Chapter 2
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What subatomic particles are in the nucleus of an atom?
1) protons 2) neutrons
How are electrons arranged?
Around the nucleus in shells
What is the mass of an electron?
1/1836th the mass of a proton
What is the mass of a proton + neutron?
1
Where is most of the mass of an atom?
In the nucleus
What is the overall charge of an atom?
1) zero 2) neutral
How does the periodic table list elements?
In order of protons in the nucleus
What is atomic number, A?
Number of protons
What are isotopes?
Atoms of the same element with different numbers of neutrons + different masses
What is mass number, Z?
Number of protons + number of neutrons
How does the number of neutrons affect the reactions of an element?
They have no effect
What is an ion?
1) charged atom 2) number of electrons different to number of protons
What are cations?
1) atoms with fewer electrons than protons 2) overall positive charge
What are anions?
1) atoms with more electrons than protons 2) overall negative charge
What is the mass of a carbon-12 isotope?
12 atomic mass units (12u)
What is relative isotopic mass?
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
What is relative atomic mass?
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12
What does weighted mean mass take into account?
1) percentage abundance of each isotope 2) relative atomic mass of each isotope
How can you find the percentage abundance of the isotopes in a sample of an element?
Mass spectometry
What is the method of mass spectometry?
1) sample placed in mass spectrometer 2) sample vaporised + ionised to form positive ions 3) ions accelerated. heavier ions move slower + more difficult to deflect than lighter ions - ions of each isotope separated 4) ions detected on mass spectrum as mass-to-charge ratio - greater the abundance, larger the signal
mass-to-charge ratio (m/z) =
relative mass of ion / relative charge of ion
What type of ions do atoms of metals on the left of the periodic table form?
cations
What type of ions do atoms of non-metals on the right of the periodic table form?
anions
What is a binary compound?
A compound containing 2 elements only