CH1 - Basic ideas about atoms

Proton has the mass of 1 and charge of +1

Neutron has the mass of 1 and charge of 0

Electron has a negligible mass (1/1840) and a charge of -1

It forms a positive ion/cation.

It forms a negative ion/anion.

Where unstable isotopes split up to form smaller atoms. This happens as the nucleus divides and sometimes protons, neutrons and electrons fly out. The element is said to be radioactive.

Alpha particles consist of two protons and two neutrons, therefore helium nuclei

They are the least penetrating of the three types of radiation and are stopped by a thin sheet of paper or even a few cm of air

They are positively charged

High-energy electrons that are more penetrating than alpha radiation

They can travel through up to 1m of air, but they're stopped by a 5mm thick sheet of aluminium

They are negatively charged

High-energy electromagnetic waves which are the most penetrating type of radiation

They can pass through several cm of lead or more than a metre of concrete

They have no charge

Gamma rays are undeflected

Alpha particles are deflected towards the negative charge, proving positive

Beta particles are deflected towards the positive charge, proving negative

When a charged particle cuts through a magnetic field it experiences a force referred to as the motor effect.

Alpha particles are deflected towards the negative charge, proving positive

Beta particles are deflected towards the positive charge, proving negative

Gamma rays are unaffected by the magnetic field, showing they have no charge

Its mass number decreases by 4 and its atomic number decreases by 2

The product is two places to the left in the periodic table

Its mass number is unchanged and its atomic number increases by 1

The product is one place to the right in the periodic table

It's a process of inverse beta decay, atomic number decreases by 1

Product is one place to the left in the periodic table

e.g X + e- > X

Atomic number decreases by 1

Product is one place to the left in the periodic table

e.g X > X  + B+

Damages the DNA, leading to mutations and possibly the formation of cancerous cells. 

Gamma radiation is the most dangerous outside of the body, but inside the body alpha is more dangerous.

Cobalt-60 is used in radiotherapy for cancer treatment. High energy gamma rays kill cancer cells, preventing malignant tumours from forming.

Technetium-99m is used as a medical radioisotope. It's used as a tracer to label a molecule which is taken up by the tissue to be studied.

Carbon-14 is used to calculate the age of plant and animal remains

Potassium-40 is used to estimate the geological age of rocks

Dilution analysis in the use of isotopically labelled substances to find the mass of a substance in a mixture

Measuring the thickness of metal strips or foils

S subshell which can hold 2 electrons

P subshell which can hold 6 electrons

D subshell which can hold 10 electrons

F subshell which can hold 14 electrons

1) Electrons fill atomic orbitals in order of increasing energy (Aufbau principle)

2) A max of 2 electrons can occupy any orbitial each with opposite spins (Pauli exclusion principle)

3) The orbitals will first fill with 1 electron each with parallel spins, before a second is added with a paired spin (Hund's rule)

First: X(g) > X+(g) + e-

Second: X+(g) > X2+(g) + e-

Third: X2+(g) > X3+(g) + e-

etc

Size of positive nuclear charge - greater charge, greater attractive force on outer electron, greater the ionisation energy

Distance of outer electron from nucleus - force of attraction between the nucleus and outer electron decreases as the distance between them increases, the further an electron from the nucleus, the lower the ionisation energy

Shielding effect - electrons repel each other as they're negatively charged, electrons in filled inner shells repel electrons in outer shells, reducing effect of positive nuclear charge, more filled inner shells, smaller attractive force on outer electron, lower the ionisation energy

c = fλ (c = speed of light)

E = hf (h is Planck's constant)

f ∝ E

If frequency increases, energy increases.

f = 1/λ

If frequency inceeases, wavelength decreases

When white light is passed through the vapour of an element, certain wavelengths are absorbed by the atoms and removed from the light.

When you look through a spectrometer, black lines in the spectrum show where light of some wavelengths has been absorbed.

Wavelengths correspond to the energy taken in by the atoms to promote them to higher energy levels.

When atoms are given energy the electrons become excited, and the energy promotes them to higher energy levels

When the energy is removed, the electrons leave the excited state and fall from the higher energy level, releasing the energy as a photon with a specific frequency 

This is shown as coloured lines on a black back ground

One electron, simplest emission spectrum. 

Atom excited by energy, electron jumps to a higher energy level. When it falls back down it emits energy as a photon, and it can be seen as a line in the spectrum.

Each line in the Lyman series is due to an electron returning to n=1, while the Balmer series is due to electrons returning to n=2.

Spectral lines become closer together as frequency increases until they converge to a limit

Convergence limit corresponds to the point at which the energy of an electron is no longer quantised and the nucleus has lost control over the electron, the atom is ionised

Lyman series n = 1, convergence limit represents the ionisation of the hydrogen atom. 

ΔE = hf

Δ x Avogadro's constant = 1st I.E for a mole of atoms