S1 - Atomic structure
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What do atoms consist of?
A central nucleus, composed of protons and neutrons, surrounded by electrons, orbiting in shells
What makes the nucleus have a positive charge? Why is almost the whole mass of the atom concentrated in the nucleus?
The protons are heavy and positively charged
Describe a neutron and electron
• Neutrons are heavy and have a neutral charge - Protons are tiny and light and have a negative charge
What is the relative mass and charge of protons, neutrons and electrons?
Proton - mass 1, charge +1 Neutron - mass 1, charge 0 Electron - mass 1/2000, charge -1
What is the atomic number?
The number of protons
Where does the mass number next to the symbol of the element?
Top left hand corner
Where does the atomic number go next to the symbol of the element?
Bottom left hand corner
What is the mass number?
The number of protons and neutrons
How do you work out the number of neutrons?
Subtract the atomic number from the mass number
Atoms of the same element all have what the same?
The number of protons
Atoms of different elements will have different what?
Number of protons
What is the relative atomic mass?
A measure of the mass of one atom of the element compared with the mass of an atom of C-12 (mass is exactly 12) - the average mass of all isotopes of an element
What two things do you need to know to work out the relative atomic mass?
Relative mass of each isotope and its relative abundance
What does the relative abundance mean?
How much there is of the each isotope compared to the total amount of the element in the world
What is the equation for working out the relative atomic mass?
(% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2) ÷ 100
What is an isotope?
Atoms that have the same number of protons and electrons but different number of neutrons • same proton number • different mass numbers
Give an example of an isotope
C-12 and C-14 (used in carbon dating)
What does the period table show?
Elements put in order of increasing atomic number
How is the period table laid out?
Elements with similar properties are put in the same column (group)
What group the elements are put into corresponds to what?
The number of electrons the elements have on their outer shell (group 1 have 1, group 2 have 2…) This is why there properties are similar
What are the five electron shell rules?
1) Electrons always occupy shells (energy levels) 2) Lowest energy levels are always filled first - closest to the nucleus 3) Only a certain number of electrons are allowed in each shell 4) Atoms are happy when they have full electron shells - like the noble gases 5) In most atoms the outer shell is not full making the atom want to react
What are the certain number of electrons allowed in each shell?
1st shell = 2 2nd shell = 8 3rd shell = 8 (still filling)
What is the electronic configuration?
The distribution of electrons in an atom
How do you work out the electronic configuration?
Use your period table and the electron shell rule (atomic number = protons and the no. of protons = no. of electrons)