Studied by 7 peopleTags & Description
what was stated in Dalton's atomic theory?
atoms are tiny particles made of elements
atoms cannot be divided
all atoms in an element are the same
atoms of one element are different to those of other elements
what did Thompson discover about electrons?
they have a negative charge
they can be deflected by magnet and electric field
they have very small mass
explain the plum pudding model
atoms are made up of negative electrons moving around in a sea of positive charge
what were Rutherford's proposals after the gold leaf experiment?
most of the mass and positive charge of the atom are in the nucleus
electrons orbit the nucleus
most of atom's volume is the space between the nucleus and the electrons
overall positive and negative charges must balance
explain the current model of the atom
protons and neutrons are found in the nucleus
electrons orbit in shells
nucleus is tiny compared to the total volume of the atom
most of atom's mass is in the nucleus and the electron
what is ther charges of sub-atomic particles?
proton = +1
electron = -1
neutron = 0
what particle has the same mass as a proton?
neutron
which 2 particles make up most of the atom's mass?
protons and neutrons
what letter is used to represent the atomic number of an atom?
Z
what does the atomic number tell us about an element?
atomic number = number of protons in atom
which letter represents mass number?
A
how is mass number calculated?
mass number = number of protons + number of neutrons
how would we calculate number of neutrons?
number of neutrons = mass number - atomic number
define isotope
atoms of the same element with different numbers of neutrons
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
what are ions?
charged particles formed when an atom loses or gain electrons
what is the charge of the ion when electrons are gained?
negative
what is the unit used to measure atomic mass
unified atomic mass unit, u
define relative atomic mass
the weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12
what is the unit of relative atomic mass
no units
define relative isotopic mass
the mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12
relative atomic mass is the same as which number?
mass number
what 2 assumptions are made when calculating mass number?
contributuion of the electron is neglected
mass of both proton and neutron is taken as 1.0 u
how to calculate relative molecular mass and relative formula mass?
both can be calculated by adding the relative atomic masses of each of the the atoms making up the molecule or the formula
what are the uses of mass spectrometry?
identify unknown compounds
find relative sbundance of each isotope of an element
determine structural information
how does a mass spectrometer work?
the sample is made into positive ions
they pass through the apparatus and are separated according to mass to charge ratio
a computer analyses the data and produces mass spectrum
how is the group number related to the number of electrons?
group number = number of electrons in outer shell
is the group number indicated by the horizontal row or verticle column in the periodic table
verticle column
do metals usually gain of lose electrons?
lose electrons to form positive ions
which 4 elements don't tend to form ions and why?
beryllium
boron
carbon
silicon
it requires a lot of energy to transfer outer shell electrons
what are molecular ions?
covalently bonded atoms that lose or gain electrons
what's the charge of an ammonium ion?
+1
NH₄⁺
what is the charge of a hydroxide ion?
-1
OH⁻
what is the charge of a nitrate ion?
-1
NO₃⁻
what is the charge of a carbonate ion?
-2
CO₃²⁻
hat is the charge of a sulfate ion?
-2
SO₄²⁻
what is emperical formula?
simplest whole number ratio of atoms of each element present in a compound
how to calculate emperical formula?
divide the amount of each element by its molar mass
divide the answers by the smallest value obtained
if there is a decimal, divide by a suitable number to make it into a whole number
Note
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