Atomic Structure Flashcards by 9J Lucy Trainer

What did Democritus discover?

Atoms couldn’t be split.

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What did John Dalton discover?

Came up with theories about what made up different elements.

Determines atoms were tiny particles (like hard spheres) that couldn’t be split, which made up elements.

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What did J.J. Thompson discover?

Electrons and proved atoms could be split.

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What did Rutherford discover?

Used experimental work with students to develop nuclear model in which most of mass is concentrated in nucleus with electrons in shells orbiting the nucleus.

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What did Niels Bohr discover?

Electrons in atoms could only travel along certain shells.

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What did James Chadwick discover?

Experiment to show existence only neutrons.

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What are PEN number?

Proton, electrons and neutron numbers.

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What does a nucleus contain?

Protons + neutrons

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What surrounds the nucleus?

Orbitals

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Why do atoms have no electric charge?

Because they contain the same number of protons + electrons

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What is the atomic number?

Number of protons

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What is the mass number?

Protons + neutrons

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How to work out number of neutrons?

Mass no. - atomic no.

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What determines the types of atom?

Atomic number

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Isotopes definition

Atoms with same number of protons but different electrons

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How to work out relative atomic mass?

(Percent x mass)(percent x mass) / total percent

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What can the time of flight mass spectrometry be used for?

find abundance + mass of each isotope in an element so we can determine it’s relative atomic mass
find relative molecular mass of substances made of molecules

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What are the 4 stages of the time of flight mass spectrometry?

1) ionisation
2) acceleration
3) flight tube
4) detection

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What happens in the time of mass spectrometry?

Particles of the substance are ionised to form 1+ ions which are celebration so they all have the same kinetic energy
the time taken to travel a fixed distance is then sued to find the mass of each ion in the sample

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What are the 2 techniques on ionisation?

Electron impact (electron ionisation)
Electrospray ionisation

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What happens in electron impact?

sample vaporised
high energy electrons fired at it from electron gun
this knocks off one else torn from each particle forming 1+ ion
1+ ions attracted towards negative electric plate where they are accelerated

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What is an election gun?

A hot wire filament with a current running through it that emits electrons

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Equation for election impact

X + e- -> X+ + 2e-

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What is the electron impact technique used for?

Study These Flashcards

Used for elements + substances with low formula mass

How does electrospray ionisation work?

- sample dissolved in a volatile solvent (water/methanol etc) - this is injected through fine hypodermic needle to give fine mist (aerosol) - needle tip attached to positive terminal of high voltage power supply - particles ionised by gaining a proton from solvent as they leave needle producing XH+ ions - solvent evaporated away while XH+ ions attracted towards negative plate where they are accelerated

What is electrospray impact used for?

- substance with higher molecular mass | - known as ‘soft’ ionisation technique as fragmentation rarely takes place

Acceleration explanation

Positive ions accelerated is king electric field so they all have same kinetic energy

Kinetic energy calculation

1/2 mass x velocity squared

Kinetic energy of particles unit

Joules

Mass of particle units

Velocity of particle unit

m/s-1

Velocity equation

Square root of 2KE/m

What does velocity of each particle in time of mass spectrometry depend on?

Mass | Heavier = slower

Flight tube explanation

- positive ion travels through home in negatively charged plate into tube - time of flight depends on mass /velocity - ions set off along flight tube at same time - lighter ions travel faster + start to separate our - lightest ions ready detector first

2 Time equations

Distance / velocity of particle

What is time of flight proportional to?

square root of mass of ions

Detection explanation

- positive ions hit negatively charged electric plate - ions then discharged by gaining electrons from plate - movement of electrons generated + electric current is measured - current size gives a measure of number or ions hitting plate

What does the mass spectrum show?

The mass to charge (m/z) ratio + abundance of each ion that reached detector

Why is the mass to charge the mass of each ion?

Because all ions are produced by electrospray ionisation + most ions have a 1+ charge

How is a mass spectrum generated?

A computer using data

Relative abundance of an isotope definition

the percentage of atoms with a specific atomic mass found in a naturally occurring sample of an element.

Relative atomic mass (Ar) calculation

Mass of all isotopes/ abundance of all isotopes

Time of flight calculation 2

Mass in one mole /1000/ 6.02 x 10 to the power 23

What is avagadros number?

6.02 x 10 to the power of 23

What unit is distance?

Metres

Speed calculation

Distance/ time

Isotopes definitions

Variation of the same element with different number of neutrons but the same number of protons

Why do isotopes of the same elements have the same chemical properties?

Because they have the same number of elector shell

Why is the first ionisation energy of magnesium higher than that of sodium?

- more protons - same shielding - stronger nuclear charge

Relative atomic mass definition

the ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12.

Electron structure 1

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10

What is Pauli’s principle?

- no more than 2 electrons can occupy the same orbital | - 2 electrons in same orbital must have opposite spins

What is Aufban’s principle?

Electrons fill lower energy atomic orbitals before filling higher energy ones

What is Hund’s rule of maximum multiplicity?

- every orbital in a sub shell is singly occupied with one electron before any one orbital is doubly occupied - all electrons in singly occupied orbitals have the same spin

How is the electron structure different with Ti + Fe?

can’t get rid of 4s2

How is the electron structure different with Cr?

Electron moves from 4s2 so it becomes 4s1 3d5 due to electron pair repulsion

How is the electron structure different in Cu?

Goes from 4s2 to 4s1 3d10 because elements is more stable with full 10 orbital radius ether than full 2 orbital

How are electrons arranged?

Electron shells (energy levels) with sub shells (sub levels)

How to identify successive ionisation energy?

Bigger jump between numbers of each ionisation energy

Atomic Structure Flashcards

(59 cards)