Topic 1- atomic structure & the periodic table

What’s the equation for how many electrons each shell can hold

2n² (n= what number she’ll it is the inner being 1)

orbital definition

A region around the nucleus where an electron could be found that can hold up to 2 electrons with opposite spins

What’s is an electron

A cloud of negative charge that has the shape of the orbital occupied by the electron

How many orbitals of p are there, so show many electrons

3 orbitals, holds 6 electrons

How many orbitals of d, so how many electrons

5 orbitals, 10 electrons

How many orbitals of f, so how many electrons

7 orbitals, 14 electrons

What’s a subshell

All the orbitals of the same type in the same shell e.g. 2p subshell

How does energy vary in subshells

As you move away from the nucleus, the energy of the subshells increases

3 rules for filling atomic orbitals

1) orbitals with lowest energy filled first.

2) you can have up to 2 e- in the same orbitals but they must have opposite spins.

3) if you have orbitals with the same energy, you out e- into individual orbitals before you pair them. Cus e- in the same orbital repel

What is shown in electron configurations

Subshells and not individual orbitals

Order of subshells till 4th shell

1s 2s 3s 3p 4s 3d 4p

Why is 4s before 3d

The energy of the 4s subshell is lower than in the 3d subshell.

And orbitals with the lowest energy are filled first

Why is chromium and copper exemptions to electron configuration following the 3 rules

Because the 3d subshell is more stable when full (like in Cu) or half full (like in Cr)

Cu= [Ar] 3d10 4s1

Cr= [Ar] 3d5 4s1

Shorthand electron configuration for Na (11e-j

[Ne] 3s1

Fist ionisation energy definition

Energy needed to remove one mole of electrons form one mole of atoms in their gaseous state to form one mole of 1+ ions (also in their gaseous state)

1st ionisation energy of Mg

Mg(g) → Mg+(g) + e-

Second ionisation energy definition

Energy needed to remove one mole of electrons form one mole of 1+ ions in their gaseous state to from one mole of 2+ ions (also in their gaseous state)

3 factors that affect ionisation energy

1) atomic radius- as increases, force of attraction between + nucleus and outer e- decreases.

2) charge on the nucleus- more protons, more the force of attraction between nucleus and outer e-.

3) shielding- outer shell e- are repelled by inner shells, so reduces attraction between outer e- and the nucleus

Why is there a gradual increase in successive ionisation energies

Each time you remove an outer e-, the remaining in the outer shell are pulled slightly closer to the nucleus. So greater attraction between outer e- and nucleus

2 factors why ionisation energy decreases down the group

1) going down atomic radius increases, outer e- further away from nucleus.

2) going down there’s more shielding between nucleus and outer e-.

So attraction between nucleus and outer e- decreases so 1st ionisation energy falls

Why does the 1st ionisation energy increase across a period

Nuclear charge increases, increasing attraction between nucleus and e-.

So atomic radius decreased across a period.

So outer e- more attracted to nucleus

Why is B ionisation energy less than Be

The outer electron in B is in the 1s. In Be it’s in 2p subshell. 2p has a higher energy than 2s.

So it talks less energy to remove the outer e- of B than be

What’s an isotope

Atoms with the same number of protons but different number of neutrons

What’s relative isotopic mass

The mass of one atom of an isotope compared to 1/12 the mass of one atom of C12

What’s relative atomic mass

The average mass of one atom compared to 1/12 the mass of an atom of C12

What’s relative molecular mass

The average mass of a molecule compared to 1/12 the mass of one atom of C12

Why do all isotopes of an element react the same way

They all have the same electron configuration

How do you determine the mass number and abundance of isotopes

Use a mass spectrometer

4 uses of mass spectrometers

1) space probes- so elements in other planets can be identified.

2) drug testing in sport- identify chemicals in body and identify breakdown products from drugs.

3) quality control in pharmaceutical industry.

4) radioactive dating