Elements of Life Flashcards
Define mass number
The sum of protons and neutrons in an atom
Define atomic number
The number of protons in an atom
Define isotopes
An element with the same atomic number but a different mass number
Relative atomic mass is …
The weighted mass of an atom of an element relative to one-twelfth of the mean mass of an atom of the carbon-12 isotope
Relative molecular mass…
The weighted mean mass of a molecule ina compound relative to the one twelfth of the mean mass of the carbon-12 isotope.
Percentage yield formula
Experimental mass/ Theoretical mass x 100
Nuclear fusion is…
when two lighter nuclei fuse to form a heavier nucleus of a new element releasing a large amount of energy.
What is a titration?
A standard solution of a known concentration is reacted with a solution of unknown concentration to determine the property of the solution
Name the visible light region of the EM spectrum in order of decreasing wavelength and increasing frequency and energy.
Infrared , Visible , UV
How is emission spectra formed?
When particles in the chromosphere absorb energy, the electrons get excited and are promoted from their ground state to a higher energy level. The particles lose this energy and emit radiation which can be detected due to different wavelengths.
Describe what emission spectra looks like?
Black backhround, coloured lines
Describe what absorption spectra looks like?
Coloured background , black lines
How is absorption spectra formed?
Particles absorb some of the emitted radiation, so the light analysed from stars is missing certain frequencies. The absorption lines appear as black as they are missing frequencies of light as they have been absorbed.
Similarites of emission and absorption
As frequency increases, lines converge.
Both are line spectra
Differences of emission and absorption
Emission is a black background and coloured lines absorption is the opposite
Li+ -
Na+ -
K+ -
Ca 2+ -
Ba 2+ -
Cu 2+ -
Crimson
Yellow
Lilac
Brick red
Green
Blue green
speed of light =
wavelength x frequency
energy of a photon =
Planck constant x frequency
What is Bohr’s theory and what points did he make?
Explains why H+ only emits a limited number of specific frequencies.
E- in a H+ exists only in a certain definite energy level
A photon of light is emitted or absorbed when electron changes energy level
energy of a photon is equal to the difference btwn the two energy levels
E= Hv so frequency is proportional to energy
How many electrons can each sub shell hold
S = 2
P = 6
D =10
F =14
What is an orbital
A region of space with a high probability of finding an electron.
How is ionic bonding formed and properties
Formed from electrostatic attraction between positive and negative ions.
It occurs between a metal and a non metal. E- transferred to the non -metal.
Can conduct electricity when molten or aqueous because ions can move .
Can form giant ionic lattice like NaCl
Cations are…
Anions are…
Positive
Negative
How are covalent bonds formed and properties
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Formed between two nonmetals. Share electrons to create a full outer shell
It cannot conduct electricity.
low mp/bp
What are dative covalent bonds
When both of the electrons in the shared pair are supplied from a single atom
Macromolecular covalent structures are….
covalently bonded into a giant lattice structure and have a high melting point
What is metallic bonding + properties ?
A giant lattice of positively charged ions surrounded by a sea of delocalised electrons.
They have very strong electrostatic forces of attractions between the oppositely charged particles.
Malleable as layers of positive ions are able to slide over one another
Good conductors as sea of delocalised electrons are able to move and carry a flow of charge.
High mp/bp
acid + carbonate
salt + water + CO2
acid + metal
salt + hydrogen
how do group 2 metals react with water
Produces metal hydroxide + hydrogen. Reactivity increases down the group
How do group 2 metals react with oxygen
Produce oxides and reactivity increases down the group.
What do group 2 carbonates decompose into
Metal oxide and carbon dioxide
Trend in thermal decompositon of group 2 carbonates + why
They become more stable so increases as you go down this is because there is an increase in charge density meaning that the ion will have a more distorting effect on neighbouring negative ions
Solubility of group 2 carbonates
Decreases down the group
Solubulity of group 2 Hydroxides
Increases down the group
Ionisation enthalpy is …
the minimum energy required to remove one mole of an electron from one mole of its atoms in a gaseous state to form one mole of gaseous cations
Ionisation enthalpy trends in periodic table
Along a period - ionisation enthalphy increases due to an decreasing atomic radii + greater electrostatic forces of attractions
Down a group - ionisation enthalphy decreases due to an increasing atomic radii + electron shielding.
An acid is ….
a proton donor
A base is…
a proton acceptor
