How Much? & Rates and Energy Flashcards
Protons and neutrons have the same…
Mass
Mass of atoms, relative masses of proton and neutrons
1
Mass number
Total number of protons and neutrons in an atom
Why do we count only protons and neutrons to calculate the mass number of an atom?
As the mass of an electron is very small so the mass of an atom is made of it’s protons and neutrons
Atoms of the same element all have the same
Atomic number
Would should always be the same amount in an atom
Protons and electrons
Isotopes
Atoms of the same element with different numbers of neutrons
Mass number?
Top number on symbol
Atomic number
Bottom number
Neutrons how can you find the amount
Mass number - atomic number = neutrons in atom
How many protons, electrons, neutrons in an atom of 19 (top) F 9 (bottom)
Protons and electrons = 9 neutrons = 10
Relative atomic masses ( A r)
What we use to weigh atoms as too small
Relative atomic mass of an element is an ..
Average value
Real stove formula mass (M r) is found by
Adding up relative atomic masses of the atoms in it’s formula
Calculate the M r of calcium chloride CaCl2
A r of Ca = 40 A r of CI = 35.5
So M r = 40 + (35.5 multiplied by 2) = 111
What is the mass of one mole of sodium hydroxide NaOH
A r of Na = 23 A r of O = 16 A r of H = 1 so 1 mole NaOH = (23+16+1)g = 40g
Percentages how do you work them out
Relative atomic masses multiplied by relative formula mass answer multiplied by 100 = percentage
What is the percentage of carbon in carbon dioxide? CO2 carbon =12 O = 16
C= 12 O=16
M r of CO2 = 12 + (2 multiplied by 16) = 44
Percentage of carbon = (12/44) multiplied by 100= 27.3%