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2.1.2a atomic structure_table_and_octet_rule

The document discusses the properties of the first 20 elements in the periodic table. It summarizes that the atomic number determines the element by specifying the number of protons. It also notes that the atomic mass is about twice the atomic number due to neutrons, and that electrons fill electron shells from the inside out, with most elements following the octet rule of filling the outer shell with 8 electrons to achieve stability.

Education◦
2.1.2 The first twenty Elements in the Periodic Table
• Let us revise the atomic structure of these elements by drawing a table in the back of our practical books • List them • Give their atomic number • Then their atomic mass • Then their numbers of protons • Then their numbers of neutrons • Then their numbers of electrons • The finally their electron patterns
Atomic Element Number Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Fosforus Sulphur Chlorine Argon Potassium Calcium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
• Next comes the atomic mass • Compare the atomic mass number to the atomic number • Is there a pattern? • In many tables there are decimal points – ignore these
Atomic Atomic Element Number Mass Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorous Sulphur Chlorine Argon Potassium Calcium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 39 40
What did you notice? • Atomic mass gets bigger as the atomic number increases – as a general rule • The atomic mass is roughly twice the atomic number
Atomic Atomic Element Number Mass Proton Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorous Sulphur Chlorine Argon Potassium Calcium 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 39 40
What did you notice? • The number of protons equals the atomic number • It is the atomic number that determines what the element is. • If the atomic number changes then the element becomes a different element
Atomic Atomic Element Number Mass Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorous Sulphur Chlorine Argon Potassium Calcium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 39 40 Proton Neutron Number Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 2 4 5 6 6 7 8 10 10 12 12 14 14 16 16 18 22 20 20
What did you notice? • The number of neutrons is the atomic mass minus the atomic number • The number of neutrons is roughly the same as the number of protons
Atomic Atomic Element Number Mass Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorous Sulphur Chlorine Argon Potassium Calcium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 39 40 Proton Neutron Electron Number Number Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 2 4 5 6 6 7 8 10 10 12 12 14 14 16 16 18 22 20 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
What did you notice? • Number of electrons is equal to the number of protons • This is why atoms are neutral [positive protons and negative electrons cancel out • The number of electrons is also equal to the atomic number
Atomic Atomic Element Number Mass Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorous Sulphur Chlorine Argon Potassium Calcium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 39 40 Proton Neutron Electron Electron Pattern Number Number Number K L M N 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 2 4 5 6 6 7 8 10 10 12 12 14 14 16 16 18 22 20 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 3 4 5 6 7 8 8 8 8 8 8 8 8 8 8 8 1 2 3 4 5 6 7 8 8 8 1 2
What did you notice? • Shells fill from centre outwards • When outer shell becomes full something different happens - shown by shading • Atoms become very stable • Octet rule because usually when there are eight electrons in outer shell • Helium is an exception
Summary
• Atomic number is a series • Atomic number tells number of protons • Number of protons determines the element • Atomic Mass is about twice atomic number • Difference caused by neutrons • Number of neutrons calculated by atomic mass – atomic number
• Number of electrons = number of protons = atomic number Electrons fill shells from inside out • 2,8,8,(2) is maximum – brackets because not full • If an outer shell is full the atom is very stable • Usually 8 electrons fill the outer shell – Octet rule • Helium is one exception