# Atoms

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## 1.10, 1.11: Sub atomic particles

Sub-atomic particles

Protons

• Relative mass: 1
• Relative charge: +1
• Mass number is the number of protons
• Number of protons is equal to number of electrons

Neutrons

• Relative mass: 1
• Relative charge: 0
• Number of neutrons = mass number - atomic number

Electrons

• Relative mass: 1/1836
• Relative charge: +1
• Number of electrons = number of protons (makes atom neutral)
• Mass is not significant in terms of total mass of atom

The relative atomic mass is worked out compared to an atom of Carbon-12

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## 1.11, 1.12: Terms

Isotopes

• Atoms of the same element
• Contain the same number of protons but different numbers of neutrons
• Because of the difference in number of neutrons, relative atomic mass differs

Mass number

• Total mass of an atom; essentially # of protons + # of neutrons
• Electrons are so light that their mass is practically nothing so they do not contribute to the relative atomic mass

Atomic number

• Relative mass of protons in an atom

Relative atomic mass

• The average value for all the isotopes of an element [compared to an atom of Carbon-12]
• To calculate this, (% of isotope 1 x mass of isotope 1) + (% of isotope 2 x mass of isotope 2) ÷ 100
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## 1.13, 1.14,1.15: Periodic table

PERIODIC TABLE OF THE ELEMENTS

• The periodic table is arranged in order of atomic number (# of protons)
• Group number = number of electrons in outer shell
• First shell holds 2 electrons
• Second one holds 8
• Third one holds 8
• Fourth one holds 36 (I think)
• From this, you can work out the electronic configuration. I.e. Oxygen has an atomic number of 6 and it's in group 6, so its configuration is 2, 4

Diatomic elements:
H
ave No Fear Of Ice Cold Butterbeer (Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine)

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