Basic Chemistry of Life exam study guide questions and answers.

atoms fundamental substance that has mass & takes up space protons found in the nucleus of an atom and are positively charged neutrons found in the nucleus of an atom and carry no charge electrons found circling around the nucleus and are negatively charged element has a unique # of protons in its nucleus atomic number the # of protons & neutrons the number of protons usually = the number of _____ electrons in the atom because the number of positively charged protons usually equals the number of negatively charged electrons the atom is ______ electrically neutral and has no net positive or negative charge mass number the total # of protons & neutrons do the number of neutrons and protons in the nucleus have to be equal? no elements that have the same number of protons but different numbers on neutrons Isotope examples of isotopes 12C= 6 neutrons, 6 protons ( the most common form) 14C= 8 neutrons, 6 protons (2 extra neutrons=radioactive carbon radioactive decay if an element has too many neutrons, it may be unstable and give off energy (radiation) to get rid of extra neutrons examples of radioactive decay 14C is unstable radioisotope that decays (gives off energy) until it turns into nitrogen 14N how do tracer studies work attach radioisotope to molecules & track where they go example of tracer studies in photosynthesis, plants release oxygen, where does the oxygen come from? 1 6H2O+6CO2 -> 6O2 +C6H12O6 is the chemical formula for photosynthesis experiment: use radioactive 18O (in H2O) instead of O and find 6H2O+ 6CO2 -> 618O2 +C8H1206 Interpretation: oxygen released into air by plants comes from splitting water H2O molecules not from CO2 shells where electrons orbit in the nucleus in a successive energy how much can the first shell hold 2 electrons how much can the second shell hold 8 electrons what happens when the outer shell is full the atom does not react or form chemical bonds with other atoms if the out shell is not formed ______ the atom wants to gain, lose or share electrons with other atoms by forming chemical bonds with other atoms to complete its outer shell what hydrogen is made of 1 electron in the first outer shell, but wants to. it is chemically active what is helium made of 2 electrons (first) outer shell. it is full. it is not chemically reactive what is oxygen made of first shell full, second shell has 6 but wants 8. chemically reactive what is carbon made of 6 electrons (atomic #) 2 in the first shell, 4 n the 2nd. forms up to 4 bonds Ion ion when an atom gains or loses an electron it becomes positively or negatively charged ionic bond when one atom gave an electron to another atom covalent bond atoms share electrons to complete their outer shells non-polar covalent bond two identical atoms share electrons equally and show no difference in charge polar covalent bond two or more different atoms share electrons unequally creating a positive side and negative hydrogen bond when hydrogen atoms locked into polar covalent bonds stick to other atoms that are negatively charged. hydrophilic water-loving hydrophobic water-hating- non-polar don't dissolve in the water b/c they have no charges to attract the water molecules oils and fuels _____ on water float how and why is water sticky____ water sticks to itself and creates a surface tension and this is because of hydrogen bonds water is a heat reservoir because______ water absorbs a lot of heat before increasing in temp.