IB chemistry topic 2
Terms in this set (68)
Relative atomic mass
Average mass of an atom, taking into account the relative abundances of all the naturally occurring isotopes of the element, relative to one atom of Carbon-12.
Modern atomic theory
1.All matter is composed of individual particles
2. Can't be destroyed or created
3. All atoms of a given element are identical
4. Atoms of different elements are of different sizes
5.Atoms can be combines to make molecules
Sum of protons and neutrons in an atom's nucleus. A
Total amount of protons in an atom's nucleus. Orbiting electrons are in equal number. Z
Atoms of the same element, but with differing mass number.
Portrays an unbroken sequence of frequencies. Contains all wavelengths.
Portrays various frequencies of light in terms of single lines. Produced by atoms who get their electrons excited to fall back to their normal energy levels.
White light passed through a sample, which absorbs certain wavelengths.
Wavelengths separated by a prism.
Absorbed light energy is used to excite electrons
Results in absorption spectra where wavelengths are missing.
Sample heated or at high voltage.
Emits certain wavelengths.
Results in line spectrum that contains wavelengths missing from absorption spectra.
When electron number differ from proton number, the atom carries a charge.
An atom that has less electrons than protons is positively charged.
An atom that has more electrons than protons is negatively charged.
An apparatus that can give information about isotopic composition of different elements and the structure of molecules.
A graph with % abundance plotted against mass/charge, gained as a result from the mass spectrometer.
organization of electrons in an atom by increasing energy shells.
arrangement of electromagnetic radiation--including radio waves, visible light from the Sun, gamma rays, X rays, ultraviolet waves, infrared waves, and microwaves--according to their wavelengths
the number of complete wavelengths that pass a point in a given time. v
h=6.636*1E-34 J.s. Energy is related to the frequency of the radiation by Planck's equation.
the length from one crest to another. λ
the highest point of a wave.
Lowest point of a wave.
The unstable energy of an electron, which is disposed of when the electron moves down to the ground state.
The stable energy of an electron.
Outer electrons in the outmost energy shell.
First ionization energy
The minimum energy required to remove one mole of electrons from one mole of gaseous atoms in their ground state.
The arrangement of electrons of an atom in its ground state into various orbitals around the nuclei of atoms. The number of electrons in each energy sub-level.
s, p, d, f; denotes shape of orbital
How many electrons can there be occupied in a s orbital?
State the maximum amount of electrons that can fill up a p orbital.
State the maximum amount of electrons that can up a d orbital.
State the maximum amount of electrons that can up a f orbital.
The regions around the nucleus within which the electrons have the highest probability of being found
Pauli exclusion principle
-only electrons with opposite spin can occupy the same orbital.
-any electron is uniquely identified by it's orbital and spin
States that orbitals with lower energy are filled before those with higher energy.
Hund's third rule
Principle states the following: if more than one orbital in a sub-level is available, electrons occupy different orbitals with parallel spins.
Which subatomic particles are in the nucleus
Protons and neutrons. Known as nucleons.
Has a negative charge, occupies space outside the nucleus and responsible for an atom's volume.
Mass and charge of subatomic particles.
Electron: charge= -1 mass= 5*10^-4(most often considered negligible.)
Proton: charge= +1 mass: 1
Neutron: charge=0 mass :1
How to find number of neutrons
A(mass number)-Z(atomic number)
What differs between isotopes of the same element?
They have similar physical properties such as: mass density and melting and boiling points. Because they have the same electron configuration they have the same chemical properties.
Used to describe the number of electrons in each orbital. Each orbital is represented by a box and each electron by a single-headed arrow which represents the direction of it's spin.
In which order are sub levels filled?
Condensed electron configuration
Use square brackets to show the noble gas core.
The blocks of the periodic table.
Elements in the s-block have valence electrons in the s sub-level and so on.
How can you calculate ionization energy?
Use the equation: E=hv
Trend regarding first ionization energy.
Decrease down a group-due to increasing distance of outer electrons from the nucleus.
Increase in general along a period-due to increasing effective nuclear charge.
Show regular discontinuities in the increase across a period-due to the existence of sub-shells.
What do successive ionization energies of the same element show?
Evidence for electron configuration, such as sub-levels and main-levels.
Large increases occur when an electron is removed from a different energy level. Smaller increases occur when an electron is removed from a different sub-level. A very small jump occurs when removing an unpaired electron instead of a paired one because it's slightly easier to remove a paired electron because they are repelled by their partner.
What produces the lines of an emission spectra?
Excited electrons falling from higher to lower energy levels.
model of an atom that shows electrons in circular orbits around the nucleus. "Solar system"
What is 1 amu?
The mass of 1/12 of a C12 atom
How wavelength and frequency related?
Inversely proportional. When 1 increases the other decreases. Wavelenght*frequency=the speed of light(c)
Thomson "plum pudding" model
Metals contain negatively charged particles, electrons distributed in a positive sponge
Shot alpha particles through thin gold foil
Most got through some got reflected
Nuclear atom=very small but dense positively charged nucleus
electrons orbit around central nucleus
Electrostatic forces between nucleus and electrons.
Neutrons hold nucleus together
Arrangement of elements in periodic table
By number of protons and electrons
Parallel increase in mass
Groups-similar chemical properties
Example of continuous spectrum, mixture of all visable wavelengths
Wave-particle dualism of light
Light can be described as both waves and particles
Visable light: e fall down to 2nd level
UV light: e fall down to ground level
IR light: e fall down to 3rd level
What happens to e that go to the highest energy level?
They have been completely removed
The energy needed to remove one mole of electrons from a mole of atoms in the gaseous phase.
Limitations of Bohr model
-Only usable for hydrogen
-Is a simplification
-Reality is more complicated, main levels split into sublevels
Evidence for light as waves
Difraction pattern is typical for waves
Evidence for light as particles
scattering of electrons is typical for particle stream.
Why is it impossible to know precise trajectory of an electron?
Because any attempt to measure it's position will change it's motion.
The highest energy levels converge. At convergence the difference is infinattely small