic particle has its own set of properties

4. What’s in an atom?  Complete the properties chart: Name Relative Mass Electric Charge Location Proton1 Neutron1 Electron 1/1840 (~ 0.0005)

5. In the Nucleus….  Protons and neutrons contribute nearly all the mass of the atom The mass of an electron is so small it is deemed “negligible” The mass of an electron is so small it is deemed “negligible” What does negligible mean?What does negligible mean?

6. Relative Size

7. Charge  Every proton carries exactly the same amount of positive charge (+1)  Every electron carries exactly the same amount of negative charge (-1)  Every electron carries a negative charge exactly opposite that of a proton.

8. Atomic Number   The number of protons in an atom = atomic number   The atomic number identifies an atom as a specific element Eg. Atomic number 6 means this atom has 6 protons in it Only carbon has 6 protons If a proton is somehow added to this atom, it is no longer carbon - it becomes nitrogen (atomic number 7), a completely different element

9. Mass Number  Mass number = # protons + # neutrons   If I know the mass number, how can I determine the number of neutrons in an atom? # neutrons = mass number – atomic number = total # P & N – # P # neutrons in Na = 23 – 11 = 12

10. Number of Subatomic Particles   How do you find the number of electrons? In a neutral atom, positive charge = negative charge Therefore, # protons must = # electrons since they have equal, but opposite charge

11. Number of Electrons   Ex. In a neutral carbon atom, how many electrons are there? Carbon’s atomic number is 6. Therefore, there are 6 protons. Since there are 6 protons, there must also be 6 electrons to balance the charge (+6) + (-6) = 0 6 protons x (+1) charge each 6 electrons x (-1) charge each Gives you an atom with no overall charge

12. Shorthand Notation for Elements   The same way it is easier to write 5678 - instead of five thousand six hundred seventy- eight, we need a shortcut for atoms of elements   Each element has its own symbol. This is a universal ‘language’ for all scientists. Na  sodium K  potassium C  carbon

13. Shorthand Notation for Elements   The symbol is always a capital letter first Ar Ne B   Remember: Atomic number = a whole number (no decimal) Atomic mass = usually a decimal (an average of the # neutrons)

14. Isotopes  Isotopes: Atoms with the same number of protons but a different number of neutrons.  Different varieties of the same element  2 common isotopes are Carbon-14 and Carbon-12.  Both isotopes are carbon because they each have 6 protons  Both isotopes are carbon because they each have 6 protons  They are different because C-14 has 8 neutrons and C-12 only has 6  While C-12 is the most abundant (common) isotope of carbon, both are called isotopes

15. Isotopes  Here is the isotopic notation for carbon 14.  How many protons, neutrons and electrons? Protons- Carbon’s atomic number is 6, Protons- Carbon’s atomic number is 6, Therefore there are 6 protons Therefore there are 6 protons Electrons- If the atom is neutral, the number of protons = the number of electrons Electrons- If the atom is neutral, the number of protons = the number of electrons Therefore there are also 6 electrons Therefore there are also 6 electrons Neutrons- The mass number equals the number of protons + neutrons, Neutrons- The mass number equals the number of protons + neutrons, Therefore 14-6 leaves 8 neutrons Therefore 14-6 leaves 8 neutrons

16. Standard Atomic Notation   Homework: Learn the first 20 symbols Learn the first 20 element names in order (Atomic numbers 1-20) Spelling included!

17. Homework Element symbolElement name 1HHydrogen 2HeHelium 3LiLithium 4…… 5…… …etc……