Basic Ideas about atoms

Define shells

regions of space around the nucleus where there is a high probability of finding an electron of a giving energy

Types of orbitals

s, p, d, f

How many electrons does the s orbital have and what shape is an s orbital

1 pair - 2 electrons

spherical shape

How many electrons can a p orbital hold and what shape is it

3 pairs - 6 orbitals

dumbbell shaped

How many electrons can a d orbital hold

5 pairs - 10 electrons

How many electrons can a f orbital hold?

7 pairs - 14 electrons

What is the electronic configuration of copper?

1s2 2s2 2p6 3s2 3p6 4s2 3d9

What is the electronic configuration of chromium

1s² 2s² 2p⁶ 3s² 3p⁴ 3d⁵ 4s¹

What are some rules about filling electrons

Fill from lowest to highest energy levels

Fill each orbital first before pairing them

Half arrow - pair of electrons

What is ionisation?

process of removing one or more electrons to form a positive ion

Define molar first ionisation

the energy required to remove one electron from each atom in one mole of its gaseous atoms.

Define successive ionisation energy?

measure of the energy needed to remove one electron in turn until all the electrons are removed from an atom E

Example of successive ionisation energy

X(g) --> X+(g) + e-

Successive ionisation energies always increase because:

there is a ________ effective nuclear charge as the same number of protons are holding _______ and _______ electrons.

As each electron is removed, there is less ________ to ________ repulsion and each shell will be drawn in slightly ________ to the nucleus.

As the distance of each electron from the nucleus _________, the nuclear ____________ increases.

greater, fewer, fewer,

electron electron closer

decreases, attraction

What factors affect ionisation energy?

The attraction if the nucleus

The distance of the electrons from the nucleus

Shielding of the attraction of the nucleus

How does attraction of the nucleus affect ionisation energy

the more protons in the nucleus, the greater the attraction

How does distance of the electrons from the nucleus affect ionisation energy?

The bigger the atom the further the outer electrons are from the nucleus therefore the attraction to the nucleus is weaker

How does shielding of the attraction of the nucleus affect ionisation energy.

An electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction to the nucleus/

Trends of ionisation energy across a period:

Ionisation energy ___________ across a period

There is an increase in ________ _________ which leads to an increase in attraction between ___________ and ____________ electrons.

As you go across a period there is _______________ change to the electron shielding as each new electron is added to a sub shell in the ________ energy level.

increases

nuclear charge

nucleus outermost

no significant same

Trend down a group:

Ionisation energy ___________ down a group.

As you go down a group there is an __________ in number of shells being filled within an atom, so the outermost electrons become further away from the _________.

The outermost electrons experience __________ ____________ and their attraction to the nucleus is ______________.

Shielding ___________ any increase in nuclear charge.

decreases

increase nucleus

increased shielding

weakened

outweighs

On a successive ionisation energy graph, what causes a jump?

A difference in energy levels such as 3s1 and 2p6

Successive Ionisation graphs start from the highest energy level

Between energy levels there is a steady but slight jump

Define the atomic spectrum

spectrum of frequencies of EM radiation emitted or absorbed during transitions of electrons between energy levels within an atom.

What are the two types of spectra

Absorption

Emission

What does an absorption spectra show?

An electron jumping from its ground state to its excited state under UV light

What do the black lines show on the absorption spectra?

show where light of some wavelengths have been absorbed

The wavelengths of these lines correspond to ________ taken in by atoms to promote ________ from lower to________ energy levels.

energy

electrons

higher

How are lines in the atomic absorption spectrum are formed?

• Vapour of element

• White light passed through vapour

  • Black lines appear where light of some wavelengths has been absorbed.

Define wavelength?

distance between two wave crests

Define amplitude of a wave?

height of a wave from baseline to crest.

Define frequency of a wave?

number of wave crests that pass through

What is c (speed of light )

f λ

What is f?

c/ λ

Therefore if frequency is ___________, the wavelength ___________.

increased

decreases

f is ________ proportional to λ

inversely

How are frequency and EM radiation are related?

E= hc/λ where h is Plank’s constant

Therefore if frequency is ____________, the energy also increases

increased

How do lines in atomic emission spectrum are formed?

• Lines represent energy emitted as a photon of light

  • when electron that has been excited to a higher energy level drops back to a lower energy level.

What does the hydrogen spectrum consist of?

separate series of lines mainly in the UV, visible, and infrared regions of EM spectrum

Lyman series

• UV region

  • each line is due to electrons returning to the 1st shell, n = 1 energy level.

Balmer series

Visible region

each line is due to electrons returning to the 2nd shell, n = 2 energy level.

Paschen Series

Infrared Region

Each line is due to electrons returning to the 3rd shell, n=3 energy level

Convergence Limit:

The highest frequency (or lowest wavelength) in the line ________ spectrum of an element, specifically for hydrogen. This limit corresponds to the ________ energy, the energy required to completely remove an __________ from an atom. As the electron transitions to _______ energy levels, the wavelengths of emitted photons get closer together, eventually ___________ at this limit

emission

ionisation

electron

higher

converging

When does a convergence limit occur?

When the lines will become so close together that it will be impossible to distinguish the difference of atoms

Define radioactive decay.

Some isotopes are unstable and split upto form smaller atoms. The nucleus divides and sometimes protons neutrons and electrons fly out making the element radioactive.

Types of radiation?

Alpha

Beta

Gamma

Alpha radiation

Helium nuclei

mass number decreases by 4, and atomic number decreases by 2

Beta Radiation

high speed high energy electrons

Mass number unchanged

Atomic number increases by 1

Gamma Radiation

High energy EM waves

No effect on mass or atomic number W

Which type of radiation is most penetrating but least ionising

Gamma

Which type of radiation is least penetrating but most ionising

Alpha

Beta plus positron emission

a proton is converted into a neutron while releasing a positron and an electron neutron.

atomic number of the original element decreases by one

daughter’ isotope is one place to the left in the Periodic Table) and has the same mass number.

Electron capture

one of the orbital electrons is captured by a proton leading tp the formation of a neutron and the emission of an electron neutrino.

Atomic number decreases by one

Daughter isotope is one place to left but same mass number

When radiation pass through matter they have enough to knock electrons out of atoms therefore ____________ them.

ionising

What is the effect of gamma rays on an electric field

Neutral - so are undeflected

What is the effect of alpha particles on an electrical field

positively charged - deflect towards negative

What is the effect of beta particles on an electrical field?

negatively charged - deflected towards positive

Why do beta particles deflect more than alpha particles?

Beta particles deflect more than alpha particles because beta is lighter

What is the effect of gamma radiation on a magnetic field

unaffected by magnetic field as they are neutral

What is the effect of alpha particles on a magnetic field

deflect towards negative pole as they are positive particles

What is the effect of beta particles on a magnetic field

deflect towards positive poles as they themselves are negative particles

Why do beta particles deflect more than alpha particles =?

Beta particles deflect more than alpha particles because they are lighter.

What is half life?

Half life is the time taken for half the unstable nuclei to decay

Consequences of ionising radiation for living cells:

Ionising radiation may damage the ______ of a cell

Damage to DNA may lead to changes in the way a cell ____________ which can cause ___________ and the formation of _____________ cells at lower doses of cell death at higher doses.

DNA

functions

mutations

cancerous

Uses for isotopes

Medicine

Radio-dating

Example of isotope used in medicine

Cobalt60 is used as a treatment for cancer.

Example of isotope used in radio dating.

Carbon 14 has a half life of 5730 which is used to calculate the age of plant and animal fossils.