Atoms and Reactions

Question 1

relative mass of an electron

Answer 1

1/1836

Question 2

what determines what element an atom is

Answer 2

its number of protons

Question 3

chemical and physical properties of isotopes

Answer 3

• same chemical properties (because same electrons)
• different physical properties - such as small differences in mass and density (because different number of neutrons)

Question 4

what is relative ATOMIC mass

Answer 4

the weighted average mass of an atom relative to 1/12th of the mass of a carbon-12 atom

(represents a mixture of different isotopes)

Question 5

what is relative ISOTOPIC mass

Answer 5

the mass of an isotope relative to 1/12th of a carbon-12 atom

Question 6

what is a mass spectrometer used for

Answer 6

to find the percentage abundance of the isotopes in an element

Question 7

what are the processes of mass spectrometry

Answer 7

• sample is vapourised
• sample is ionised (forms positive ions)
• ions accelerated
• depending on mass of ions they are more or less deflected
• ions detected at end

each ion produces a signal so the larger the signal, the greater the abundance

see mass spectroscopy notes

Question 8

relative molecular mass vs relative formula mass

Answer 8

They are essentially the same idea:

• Relative molecular mass is applied to chemicals that have a fixed formula in terms of the number of atoms involved, e.g. ethanol, C2H5OH, contains two carbon atoms, six hydrogen atoms and one oxygen
• Relative formula mass is applied to chemicals that use an empirical formula to represent them, e.g. calcium chloride, CaCl2, is an ionic lattice containing a ratio of 1 calcium ion : 2 chloride ions throughout the structure

they are both calculated by adding the relative atomic masses of all the component atoms

Question 9

formula and charge of hydrogen carbonate vs carbonate

Answer 9

HCO3-

CO3 2-

Question 10

formula and charge of a phosphate ion

Answer 10

PO4 3-

Question 11

how to complete an ionic equation

Answer 11

• give each molecule a state symbol
• if is aqueous, split the molecule apart (dissociate into its ions)
• get rid of the chunks that are the same both sides of the equation
• write the rest

Question 12

what are the ions that do not take part in an ionic equation called

Answer 12

spectator ions