atomic structure

atomic number

no . of protons in an atom

mass number

no of protons and neutrons

relative atomic mass

average mass of all isotopes of an element compared to 1/12 the mass of an atom of carbon 12

isotopes

different forms of the same element, has the same number of protons but different number of neutrons ( still have the same chemical properties)

How many orbitals and electrons do these shells contain?

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

Does 3d or 4s have a higher energy?

3d

What is an orbital?

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

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

Within an orbital, the electrons spin in opposite directions. One electron spins up while the other electron spins down.

Explain why chromium does not fit the trend for electronic configuration

It only has one electron in its 4s orbital before filling 3d 1s² … 3p⁶ 4s¹ 3d⁵

Explain why copper does not for the trend for electronic configuration.

It only has one electron in its 4s orbital before filling 3d 1s² … 3p⁶ 4s¹ 3d¹⁰

one type of ionisation- electron impact for mass spectometer 

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).

one type of ionisation- electrospray for mass spectrometer 

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 the solvent as they leave the needle, producing XH+ ions (+1 charge and mass of Mr + 1). (ions rarely fragment)

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

Electron impact used for organic or inorganic molecules with a low formula mass.

Electrospray used for substances with a higher molecular mass including biological molecules, e.g. proteins

Describe how a time of flight mass spectrometer works

Acceleration - positive ions attracted towards a negatively charged plate.

Ion Drift - ions pass through hole in plate, form a beam with constant kinetic energy, travel along tube to detector. Time of flight 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

Define first ionisation energy

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

Along a Period - first ionisation energy

first ionisation energy increases due to a decreasing atomic radius and greater electrostatic forces of attraction.

Down a Group first ionisation energy

first ionisation energy decreases due to an increasing atomic radius and shielding which reduces the effect of the electrostatic forces of attraction

Successive ionisation energies occur

when further electrons are removed.

This usually requires more energy because as electrons are removed the electrostatic force of attraction between the positive nucleus and the negative outer electron increases.

More energy is therefore needed to overcome this attraction so ionisation energy increases.

three rules for writing out electron configurations

1. The lowest energy orbital is filled first

. 2. Electrons with the same spin fill up an orbital first before pairing begins.

3. No single orbital holds more than 2 electrons.