Glossary of chem lab chap2
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- like charges__each other
- unlike charges__each other
- the spontanious disintegration of some elements into smaller pieces
- the three subatomic particle
- positive protons, neutral nuetrons, and negative electrons
- an atom's charge
- no net charge; the positive and negative balance each other.
- the # of electrons outside the nucleus=
- the # of protons within the nuclues
- three kinds of radiation
- alpha, beta, and gamma rays. when passed through electrically charged plates, they are attracted or repelled by them, proving they are electrically charged. alpha is heavier than beta so it is deflected less. positive alpha is attracted to neg plate and neg beta is attracted to pos plate. gamma rays pass straight thru, they have no detectable charge or mass.
- cathode ray
- glass tubes with little air and 2 metal electrodes. when a high voltage is applied to the electrodes, a cathode ray flows from the negative electrode (cathode) to the positive electrode (anode). cathode rays travel in straight lines and are attracted to positivly charged plates, like electrons.
- measuring electron's charge to mass ratio (sir joseph john thomson)
- he applied to the cathode rays, an electric field to deflect the electrons in one direction, and a magnetic field to deflect the beam in the opposite direction. by balancing the effect of the magnetic and electrical fields, the charge-to-mass ratio can be determined. this explains that electrons are present in atoms of all elements.
- electron charge determination (Milikan)
- droplets of oil fall into a chamber. xrays here ionize gas molecules (split them into electrons and a positive fragment). the electrons attach to the oil droplets, making them negative. a positive plate and a neg plate are adjusted to exactly counterbalance the attraction of the neg droplet to the pos upper plate. this leads to the value of the charge of the electron.
- canal rays
- (or positive rays) are particles traveling opposite to the cathode rays. electrons collide with gas molecules. the molecules become positivley charged and are attracted to the negatively charged perforated cathode. some pos particles pass thru the hole and form a beam or 'ray.'
- the alpha particles from the radioactive elements and the canal rays were too massive to be complimentary to electrons. rutherford found that hydrogen had the simplest possible structure with only one unit charge. he used the name proton for the first time.
relative mass- 1.007 u
- most atoms have masses greater than the predicted when it is only based on protons and electrons, suggesting there must be massive particles with no charge. credited to james chadwick.
relative mass- 1.009 u
- neg charge
relative mass- 0.0005 u
- atom compostion
- the atom is mostly empty space.
protons and nuetrons in nuclues.
# of electrons = # of protons.
electrons in space around nuclues.
- atomic number
- is the number above the name of the element. the number of protons in the nucleus of an element is the atomic number.
- relative atomic mass
- the real mass of atom is very small so its much easier to compare the mass of an element with another element. carbon is the standard.
- atomic mass unit (u)
- one atomic mass unit, 1u, is 1/12 of the mass of an atom of carbon with 6 protons and 6 nuetrons.
1u= 1.993 x 10^-23g/12= 1.661 x 10^-24
- mass number
- atoms of same element have same # of protons but diff # of nuetrons. the mass of a collection of atoms has an average value. average mass= atomic weight
- hydrogen isotopes
1 proton, 0 nuetrons
1 proton, 1 nuetron
1 proton, 2 nuetrons
- masses of isotopes- determined with a mass spectromere
- a sample of an element is introduced as a vapor into the ionized chamber. there, high energy electrons strip electrons from the sample. the resulting positive particles are accelerated by negatively charged plates into a chamber. this chamber is a magnetic field, perpendicular to the direction of the beam of charged particles. the magnetic field causes the beam to curve, its radius depending on the mass and charge of the particles.
- atomic weight
- (%abundance iso1 /100)x(mass isotope1)+ (%abundance iso2 /100)x(mass isotope2)
- 1 mole is the amt of substance that contain as many particles (atoms, molecules) as there are in 12.0g of C12
- avogadro's number
- 1mole= 6.022 x 10^23 particles
- moles to mass conversion
- moles x (grams/1mol)= grams
- mass to moles conversion
- grams x (1mol/ grams)= moles
- solids, can conduct electricity, are ductile (can be roled into sheets), can form alloys (solutions of one or more metals in another metal)
- with the exception of carbon, they do not conduct electricity
- group 1a
- alkali metals- all are metals and solids at room temp, all reactive.
- group 2a
- alkaline earth metals- metals that occur naturally only in compounds.
- group 3a
- contains al which resists to corrosion. ga is one of the few metals that can be liquid at room temp.
- atoms bonded to each other in more than one way, specific for some nonmetals
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