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Atomic Structure
- Atoms
- protons
- relative charge: +1
- relative mass: 1
- relative charge: +1
- neutrons
- relative charge:0
- relative mass:1
- relative charge:0
- electrons
- relative charge: -1
- relative mas: 5.45*10^-3
- relative charge: -1
- atomic number: the number of protons in the nucleus of one atom
- mass number: the total number of protons and neutrons in the nucleus of one atom
- protons
- MASS SPECTROMETER
- purpose
- separate and identify isotopes
- identify unknown compounds
- separate and identify isotopes
- 4 main steps
- Ionization
- an "electric gun" fires a beam of
"high energy electrons" at the
sample, knocking out
electrons.POSITIVE IONS ARE
FORMED.
- X(g) + e- ------ X+ + 2e-
- an "electric gun" fires a beam of
"high energy electrons" at the
sample, knocking out
electrons.POSITIVE IONS ARE
FORMED.
- Acceleration
- an "electric field" is used to speed
up the positively charged ions.. the
ions are focused into a beam by
passing them through slits
- an "electric field" is used to speed
up the positively charged ions.. the
ions are focused into a beam by
passing them through slits
- Deflection
- a "magnetic field" is used to deflect
the ions, the smaller the mass of the
ions the more they are reflected and
vice versa
- a "magnetic field" is used to deflect
the ions, the smaller the mass of the
ions the more they are reflected and
vice versa
- Detection
- the ions collide with the
detector, creating an electric
current that is proportional
to the abundance of each ion
- the ions collide with the
detector, creating an electric
current that is proportional
to the abundance of each ion
- Ionization
- purpose
- Isotopes: atoms with the same number of protons but different number of neutrons
- IONIZATION ENERGY: The enthalpy change when an
electron is removed from the outer shell of a
gaseous atom
- TREND
- increases across a period
- Explanation: the nuclear charge
increases.. the attraction between the
nucleus and the outer electrons
increases..the electrons experience similar
shielding ( since they are in the same
energy shell)
- EXAMPLES
- Mg --- Al ( downfall)..... the outer electrons of Al
are in a 3p-orbital that is of higher energy than
3s-orbital, so less energy is required to remove
the electrons
- P---- S (downfall)..... the paired electrons in a p-orbital of S are paired so they
repel each other and so are easily removed..that is why S has a lower
ionization energy
- Mg --- Al ( downfall)..... the outer electrons of Al
are in a 3p-orbital that is of higher energy than
3s-orbital, so less energy is required to remove
the electrons
- EXAMPLES
- Explanation: the nuclear charge
increases.. the attraction between the
nucleus and the outer electrons
increases..the electrons experience similar
shielding ( since they are in the same
energy shell)
- decreases down a group
- the distance between the nucleus and the outer
electrons increases, therefore the force of attraction
between the nucleus and the outer electrons is
reduced, so less amount of energy is required to
remove the outer electrons
- the distance between the nucleus and the outer
electrons increases, therefore the force of attraction
between the nucleus and the outer electrons is
reduced, so less amount of energy is required to
remove the outer electrons
- increases across a period
- TREND
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