Important people and terms, and other info
Terms
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- Alchemists
- Ancient chemists, whose ideas were based on pure thouht, rather than on experiments. Their goal was the separation of metals from ores. They gave a good deal of practical chemical knowledge (especially Arab and European chemists)
- Aristotle
- rejected the idea of Democritus, that the difference between substances was the result of the difference in size an shape of tiny, ubcountable particles. Aristotle proposed that matter was composed of four major elements in various proportions (water, air, fire, earth)
- atomic number
- the number of protons in an atom.
- Becquerel
- A French phicicist, Nobel laureate, and one of the discoverers of radioactivity
- Bohr
- Proposed that the electrons in an atom are restricted to having certain specific energies and are restricted to following specific paths called "orbits" at a fixed distance from the nucleus.His model, however, could not be made to work for any atom having more than one electron.
- Chadwick
- Worked with Rutherford. Discovered the neutron.
- Curie
- Pioneers of radiology. Did research on the radiation phenomena, discovered by Becquerel. Discovered nuclear energy.
- Dalton
- Developed his atomic theory, described in the laws, based on his hypotheses: the law of definite proportions; the law of multiple proportions; the law of the conservation of mass.
- Democritus
- Made the earliest model of the atom. Stated, that the differences between substances are the direct result of differences in the size and shape of tiny, uniform, uncountable particles.
- electron
- small, nagatively charged particle in an atom, that is located outside the nicleus.
- isoelectronic
- two or more atoms, molecules or ions, having the same number of electrons and the same structure (number and connectivity of atoms), ragardless of the nature of the elements involved.
- isotopes
- The atoms that have the same atomic number, but different number of neutrons (therefore, different atomic masses).
- mass number
- the mass of all the particles in an atom's nicleus.
- neutron
- a particle in an atom's nucleus, neutrally charged.
- proton
- a particle in an atom's nucleus, that is positively charged.
- Rutherford
- Performed the Gold Foil Experiment, by which he proved that the atom is mostly empty space, but contains a dence, positively charged nicleus.
- Thomson
- Discovered the existence of electrons. In his model of the atom, positive and negative charges were distributed randomly throughout the ball ("The Plum Pudding model")
- Valence electrons
- Electrons which can take part in a chemical reaction; also, any electron in an atom except for those ib the core or in filled d- or f- subshells. In other words, electrons in open shells.
- Alkai Metals
- The elements in the first column of the periodic table (except hydrogen)
- Alkaine Earth Metals
- The elements in the second column of the periodic table.
- Atomic radius
- The radius of an atom
- Closed shell
- An electron shell which contains its maximum number of electrons.
- Covalent Bond
- A bond which involves the equal sharing of electrons.
- Double Bond
- four electrons, shared between two atoms.
- Electronegativity
- The tendency of the atom to attract electrons from a neighbouring atom.
- Electrostatic
- between two charged particles
- Groups
- sets of elements in given columns, going down the table.
- Hydrogen bond
- A bond which exists as a result of a strong dipole - dipole attraction between molecules having H-F, H-O or H-N bonds.
- Ionization energy
- the energy required to remove an electron from a neutral atom
- London Forces
- weak attractive forces which arise as a result of temporary dipolar attractions between neighboring atoms.
- Noble Gases
- Elements in the 18th column of the periodic table (headed by helium).
- Open Shell
- a shell containing less than its maximum number of electrons.
- Period
- The set of all the elements in a given row going across the table.
- Representative Elements
- The groups of elements which include columns 1, 2 and 13 to 18.
- Resonance Structure
- A structure, different from another only in the placement of alternating double bonds.
- Semiconductor
- a nonmetal, having an electrical conductivity, which increases with temperature. Semiconductors were formerly called metalloids or semimetals.
- Transition metals
- elements in columns 3 to 12 of the periodic table.
- Triple bond
- six electrons (three pairs_ shared between two atoms
- Valence
- The number of unpaired electrons in an atom: also called combining capacity.
- Van Der Waals forces
- A general term referring to any of the three types of weak intermolecular force, including the London Force, dipole - dipole force and hydrogen bonding.
- What are the four parts of Dalton's atomic theory?
- 1) Elements are made up of extremely small particles called atoms; 2)the atoms making up a particular element are all identical, and different types of atoms have different properties; 3)each chemical compound is unique and consists of a particular combination of specific types of atoms put together in a distinctive way; 4) chemical reactions involve the reshuffling of the atoms in a compound to make new compounds. The new compounds are made from the same atoms which are present in the original compound.
- How was Thomson's theory of the atom disproved?
- By Rutherford, with his Gold Foil Experiment.
- How can spectroscopy be used to identify unknown gases?
- Each gas has a unique structure, and each has to absorb a specific amount of energy in order to be transferred to a higher energy level, and emits a specific amount of energy when going back from the excited state, emitting unique wavelengths, resulting in the different colors and amounts of the spectra, which can be seen through the spectroscope.
- What is the difference between shells and subshells?
- Shells - a set of orbitals, having the same n - value; subshells - exist within the shells - a set of orbitals of the same type.
- What are halogens?
- The elements of the 17th group.
- What are lanthanides?
- The elements, transferred to the bottom of the periodic table, from Ce to Lu.
- What are actinides?
- The elements, transferred to the bottom of the periodic table, from Th tp Lr.
- List four properties of metals.
- shiny (with a luster); malluable and ducktile; good conductors; usually solid at room temperature.
- How does metallic character change when you go left to right across a period?
- it decreases.
- How does metallic character change when going top to bottom down a group?
- It increases.
- How does ionization energy change going left to right across a period?
- It increases.
- How does ionization energy change when going top to bottom down a group?
- It decreases.
- What's the difference between ionic and covalent bonds? (metals - nonmetals)
- Ionic - between a metal and a nonmetal; covalent - between two nonmetals.
- When are London Forces important?
- When they are the only forces of attraction existing between two species: a) adjacent noble gas atos, and b) adjacent covalently - bonded molecules
- What electronegativity do ionic bonds have?
- 1.7 or greater
- What electronegativity do Polar Covalent bonds have?
- Between 0.2 and 1.7
- What electronegativity do covalent bonds have?
- O.2 or less
- What are the two types of drawn schemes of ionic/covalent bonds?
- Ionic bonds don't share electrons, so there are only dots. Covalent bonds share electrons and dashes represent bonds.
- There are 2 bonds and 0 lone pairs. What is the name of the structure?
- Linear.