Analysis of the Earth and Environment Lecture 2: Periodic table Flashcards
Define and explain what an isotope is
An atom of an element which has an irregularly high number of neutrons in its nucleus.
For example, Oxygen can exist as;
O 15 (atomic mass), 8 protons and 7 neutrons
O 16 (atomic mass) 8 protons and 8 protons
How is the atomic mass of elements affected by isotopes?
Since the number of neutrons is different in isotopes, the mass of the atom is different.
As a result the atomic mass of an element relies on how much of each isotope is present.
How do you calculate the relative atomic mass of an element?
Take the percentage of the isotope X atomic mass of that isotope.
For example,
99% O-16
1% O-15
99 X 16 = 1584
1 X 15 = 15
=1599
/100
=15.99
Describe the electronic shell capacities
The first shell/1n can hold 2 electrons.
The second shell/2n can hold 8 electrons.
The third shell/3n can hold up to eighteen. However, once this third shell gets 8 electrons, the next two electrons it receives goes to the fourth shell instead. After this, the third shell will keep filling up with electrons.
List the order of electron orbital types throughout shells
First 2 electrons - S shaped orbitals
Next 6 electrons in a shell take p shaped orbitals
Next 10 electrons in a shell take d shaped orbitals
14 electrons can go into f orbitals
How do you write the electron orbital notation of an element,
For example Sulfur
Atomic number of Sulfur is 16, therefore the number of electrons is 16
In first shell, there are only two electrons, and the first two electrons in a shell adopt the S shape orbit.
In the second shell there is 8 electrons, the first 2 in the shell adopt the S circulation, the remaining 6 electrons take up the P shape orbital.
In the third shell there is only 6 electrons (16 - (2+8) = 6), the first two adopt the S shape, while the last 4 adopt the P shape.
Conclusion:
1S², 2S² 2P⁶, 3S² 3P⁴
