What did John Dalton hypothesise?
- Matter is composed of small particles called atoms
-The atom is the smallest unit of an element - Elements consist of one type of atom
- All atoms of an element are identical
-Atoms of other elements have different properties to others - Compounds are made of two or more elements
- Atoms cannot be created or destroyed, only rearranged
What did Joseph John Thompson hypothesise?
- Atoms are made of subatomic particles
- Atoms are neutral particles with an equal ratio of protons and electrons
- Plum pudding model
What did Ernest Rutherford hypothesise?
- Atoms are mostly made up of empty space
- Atoms have a positively charged nucleus orbited by negatively charged electrons.
What is an isotope?
Isotopes are atoms of the same element which have different masses.
How do isotopes compare to each other?
Isotopes have the same amount of protons, but different amounts of neutrons. This changes it physical properties (density, mass), but not its chemical properties.
How are elements arranged in the periodic table?
Elements are arranged in periods and groups.
Periods are the rows across (left & right) the table, and groups are the columns up and down the table.
What is electrostatic attraction? How is it determined?
The electromagnetic attraction of opposite charges holding atoms together.
It is determined by the directly proportional charge of the atom, and the inversely proportional distance of charges.
What is core charge?
Measure of attraction of valence electrons to their nuclei.
Define shielding.
When electrons of an atom’s inner shells prevent its valence electrons from being pulled by the nucleus.
Define nuclear charge and what does it impact?
The charge experienced by valence electrons from the nucleus. It influences the atom’s atomic radius, ionisation energy, and electronegativity.
Define atomic radius. How does it change in the periodic table.
Measure of the distance between the atom’s valence electron shell and its nucleus.
How does atomic radius change in the periodic table.
It increases down the groups due to the increased amount of electron shells which separate the valence electrons further from the nucleus. It decreases from left to right due to the increased nuclear charge pulling the valence electrons closer to the nucleus, reducing the distance between them.
Define ionisation energy and the first ionisation energy.
The amount of energy required to remove an electron from one mole of its atoms. The first ionisation energy is the amount required to remove the first electron.
How does ionization energy change in the periodic table?
The ionisation energy increases left to right due to the nuclear charge being stronger across the periods. This creates a stronger attraction between the valence electrons and the nucleus, requiring more energy to separate the bonds.
The ionisation energy decreases as you go down the groups due to a weaker nuclear charge that makes it easier for the atom to lose it valence electrons.
Define electronegativity.
The tendency of atoms to attract a bonding pair of elections towards itself. It increases left to right.
Define quantitisation
When an atom’s electrons can only be found at certain energy levels according to their respective shells.
How do electrons change their energy levels/shells?
Electrons can change this by either emitting or absorbing energy.
Contrast the electron’s ground and excited state.
Ground state - Lowest possible energy state
Excited state - Higher energy states above ground
How does energy levels correlate with an electron’s nuclear attraction?
Electrons with the strongest attraction to the nucles are the closest have the lowest energy states. Electrons can absorb energy and jump to a higher energy level.
Define absorption spectrum
The range of frequencies and wavelengths of visible light that can be absorbed by an atom. They correspond with specific energy levels that allow electrons to across them.
Define the emission spectra
It is the electromagnetic radiation that is emmited by atoms or molecules as the excited electrons transition from ground state to the excited state.
What is spectroscopy?
Study of the interaction between matter and electromagnetic radiation.
What does the flame test do?
They’re based on the ability of electrons to release absorbed energy as they move from higher to lower levels.
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What’s AAS based on?
Atomic absorption spectroscopy
It is based on the ability of electrons to absorb energy as they move from a lower to higher energy levels.
