Topic 1: Atomic structure and the Periodic Table
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What was stated in Dalton’s atomic theory?
• atoms are tiny particles made of elements • atoms cannot be divided • all the atoms in an element are the same • atoms of one element are different to those of other element
What did Thompson discover about electrons?
• they have a negative charge • they can be deflected by electromagnetic fields • they have very small mass
Explain the current model of the atom
• protons and neutrons are found in the nucleus • electrons orbit the nucleus in shells • most of the atom’s mass is in the nucleus • most of the atom is empty space between the nucleus and the electrons
What is the charge for a proton and electron?
• proton is +1 - electron is -1
Which particle has the same mass as a proton?
neutron
Which 2 particles make up the majority of an atom’s mass?
protons and neutrons
What does the atomic number show about an element?
The number of protons
How is mass number calculated?
number of protons+ number of neutrons
How to calculate the number of neutrons?
number of neutrons= mass number - atomic number
Define isotope
Atoms of the same element with different number of neutrons and the same number of electrons but different mass numbers
Why do different isotopes of the same element react in the same way?
• neutrons have no impact on the chemical reactivity - reactions involve electrons, isotopes have the same number of electrons in the same arrangement
Define relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12
Define relative isotopic mass
The mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon-12
The relative isotopic mass is the same as which number?
mass number
What 2 assumptions are made when calculating mass number?
• contribution of the electron is neglected - mass of both the proton and neutron are taken as 1.0 u
How do you calculate the relative formula mass and relative molecular mass?
add the relative atomic masses of each of the atom making up the molecule or formula
What are the uses of mass spectrometry?
• identify unknown compounds • find relative abundance of each isotope of an element • determine structural information
What does the principal quantum number indicate?
The shell occupied by the electrons
What is a shell?
A group of orbitals with the same principle quantum number
How many electrons can the 1st shell hold?
2
How many electrons can the 2nd shell hold?
8
How many electrons can the 3rd shell hold?
18
How many electrons can the 4th shell hold?
32
What is an orbital?
a region around the nucleus that can hold up to 2 electrons with opposite spins