1.1 - Atomic Structure Flashcards

1
Q

What does the atomic number tell us about an element?

A

Atomic number = number of protons in an atom

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2
Q

How is the mass number calculated/

A

Mass number = number of protons + number of nuetrons

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3
Q

Define Relative Atomic Mass (RAM)

A

Average mass of all isotopes of an element compared to 1/12 the mass of an atom of Carbon 12 (C^12).

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4
Q

What are isotopes of an element?

A

Different forms of the same element, containing the same number of protons but different numbers of neutrons. They still have the same chemical properties.

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5
Q

Which letter is used to represent the atomic number of an atom?

A

Z

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6
Q

Which letter represents mass number?

A

A

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7
Q

How many orbitals and shells do each of these contain?
a. 1s
b. 2p
c. 3s
d. 3d
e. 4s

A

a. 1s - 1 orbital, 2 electrons
b. 2p - 3 orbitals, 6 electrons
c. 3s - 1 orbital, 2 electrons
d. 3d - 5 orbitals, 10 electrons
e. 4s - 1 orbital, 2 electrons

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8
Q

Which one has a higher energy: 3d or 4s?

A

3d

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9
Q

What is an orbital?

A

A region around the nucleus that can hold up to two electrons.

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10
Q

What would be the relationship between 2 electrons in the same orbital in terms of their spin?

A

Have opposite spin as they repel each other as both are negative.

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11
Q

Explain why chromium does not fit the trend for electronic configuration?

A

It only has one electron in its 4s orbital before filling 3d

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12
Q

Explain why copper does not fit in the trend for electronic configuration?

A

It only has one electron in its 4s orbital before filling 3d

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13
Q

What are the two types of ionisation for a mass spectrometer? How do they differ?

A
  1. Electron impact: electron gun (hot wire filament with current through it emitting electrons) knocks off one electron from each particle to form 1+ molecular ions (these ions fragment).
  2. Electrospray: sample dissolved in volatile solvent (e.g. water or methanol) and injected through a fine hypodermic needle to give an aerosol. Needle attached to positive terminal of a high-voltage power supply and particles gain a proton from solvent as they leave the needle, producing XH+ ions (+1 charge and mass of Mr +1). (ions rarely fragment).
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14
Q

When would you use the different types of ionisation in a mass spec?

A

Electron impact is used for organic or inorganic molecules with a low formula mass.
Electrospray is used for substances with a higher molecular mass including biological molecules, e.g. proteins.

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15
Q

Describe how a time of flight (TOF) mass spec works.

A

Acceleration - positive ions attracted towards a negatively charged plate.
Ion Drift - ions pass through a hole in the plate, form a beam with constant kinetic energy and travel along the tube to the detector. TOF is therefore directly proportional to the square root of mass.
Detection - positive ions pick up electrons, current flows, m/z value and time of flight recorded . Largest current from most abundant ions.

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16
Q

Define 1st Ionisation Energy.

A

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.