Flashcards in Basics Deck (12):
what is the SI system?
The international system of units of which has 7 fundamental units (kg m cd s A K mol) - from which all other units can be generated
What is the purpose of significant figures?
Sig figs are this digits in a number that are meaningful to its precision
(To maintain precision)
Name the four subatomic particles and give their symbol, charge and relative mass
Proton, p, +1, 1
Neutron, n, 0, 1
Electron, e-, -1, 0
Positron, e+, +1, 0
Define atomic mass unit
1amu = ~1.66 x 10^-27 kg
Defined by setting the mass of carbon12 to exactly 12amu
How is atomic mass of an element calculated?
Atomic mass of an element is the average of the atomic masses and the abundances of each of the naturally occurring isotopes
The formation of new nuclei from existing nucleons
How are all atoms generated?
All atoms are generated from the simplest include, hydrogen, by nuclear reactions
How are stars created?
Clouds of atomic hydrogen are pulled together by gravity and heat as they are compressed. When temperatures rise high enough, the cloud ignites as a star
Give the overall hydrogen-burning reaction. Is it endothermic or exothermic?
2x H + H --> 2H + e+
2x 2H + H --> 3He + gam
3He +3He --> 4He + 2 H
4 H --> 4He + 2 e + 2 gam
What happens once a star exhausts its hydrogen?
It behind helium burning to fuse heavier nuclei forming increasingly larger atoms
4He + 4He + 4He --> 12C
Element forming reaction until iron are exothermic or endothermic and are produced where?
Heavier nuclei like 14N 15O are produced in red giant stars, still heavier nuclei in supergiants. New element forming reactions are exothermic until Iron. All elements up to iron are produced in stars.