Chemistry - Atomic structure

What is the relative mass, charge and position of a proton?

relative mass of 1, relative charge +1 and position inside the nucleus.

What is the relative mass, charge and position of a neutron?

relative mass of 1, relative charge 0 and position inside the nucleus.

what is the relative mass, charge and position of an electron?

relative mass of 1/2000, charge of -1 and position orbitals.

what is the atomic number (Z)?

the number of protons in an element.

what is the mass number (A)

the sum of protons and neutrons inside the nucleus?

what are isotopes?

isotopes are atoms of an element with the same number of protons but a different number of neutrons.

why do isotopes have similar chemical properties?

As they have the same electron configuration.

do isotopes have the same physical properties?

no, they have varying physical properties due to their difference in mass.

what can a TOF mass spectrometer be used for?

it can be used to identify all the isotopes present in a sample of an element and therefore predict the element.

what are the steps in TOF mass spectrometry?

1. vaporisation
2. ionisation
3. acceleration
4. separation
5. detection

What are the two methods of ionisation?

electron impact ionisation and electrospray ionisation.

what is electron impact ionisation?

This method is used for low Mr. elements as it could fragment larger ones. An electron gun fires high energy electrons to the sample knocking off an electron forming a positive ion.

what is electrospray ionisation?

This method is used for larger molecules. The sample is dissolved in a volatile solvent and is put through a fine needle that has a high voltage at the tip this causes the atoms to gain a proton and become positive ions. the solvent evaporates as the ions are accelerated.

What happens in acceleration stage of TOF mass spectrometery?

Positive ions are accelerated by an electrostatic field as they are attracted to the negatively charged plate to a constant kinetic energy.

What determines an ions velocity in the acceleration area?

Its mass. Lighter particles have a faster velocity, and heavier particles have a lower velocity.

What happens in the detection stage of TOF Mass spectrometery?

The ions reach the detector gain an electron which produces a current, the size of this current is proportional to the abundance of the species.

What is electron configuration?

The arrangement of electrons in an atom.

How are electrons arranged in an atom?

Electrons are arranged on:
Principle energy levels numbered 1,2,3,4 (1 is closest to the nucleus) split into..
Sub shells S, P, D, F split into..
Orbitals which can hold up to 2 electrons of opposite spin.

How many electrons can fit into each subshell?

s holds up to two electrons
p holds up to six electrons
d holds up to 10 electrons
f holds up to 14 electrons

What are orbitals?

Clouds of negative charge in which electrons are in.

What are the different types of orbitals?

S - orbital
P - orbital
D - orbital
F - orbital

What is the shape of the S - orbital?

spherical.

What is the shape of the P - orbital?

Dumbbell.

How does an atom fill its subshells?

In order of increasing energy.
1s, 2s, 2p, 3s, 3p, 4s, 3d. (Note: 3d is higher in energy than 4s so gets filled in after it)

What is first ionisation energy?

The enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions.

what is the first ionisation energy symbol?

H -> H+ + e-

What is the second ionisation energy?

The enthalpy changes when one mole gaseous ions with a single positive charge forms gaseous ions with a double positive charge.

What are the three factors that affect ionisation energy?

1. the attraction of the nucleus
2. the distance of the electrons from the nucleus
3. shielding of the attraction of the nucleus.

When do successive ionisation occur?

When further electrons are removed.

What happens to ionisation energies along a period?

First ionisation energy increases due to decreasing atomic radius and greater electrostatic force of attraction.

What happens to ionisation energy down a group?

First ionisation energy decreases due to increasing atomic radius and shielding which weakens electrostatic force of attraction.

Why are successive ionisation energies often larger?

The second ionisation energy of an element is always larger as when the first electron is removed a positive ion is formed, the ion increases the attraction on the remaining electrons, so that the energy to remove the next is larger.

Why does helium have the largest first ionisation energy?

Its first electron is closest to the nucleus and experiences no shielding.

Why does Na have a lower ionisation energy than Ne.

This is because Na will have its outer electron in a 3s shell further from
the nucleus and is more shielded. So, Na’s outer electron is easier to
remove and has a lower ionisation energy.

Why is there a small drop from Mg to Al?

Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s
sub shell. The electrons in the 3p subshell are slightly easier to remove because
the 3p electrons are higher in energy and are also slightly shielded by the 3s
electrons

Why is there a small drop from P to S?

With sulfur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill
the first 3p orbital.
When the second electron is added to a 3p orbital there is a slight repulsion between
the two negatively charged electrons which makes the second electron easier to
remove.